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Power Amplifier Gainclones more Gainclones Power Amplifier

2009-10-25T04:05:00.000+07:00

2x25 Watt LM1875 Gainclone Amplifier

2x50W LM3875 Gainclone Amplifier

2x56W LM3876 Gainclone Amplifier

2x68W LM3886 Gainclone Amplifier

2x50W Tube Gainclone Hybrid Amplifier

Build Power Amplifier LM3876, Simply and Powerfull Power Amplifier

2009-10-25T03:25:00.000+07:00

The chip on which the amplifier is based, a Type LM3876, is a member of the Overture family from National Semiconductor, All members of this family are pin-compatible and mutually interchangeable. They are typified by an internal protection (called SPIKE). In practice, the diftection ference between them is the power output. The series was described on the basis of the LM3886 in an earlier issue*.

The PCB has been designed so what it can accommodate the LM3876 (50W) as well as the LM3886 (150W). Because of this, pin5 of the IC on the board is connected to the positive supply line. This connection is not needed for the LM3876, since its pin5 is not (internally) connected (NC).

The IC is located at the side of the board to facilitate fitting it to a heat sink as shown in the photograph.

An important aspect for optimum performance is the decoupling of the unregulated supply lines by C 7-10. All earth connections go to a single terminal on the board.

Air-cored inductor L1 consists of 13 turns of 1mm dia. enamelled copper wire with an inner diameter of 10mm. The completed inductor is pushed over R7 and its terminals soldered to those of the resistor.

All electrolytic capacitors must be mounted upright. The amplifier can be muted with a single-pole switch connected to the MUTE input (pin8). This function is enabled when the switch is open. If muting is not required, solder a wire bridge across the mute terminals on the board.

Boucherot network R6-C6 is not normally required in this application, but provision has been made for it for use in other applications.

According to the manufacturers, both chips are optimalized for a load of 8 Ohm. The output power is lower when a 4 Ohm load is used or when the supply voltage is reduced. When a 4 Ohm load is used, the SPIKE protection becomes active when the supply voltage is about 27V, resulting a in a reduction of the power output to 10W. This means that it is not advisable to use loudspeaker with an impedance < 8 Ohm.

For best result you can expand power amplifier using BPA-200 Amplifier

Part list

Resistor:
R1, R3 = 1 k
R2, R4, R5 = 18k
R6 = see text
R7 = 10R, 5 Watt
R8, R9 = 22k

Capacitors:
C1 = 2.2 uF
C2 = 220 uF, 160 V
C3 = 22 uF, 40 V
C4 = 47 pF
C5 = 100 uF, 40 V
C6 = see text
C7, C8 = 100 nF
C9, C10 = 1000 uF, 40 V

Inductors:
L1 = 0.7 uH - see text

Integrated circuits:
IC1 = LM3876T

Miscellaneous:
Heat sink for IC1 < 1.5 K W-1
Single-pole switch - see text

Schematic and PCB Layout LM3876

Build Power Amplifier LM4780 with BPA-200 Amplifier

2009-10-24T01:36:00.000+07:00

This is design is very similar to the National Semiconductor BPA-200 (Bridge/Parallel Amplifier) which uses 4x LM3886 per channel and an input buffer:

Nothing Special in design but usefully for more watts!
My one will use 2x BrianGT LM4780 kits and a balanced line driver to bridge them, like this:

The LM4780 is a stereo audio amplifier capable of typically delivering 60W per channel of continuous average output power into an 8 load with less than 0.5% THD+N from 20Hz - 20kHz.
The LM4780 is fully protected utilizing National's Self Peak Instantaneous Temperature (°Ke) (SPiKe^TM) protection circuitry. SPiKe provides a dynamically optimized Safe Operating Area (SOA). SPiKe protection completely safeguards the LM4780's outputs against over-voltage, under-voltage, overloads, shorts to the supplies or GND, thermal runaway and instantaneous temperature peaks. The advanced protection features of the LM4780 places it in a class above discrete and hybrid amplifiers.

Each amplifier of the LM4780 has an independent smooth transition fade-in/out mute.
The LM4780 can easily be configured for bridge or parallel operation for 120W mono solutions.

The total effect is (2x LM3886's paralleled) x2 Bridged and should give approx 225 watts into 8 ohm and 335 watts into 4 ohm when used with a sufficient power supply.

The line driver part is based on the DRV134 and a PCB from digi01, you can see the details here.

In the end mine was dual mono in a recycled amp case using 2x 300VA (18VACx2) toroidal transformers, 54,400uF of capacitance per channel with a snubber. The DRV134s add 6dB of gain so I set the LM4780s to about 16x gain to compensate (they are set to 33 normally). I get no DC offset, no hum, no crackle or thump on turn on or turn off, silent as.

Pics.....

DIY Cat5 Speaker Cables

2009-10-06T08:44:00.000+07:00

These are perfect speaker cables for my brother speaker. I build use AMP Cat6 cables, for detail view here.

AMP Cable Cat6

TwistPair in TwistPair Cable Cat6

Ilustration wiring cable speaker using cable cat6

Perfect Sound Granite DIY Speaker Project

2009-10-06T08:21:00.000+07:00

I have been build this speaker for my brother, these are do-it-yourself (DIY) speakers that and using granite for the speaker box. I listen this speaker, That's Great Perfect Sound, nearly linear reproduction sound. Great Job Man!. Source Perfect Sound Granite DIY Speaker Project.

DIY Granite Speakers with Seas G17REX/P and 27 TFFC Drivers

Speaker Project Summary
External box dimensions 240 x 350 x 280 mm. Internal box dimensions 200 x 310 x 240 mm. Box material 20 mm thick black granite (Nero Assoluto). Weight 35 kg.
Enclosure volume 14.9 L. Bass reflex enclosure tuned to 45 Hz. Port length 160 mm
Input power 80W. Sensitivity 87.5 dB. Transmission bandwidth 40Hz - 20kHz. Impedance 6 ohm.

Seas Granite Speaker Enclosure Plan

Seas Loudspeaker Drivers
The drivers selected for this loudspeaker system are from Seas who has been producing speaker drivers for over 50 years. The tweeter is the Seas 27 TFFC which has a fabric dome. The Sonolex lightweight fabric dome has high consistency and provides excellent stability against variations in air humidity. The stiff and stable rear chamber allows for a moderately low crossover frequency (~2500kHz). This made the Seas 27 TFFC tweeter the right choice for our granite loudspeaker project.

The woofer we used is the Seas G17REX/P. The woofer consists of a fiber glass cone, a bullet shaped phase plug and a high loss rubber surround. These are carefully matched to each other resulting in smooth frequency response.

Speaker Box and Crossover Design
The speaker box and crossover network were designed by M.Janura and K.Sýkory using the LspCAD speaker design software package. A volume of 15L (dimensions 220 x 350 x 250 mm) and a tuning frequency of 45 Hz was used for the speaker box. The dividing frequency is 2.5kHz and the drivers are connected in phase. The crossover schematic and modeled frequency response are shown below.

Calculated Speaker Box Frequency Response - Seas G17REX/P Woofer

Crossover Schematic - Seas G17REX/P Woofer and 27 TFFC Tweeter

The components used in the crossover dividing network are from TESLA. I think that the people in the former Czechoslovakia were able to produce high quality components, but you may use your favorite type. The condensers (capacitors) used in crossover are MKT type - we did not use bipolar condensers because they have disadvantages that I won't further specify. The inductors are air core.

Sound

I was knocked off my feet with the sound after the first track we played: Everlast - Folsom Prison Blues by the legendary Johnny Cash. The song tested bass response of the speakers. We didn't expect such deep and accurate bass from small speakers. The speakers deliver very detailed sound (soft treble and great imaging). They play rock music aggressively and classical music with emotion. As we say: "they play like HONEY" (it means - brilliant) and they look great too.

I would like to thank to Marian Mózer and everyone in the team for their effort and for the job well done. The loudspeaker system is designed by M.Janura and K.Sýkory - named Besie 1.

We understand that most of you will not be able to make speaker boxes of granite. If you are interested in speakers made from granite, please send me an email and we may be able to help you. Thank you and I hope you enjoyed our project.

Seas Granite Speakers

Single Ended Class-A Power Amplifier using 6C45Pi

2009-09-28T22:59:00.016+07:00

The valve itself, have a simple circuit enviable any transistor amplifier, however, not many projects that employ a single active component. This construction philosophy, I like to call it minimalism.

If one speaks of minimalism, I think, that this project has all the credentials to qualify as such.

This is an amplifier cu, a final integrated (Compact) which employs a single tube (triode) signed 6C45Pi. To do this, could be used several tubes, including 437A, E55L (pentode) and the fantastic and expensive EC8020.

Two lines must for this valve: The EC8020 has an exceptional linearity, high dissipation and trasconduttanza worthy of a power triode. All factors ideal for a good amplifier cu, were it not for the prohibitive price (on the ebay Offers easily exceed one thousand dollars!).

6C45Pi even if does not reach the performance of EC8020, performs the task with dignity. The cost is a couple of orders of magnitude lower and is currently produced by Electro Harmonix and is part of his series most valuable the Gold Pins.

Schematic Diagram

The circuit used setup is classic: single-ended. This choice leads to a lower power, an output transformer more expensive, but all will benefit, at least for my taste, the sound quality.

shematic-Single-Ended-Class-A-Power-Amplifier-using-6C45Pi

About nutrition, the first idea was to use, such as straightening, a valve, but with an excessive size of the Schottky diode and filtering capabilities have also obtained excellent results (Sonic).

PCB

Not many projects are implemented on printed circuit valve, but it is my strong belief that, 's addition to a more orderly construction, provides added value to the success of the project.

The layout is as follows:

PCB-Layout-Single-Ended-Class-A-Power-Amplifier-using-6C45Pi

A fundamental rule in the design of the board is to avoid any link mass, so you should use as much as possible in a star structure. Usually the star center coincides with the negative of the first capacitor filter.

Realization

The board:

I used the usual method of iron more HCl + H 2 O 2.

Four resistors are metal film for half a watt, those from 220ohm wire wound vitreous enamel coated 6W, the Panasonic FC Electrolytic low impedance. Alps potentiometer, then the diodes, as already mentioned, type Schottky 1000V 1.5 A.

The two TU are wrapped by the Company upon specific ATC Electronix: www.atcelectronix.com/ provides the following features:

Primary: 4000 ohms
Secondary: 6 ohms
Power: 10W
Grain-oriented core AC 0:35
Bandwidth: 15 Hz - 75 KHz

I like to use for my projects output transformers wound on specific, because I have the opportunity to obtain more than I seek., The kind Mr. E. Calabrese's ATC Electronix has been immediately available, we discussed the characteristics and came quietly meeting.

Mechanically, the TU are well made, sturdy, beautiful black ice caps, we see that there is the hand of a fan.

Some photos of finished:

The cabinet is birch plywood 10mm polished with wax. I like the effect that old yellow comes out. The photos do not make the idea of greatness, but it is really small, only 230 x 200 mm high 60mm (TU and TA excluded).

I suggest to the speaker terminals, derived from a larval bi-wiring connections, it was a very economical way to get the four terminals, buying in bulk would have cost me more.

The cable used for connections between RCA, potentiometer and card is excellent Belden.

Listening

A valve, one triode and yet it sounds. Thought of having to keep the volume potentiometer can to listen to a decent level, but it was not at all. The pot did not exceed half of the race than I shouted down ... but we are talking about a "paltry" Watts!. Certainly the BLH (FE108ESigma) have done their bit (90 dB / W efficiency).

I connected everything, turned on and my room was immediately filled with music. Main features: detail, depth and dynamics.

Everything I heard sounded really good, thanks not only 6C45Pi but also of TU ATC Electronix.

The Finaly I am deeply moved, usually happens at concerts and my master amplifier.

The Medes and the voices are spectacular. I listened to all possible kinds of vocal music. Each of them seem natural, male or female is.

From Jazz to Classical, dall'Acustica the Rock and anything there is in the middle, everything comes back perfect. This little amp is very transparent.

Having experienced the one-tube amplifier, I had the confirmation: I will be forever minimal! Few watts, or only a few components in the audio chain, single screw speakers, no cross-over, no feedback, just pure music!. An amp like this, a simple player, a pair of single screw is all that a person has (or should have) need. I am extremely satisfied, so much so that I could separate me from my SE with the 2A3 and not feel greatly missed.

Faults? Sure. The sensitivity is very high, indeed it is low for maximum power output must be driven by almost 5 Vpp. The dynamic is good, but only one watt is just for musicians. However, the little man is promoted with flying colors while remaining down to earth.

(Source: http://digilander.libero.it/giovannidefilippo/progetti/GDF-UNICO!/UNICO.htm)

Promitheus Hexfet Power Amplifier

2009-09-27T02:26:00.004+07:00

Here you can find the whole article of the Elektor magazine of the new upgraded Hexfet amp. The new amplifier uses bigger output devices, IGBTs in T0-247 Package. It has more power and uses new technology transistors. These transistors are insulated gate bipolar transistors (IGBT). They have an input like a FET so the work with voltage and they handle current like a bipolar.
Look here for The IGBT or HexFet amp.

I used the same board for my own upgrade. I used the higher power supply voltage of the second edition for IGBTs but since I didn't like to use IGBTs (I am a great fan of MOSFETs) I went on and used bigger Mosfets instead in TO-247 P case. I used the IRFP250 and IRFP9250 from Intersil/Harris. They are very cheap and reliable. The IR are the same too. IGBTs are a lot more expensive. This amplifier is great with very good sound and a lot of power for all kinds of speakers.

Modification

The original design already allowed for a higher-output version, whence the duplicated holes for the output transistors on the printed-circuit board. At that time, advance information on the IGBTs was already available, but samples were not.

Although IGBTs are quite different from HEXFETs, the board for the original design can be used without any modification. In fact, the circuit has hardly changed. The most noticeable alteration is the replacement of the fuses in the source lines of the power FETs by emitter resistors for the IGBTs. The only other changes are in the value of two resistors in the compensating circuit of the input stage, of one in the quiescent-current circuit, and of one resistor and two capacitors in the protection circuit.

This means that anyone who has built the original HEXFET amplifier can quickly modify it to the upgraded version. One item needs to be replaced, however:
the mains transformer. After all, more power can not be obtained from the same supply voltage/current. The original transformer with 2×25 V secondaries must be replaced by one that provides 2×30 V at 3.75 A. This will result in a direct voltage of ±43 V.

Ceramic speaker driver amplifier design

2009-09-09T22:32:00.009+07:00

Today's portable devices contributed to the smaller, thinner and higher efficiency of electronic devices needs. Now cell phones have become very slim shape, so that the traditional electric-powered loudspeaker has become a mobile phone manufacturers can create as many thin constraints. Ceramic or piezoelectric speakers is rapidly becoming a viable alternative to electric-powered loudspeaker device. These ceramic speakers (drivers) can be slim and compact package provides a very competitive sound pressure level (SPL), which most likely alternative to traditional electricity-powered loudspeaker voice coil.

Ceramic speaker driver amplifier circuit and drive the traditional electric-powered loudspeaker amplifier circuit compared to a different output drive requirements. The structural requirements for ceramic speaker amplifier is capable of driving large capacitive loads, can provide more current at high frequencies, while also able to maintain a high output voltage.

The characteristics of ceramic speakers

Ceramic speaker manufacturers use the technology is very similar to the manufacture of multi-layer ceramic capacitors used in technology. Compared with the electric-powered loudspeaker, the loudspeaker manufacturing technology enables manufacturers to more stringent control over the speaker tolerances. Speakers you want a unified and agreed upon the acoustic characteristics, the rigid structure of tolerance is very important.

As can be seen from the driver amplifiers, ceramic speaker impedance can be modeled as an RLC circuit, it comes with a large capacitor, this large capacitor is the main component of the model shown in Figure 1. For most audio frequencies, the ceramic speaker is manifested mainly capacitive. This capacitive characteristics of the speaker to express its resistance will decrease with increasing frequency. Figure 2 shows the similarity with 1uF ceramic capacitor speaker impedance and frequency characteristics.

Figure 1. Ceramic speaker models.

Figure 2. The speakers and 1uF ceramic capacitor impedance and frequency characteristics.

The resistance also has a resonance point. Speakers at the resonant frequency above the audible most efficient point. Decrease in the impedance at 1kHz speaker expressed the resonant frequency.

Relationship Between Sound Pressure, Frequency and Amplitude

The two ends of the ceramic speaker to exert an alternating voltage can make the internal speakers of piezoelectric thin film deformation and vibration, the displacement distance is proportional to the input signal. Vibration of the piezoelectric film to promote the surrounding air, resulting in the sound. Improve the speaker can increase the voltage on the piezoelectric element deflection amplitude, resulting in a greater sound pressure and thus can increase the volume.

Ceramic speaker manufacturers maximum voltage tends to be used to mark their speakers, usually around 15Vp-p. Ceramic devices, said the largest voltage reaches the maximum extension. If the applied voltage is higher than the rated voltage does not produce a higher sound pressure, but it will increase the output signal distortion, see Figure 3.

Figure 3. Frequency Characteritics of Sound Pressure Level.

By comparing the SPL and the frequency and impedance versus frequency curve can be seen in self-resonant frequency of piezoelectric speakers have a large SPL above the most efficient.

Amplifier Requirements.

Ceramic speaker manufacturers typically provides 14 to 15Vp-p of the point of maximum voltage to produce the greatest value of sound pressure. The question now becomes how to generate a single battery supply voltage of these voltages.

One way is to use switching regulators to raise the battery voltage is 5V. With a stable 5V voltage, the system designer can select a needed bridge-tied load (BTL) for single-supply amplifiers. Connected through the bridge can be automatically loads the voltage speaker to see double.

However, the BTL amplifier with 5V output swing theory can only give rise to 10Vp-p. The voltage is not enough to make ceramic speaker output value of the highest SPL. In order to generate higher sound pressure values need to be adjusted to a higher supply voltage.

Another method is to use the boost converter to the battery voltage rises to 5V or higher, but it also has its own problems, such as component size problem. Large peak inductor current will be restricted the size of the overall solution, because in the end of the inductor size must do in order for the physical size of large core is not saturated. Although the small size of the inductor-current market, there are, but the core's saturation current rating may not be sufficiently large to satisfy the high-frequency high-voltage-driven speaker when the load current demand required.

Because ceramic speakers at high frequencies with very low impedance, so when you drive the ceramic components to take into account high-current drive and to avoid the limit.

Chosen to drive the ceramic speaker amplifier must be large enough to drive current in order to avoid driving a large number of high-frequency component of signal-driven speaker into the current limiting mode.

Figure 4 is a Class G amplifier using the application circuit. Class G amplifiers are available multiple voltage rails: a high-voltage and a low voltage. Low-voltage rail used in the output small signal, when the output signal demands for higher voltage swing, the high-voltage rails were switched to the output stage circuit.

Figure 4. Schematic amplifier Class G

Thus, when the output signal is small, G amplifier efficiency than Class AB amplifiers high, due to a lower voltage rail. Because there is a higher voltage rail, G amplifier can still handle the peak transient signals.

Shown in the figure uses a MAX9788 on-chip charge pump to generate a negative voltage and the VDD opposite. The negative voltage rail only require a higher voltage output signal when added to the output circuit on the rail. Boost converter and method of using the traditional Class AB amplifiers, the device can be more efficient to drive ceramic speakers.

Loudspeaker manufacturers often recommend and ceramic speaker series with a fixed resistor (RL), as shown in Figure 4. The resistor in the signal that contains a large number of high-frequency components can limit the amplifier output current.

In some applications, if the restrictions sent to the speaker of the audio frequency response of bandwidth to ensure that the speaker is not short-circuit of the amplifier, you can not have this fixed resistor. Ceramic speakers currently on the market value of the 1uF capacitor of magnitude or so. Speaker as the impedance at 8kHz when 20W, at 16kHz when 10W. Future ceramic speakers may have a larger capacitance value, will force the signal amplifier at the same frequency to provide more current.

Ceramic speaker and the efficiency of electricity-powered loudspeaker.

The efficiency of traditional electricity-powered loudspeaker is easy to calculate. In electrical windings on the coil can be modeled as a fixed resistor in series a large inductor.

You can use the speakers resistance value calculated in accordance with Ohm's law to provide power to the load:

P = I2R, or P = VxI

The power consumption of the speaker coil heat.

As the ceramic speaker's capacitive characteristics, they are power consumption when not produce too much heat. According to the dissipation coefficient of ceramic components, such speakers consumption of so-called reactive power (blind power) is very small. Therefore, the consumption of reactive power generated when the heat is very small.

Can not use a simple calculation of P = VxI reactive power

Reactive power should it be calculated as follows:

P = (πfCV2) × (cosΦ + DF)

Where: c = capacitance value of the speaker; v = RMS driving voltage; f = the frequency of driving voltage; cos j = "current through the speakers, and speakers on the phase angle between the voltage"; Df = speaker dissipation factor, depends on the signal frequency and ceramic speakers ESR.

For an ideal capacitor, the voltage and current between the phase angle should be 90 degrees, while the ceramic speaker is mainly capacitive characteristics, so cos j is equal to 0, that is not part of the ceramic speaker's capacitive power. However, the non-ideal characteristics of ceramic materials will lead to lag behind the voltage on the speaker through the speaker of the current phase angle between them is not equal to 90 degrees. The ideal 90-degree phase shift and the actual difference between the phase shift is the dissipation coefficient. Ceramic speakers in the Df can be modeled as a small resistance, ESR, and an ideal capacitor in series. (Do not series resistance and the isolation between the amplifier and speakers to confuse resistance) Df is the target frequency, the ratio of ESR to the capacitive reactance (Reference 2 and 3):

DF = RESR / XC

For example, a 1.6uF capacitor and the speaker 1W ESR being 5Vrms, 5kHz signal when driving reactive power is:

P = (π × 5000 × 1.6e-6 × 52) × (0 + 0.05) = 31.4mW or 31.4mW.

Real Power

Thus, while the ceramic speaker itself does not like the electric-powered loudspeaker, as the actual power dissipation by thermal methods, but the driver amplifier output stage, and is located between the amplifier and speaker external resistor (RL) could give rise to heat (Figure 4).

An external resistor the greater the amplifier will generate more power, thus affecting the low-frequency response.

In the drive with a 10W series resistance of the ceramic speaker, we can see that the reactive power has little effect on total load power. Most of the power consumed by an external resistor, see Figure 5 shows the amplifier power and frequency curve.

Figure 5: the necessary relationship between power and frequency

Better low-frequency response for a smaller external resistor, but this will cause the amplifier output stage power consumption increase. Amplifier efficiency shows how much power consumption in the amplifier output stage. Driven right amplifier power, including class and G class D amplifier, including the demand for more efficient solution, due to the load formed by a number of series resistance, it will load on the network rather than the speaker to generate a certain power. Even if the efficiency of 100% of the amplifier, series resistance will be consumed is supposed to give the speaker power.

In this simple example, 5kHz provided to the load point of the total power is 515mW. Efficiency of 53% of the amplifier will consume 457mW of power. The necessary power amplifier the size of the device can determine the size of the package used. If you must use high-frequency sine-wave-driven speaker, it requires a great deal of power.

In short, the increasingly thin portable devices contributed to the small size ceramic speaker needs. This speaker is different from the traditional electricity-powered loudspeaker, so designers need to consider different design elements. Ceramic speaker's capacitive properties require amplifiers with high output voltage drive and large output current capability, so that the entire frequency range in order to maintain a high voltage.

Chosen to drive the ceramic speaker amplifier must be able to mix the load while providing reactive power and real power. Amplifier efficiency must be high enough to ensure small size and low cost programs.

Therefore need to use different from the traditional Class AB amplifiers amplifier topology. For example, Class G and Class D amplifiers and other more efficient solutions are becoming more attractive, in which G amplifier can provide the best efficiency.

Translate from http://www.eeworld.com.cn/mndz/2008/0625/article_52.html

LM3886 Power Sub Woofer Amplifier

2009-09-06T00:01:00.003+07:00

I found this schematic, LM3886 Power Sub Woofer Amplifier. Maybe next time, I'll share the results this amplifier.

Dual-band CDMA-EVDO and WCDMA-HSDPA Power Amplifiers

2009-09-05T09:22:00.010+07:00

ABIResearch According to a recent report (1), wireless mobile data for the European contribution to a large number of operators in 25-30% of their income for Japan's contribution of up to 38% of operators revenue. This wireless data services, such as music downloads, e-mail and the increasing popularity of mobile Internet users and mobile broadband data services revenues to compensate for declining voice usage per user. Therefore, operators around the world are turning their 2G voice-oriented technology, upgrade their networks to 3G and 4G technologies, to enable them to provide high-speed, broadband wireless data services to consumers and business users.

CDMA / EVDO and WCDMA / HSPA is the most widely deployed 3G technology, the two. The two techniques depends on the Code Division Multiple Access (CDMA) digital wireless technology, so that many users can be effectively used with a radio-frequency spectrum of the voice and data communications. CDMA is a species rely on a unique "cut code" assigned to each user spread spectrum radio communications, in order to distinguish in the same RF spectrum of the other users. The spectrum to expand the channel capacity increases and allows multiple users to use the full bandwidth of operators. CDMA / EVDO network operators 1.25MHz, and WCDMA / HSPA network to use a wider range of 5MHz. Data transfer rate can also be in wireless networks to further increase high-level modulation to provide a better user experience and wireless data.Multi-band CDMA and WCDMA mobile phones the need for greater RF design work in order to provide sufficient output power and to ensure the linearity and efficiency of the normal operation of each band. Design usually includes a power amplifier and favorable duplex of each frequency band, RF filters and switches to meet the multiple RF input to a single antenna. In order to reduce the multi-band mobile phone design complexity, ANADIGICS硑made a dual-band CDMA and WCDMA power amplifier module. Integrated in a single package through the two power amplifier modules, and before the use of two separate DC and RF power amplifier design of signal lines in comparison, which can effectively reduce the circuit board area. This article will describe the dual-band power amplifier module in the CDMA / EVDO and WCDMA / HSPA mobile phone designed for typical application.

This article will focus on ANADIGICS AWT6221 in UMTS paragraphs 2 and 5-band, dual-band WCDMA / HSPA mobile phone design applications. The AWT6221 has won ANANDIGICS by the Chinese Ministry of Information Industry issued by the application of information technology, communications technology Outstanding Innovation Achievement Award (2) and EDN Innovation Award, communications and network product excellence award.

AWT6221 dual-band power amplifier significantly reduces power consumption up to 75% of the average current, and increase up to 25% of talk time.

ANADIGICS of HELP3™ power amplifier, such as AWT6221 power amplifier uses the company's exclusive InGaP-Plus ™ technology, in the same InGaPGaAs die, which integrates bipolar and field-effect transistor (FET) devices. Through selectable bias modes, HELP3 ™ power amplifier in the low range and mid-range output power levels in the present the best efficiency. Intelligent bias circuit of AWT6221 down at low power levels can be reduced to 8 milliamperes current power - best in the world. By integrating two separate amplifier chains, super-mini AWT6221 in these two frequency bands to provide superior performance, and save the printed circuit board area. (Figure 1)

ANADIGICS company is a combination of popular band dual-band WCDMA / HSPA Power Amplifier Module for CDMA / EVDO applications, dual-band power amplifier module. More information can be found ANADIGICS Inc. ANADIGICS company has developed a reference design products to help customers faster, easier to achieve their design goals. In this article we will describe the AWT6221 (Figure 2) reference design advantage.

Figure 1. Schematic AWT6221RDAFigure 2. Prototype AWT6221RDA

AWT6221 is a dual-band WCDMA / HSPA mobile UMTS band 2 (824-849MH) and band 5 (1850-1910MHz) and developed. 3GPP technical specification of the user equipment level 3 power, must meet or exceed these minimum performance levels (3)

Maximum output power: +24 dBm +1 /-3dBm
Adjacent Channel Leakage Power Ratio (ACLR) + /-5MHz:-33dBm
Adjacent Channel Leakage Power Ratio (ACLR) + /-10MHz:-43dBm
Frequency :30–1000MHz:-36dBm/100kHz

In the between 1-12.75GHz: -30dBm/1MHz
In the between 869-894MHz: -60dBm/3.84MHz
In the between 1930-1990MHz: -60dBm/3.84MHz
In the between 2100-2170MHz: -60dBm/3.84MHz

Most of the CDMA and WCDMA networks, frequency-division duplex systems allow different radio frequency bands allocated to the uplink (from mobile to base station) and downlink (from base station to mobile) link at the same time. Duplexers for mobile devices to allow the UL and DL use a single antenna. UMTS band 2, we have chosen to Avago Technologies FBAR duplexer micro-high-Q response to ACMD-7403. For Band5, we have chosen to Epcos low-loss SAW duplex B-7663. The reference design also includes thin-film power directional coupler CP402A coupling AVX, for a number of top-3G chipset to provide the required RF power.

AWT6221 the development of reference design starting in the power amplifier to further coupling with the duplex S parameter measurements. In this measurement, the zero-ohm resistors are used to shorten the circuit board matching components (Figure 3).

Figure 3. Schematic Diagram AWT6221RDA

Describe the N-port S parameters for each one-port network response of the voltage signal. The first number of the subscript refers to the response to mouth, while the second figure refers to the case mouth. S21 refers to the signal side, therefore a result of two reactions in the mouth. S parameters of an equal number of rows and columns from the matrix port. S matrix along the diagonal of the parameters are known as the reflection coefficient, diagonal S parameters are referred to as transmission coefficients, because they only occur in a single port. S matrix of two-port network in the table below:

Reflection coefficient (S11) for band 2 and band 5 the frequency range of RF paths to test. Power amplifier at the output of the circuit is not in line with the formation of a series of impedance changes, the results displayed in the Smith form (Figure 4, Figure 5).

Figure 4. Cell Band: PA output to Antenna

Figure 5. PCS Band: PA output to Antenna

For any power amplifier, the output impedance have a major impact in the operation, and a strong influence on the transfer to the antenna, linear (ACLR) and operational efficiency of power. ANADIGICS power amplifiers as the vendor can help engineers to do a good job balancing the load-pull of information. Optimum output impedance will be other characteristics of RF chain, the influence of components such as diplexers and switches are not always 50Ω. Variation frequency band characteristics of the advantages of duplex and operating temperature, in well-developed WCDMA RF design, particularly challenging.

Designed with Discrete Components, Complementary Symmetry Power Amplifier

2009-09-05T07:14:00.006+07:00

1. Power Amplifier Basic Circuit Characteristics

Complementary symmetric OTL amplifier basic circuit as shown in Figure 1. Where: C1 for the signal input coupling element, should be noted that the actual circuit in the polarity should be consistent with the potential situation. R1 and R2 bias circuit composed of BG1, BG1 to provide a static operating point, but also in the entire circuit to play the role of DC negative feedback. Asked to approve R1 is greater than the current BG1 base current of at least five times, according to β is 100, Ic1 for 2mA calculation, R1 should be no more than 6k, it is given as a 5.1k; C1 accordingly, to set at 22μ, it is 20Hz signal on the impedance of 362Ω; R2 must be in accordance with the specific voltage of the power to determine, or about R1 (E/2-0.6) / 0.6, in accordance with 32V voltage value should be taken as about 120K, the exact value of the actual debugging by making BG1 collector voltage of 15.4V to get.

C2 and R3 constitute a bootstrap circuit, require R3C2> 1 / 10, (R3 + R4) Ic1 = E/2-1.2, due to the exchange of R4 is the BG1 load resistance, as far as possible to take bigger, R3 normally taken within the 1k. In accordance with 32V supply voltage value and Ic1 to 2mA calculations, R3 and R4 of and for the 7.2k, the actual will of R3 to 820Ω, R4 to the 6.8k, Ic1 compared to 1.94mA; C2 is therefore desirable to 220μ.

R5 and D are BG2, BG3 complementary bias control circuit components, to BG2, BG3 together provide a suitable quiescent point, to eliminate crossover distortion as much as take a small value, according to the experimental results are generally obtained in the 3mA ~ 4mA; R5 Resistance to change can BG2 and BG3 base voltage drop between the changes in the work to achieve the adjustment of its static, and R5 in series D is to compensate for BG2, BG3 launch junction threshold voltage changes with temperature, preferably in two only the series diode junction fired up and compensate for the threshold voltage of complementary tube changes with temperature, so that complementary management quiescent operating point stability. Omitted to simplify the use of a diode circuit. In parallel with BG2, BG3 base between the C4, can reduce the dynamic work of the ΔUAB, generally taken to be 47μ; C3 is to prevent the BG1 the exchange of high-frequency self-excited negative feedback capacitor, generally taken to be 47P ~ 200P.

BG1 from voltage amplification role in this circuit is known as the incentive level, require Buceo> E, Iceo ≤ Ic1/400 = 5μA, β = 100 ~ 200, so it should use low-power low-noise transistor. BG2 and BG3 are complementary current amplification pole, respectively, and BG4, BG5 constitute a composite tube to amplify the output current require Buceo> E, Iceo ≤ Ic2/100 = 30μA, β = 100 ~ 200. In the BG4, BG5 using ordinary high-power tubes instead of three has been made within the composite pipe under high-power 3, BG2 and BG3 need to provide the post-class high-power three tubes of more than 100mA peak drive current, it should the use of power three tubes. BG4 and BG5 is responsible for the amplification of high-power output current control, quiescent current is desirable in the 10mA ~ 30mA, asked Buceo> E, Iceo ≤ Ic4/100 = 0.1mA, β = 50 ~ 100. BG4 and BG5 the maximum limit of current Imax should be greater than the largest amplitude of the output current times the big one, can ensure the maximum amplitude of the output current when β> 10.

R6 and R7 are BG4 and BG5 quiescent operating point adjustment of shunt resistor, the dynamic work of the streaming effect can be negligible. The Ube4 and Ube5 are equal to 0.6V standard parameters, by the complementary current amplification level obtained in the static working current of 3mA ~ 4mA, calculate the R6 and R7 should be taken as 220Ω. In fact, the power may be a difference of three tubes Ube larger, BG4 and BG5 of Ube be carried out by matching the measured use of the bootstrap circuit to work with half the total current magnification composite pipe shall be constructed without the aid of the work of the bootstrap circuit The other half of the composite pipe is smaller.

R8 and R9 are to prevent the BG4 and BG overcurrent limiting resistor, generally take between the 0.2Ω ~ 0.5Ω. Will use the 200mm long, diameter φ0.08 both ends of the enameled wire were welded over the 1k resistor at both ends to fold up enameled wire can be wrapped around the resistor. Is equivalent to the role of fuse fuse belongs to the simplest non-smart Limit blown protection methods.

C5 and C6 is the signal output capacitor, with a small capacitor in parallel with the large capacitor up and use, it can eliminate large-capacity capacitor has a larger internal inductance for high-frequency signals obstacles. Note that it is actually played the role of the mid-point of floating power supply, so power is not in accordance with the capacity to fight with a right pass the bottom of AC impedance of the signal should be how to calculate, but according to how much energy consumption of the output power required is calculated. In the mid-point of the floating power supply voltage fluctuations as a result of the output current cut-off wave output signal, they will have serious clipping. According to the energy storage capacitor voltage is proportional to the square with the relationship between the midpoint of the floating power supply output capacitor, the total power supply capacity should be 4 times the energy storage capacitance.

C9 and R10 is the exchange of negative feedback network, and R2, R1 together form the voltage in parallel with negative anti-ashamed. R2 and R1 anti ashamed constitute a negative DC voltage allows the total magnification approximately equal to R2 divided by 1.2k (equal to R1 with the launch of BG1 junction dynamic resistance in parallel), the design parameters in accordance with Figure ① about 100 times, adding C9 and R10 After the exchange of negative feedback network, the total voltage magnification approximately equal to R2 and the R10's parallel resistance divided by the 1.2k, is about 18 times. Practice has proved that the work in this way the voltage performance of parallel negative effects of anti-ashamed very good.

2. Improvement of Basic Circuit of the Power Amplifier

As shown in Figure 2, complementary symmetric OTL amplifier basic circuit, the signal input level resistance incentives only 1k, impedance needs to be done in order to transform the vast majority, the high impedance signal source match. Incentive level direct the signal input into a composite pipe is the easiest way to composite pipe connected in a variety of specific circuit. Additional pre-class practice is equivalent to a simple voltage-controlled current-mode operational amplifier, BG0 the base and the emitter is equivalent to op-amp positive input and negative input, positive input of the dynamic resistance has been increased to more than 10K. Meanwhile, the output from the power amplifier receiving the negative input emitter of negative feedback resistor R10 and sampling resistor R11 determines the ratio of the total voltage magnification.

Debugging is also the first points of the circuit R5 adjusted to short-circuit resistance status of 0 to BG2 ~ BG5 in a cut-off state, respectively, with two 1K/2W resistance received from the total power output at both ends to obtain the midpoint voltage. Instead of using a 200K potentiometer R1 or R2 connected to the circuit board, with wires to the input signal input capacitance C1 and ground short-circuit.

Connected to power, measure BG1 of the collector to emitter voltage drop Uce, regulation allows Uce equal to 200K potential E/2-0.6; in the total supply voltage of 32V, when, BG1 static Uce should be equal to 15.4V(0.1V). Then measured the actual 200K potentiometer in which the resistance value, replace the fixed resistor with resistance potentiometer replacement, and then measuring BG1 static Uce should 15.4V(0.2V) within. To determine the static Uce good BG1 again after small to large BG4 and BG5 adjust R5 so that the quiescent operating current of 15mA. For insurance purposes, R8 and R9 can be for access into 100Ω/2W resistors, R8 and R9 on the first measurement of the static voltage drop should be 1.5V.

Disconnect the power supply, measuring the actual resistance of R5 in which adjustable resistor values, resistor R5 into the same fixed resistors, removed earlier from the output side are connected to the power supply at both ends of 1k/2W divider resistors. Re-connect power, R8 and R9 on the measurement of the static voltage drop should be maintained at between 1.2V ~ 1.8V. Measuring the output level should be the midpoint between the 16V(0.5V). The C1 input capacitance signal input terminal and the earth floating disconnected, measure the voltage drop R8 and R9, C1 encounter with the screwdriver when the input voltage on R8 and R9 dropped significantly larger. And then replace the 0.3Ω resistors R8 and R9, connected to the horn Lyrics. Connected to the power due to C0 charge, midpoint voltage of the output needs to rise slowly from zero, which produced only a slight impact on sound. When the hands touch the C1 input speaker will issue a "woo" the exchange of sound. The C1 input and ground (negative power supply side) short circuit, speakers should not sound, the actual will be issued by a slight background of white noise or very low voice communication hum.

As shown in Figure 2 complementary symmetry power amplifier improvement type OTL circuit, there is a clear disadvantage is that the input signal DC level than the midpoint of the output voltage is lower 2V ~ 3V, not in the public use and transistor op amp IC components, the high cost of the 20th century, early 80s, it has very good power amplifier using a single power supply practical circuit. The mid-20th century, 80, op amp IC, starting, people began to use pre-op amp IC to serve as a very great and inspiring.

A typical circuit shown in Figure 3 due to op amp IC do not need to adjust the static working point, as long as BG2 ~ BG5 adjust R5 so that the quiescent operating current of 10mA ~ 20mA can be. Note that, although the op amp IC do not need to adjust the quiescent point, but in BG2 ~ BG5 in a cut-off state, from R8, R9, and BG3, BG5 emission knot is wizard-pass will be the negative input of op amp IC is set to high, transport, Z IC output is low, then fired through the BG3 junction to the negative input of op amp IC is set to low, the output of op amp IC turning into a high, resulting in the output variable of the low-frequency oscillation state can not provide a stable The reference to the midpoint level.

In this situation, adjust the BG2 ~ BG5 quiescent operating current, op amp IC output is high when the regulator R5 is invalid; while IC op amp output to '0 BG5 can not turn to regulate the R5 can only BG2, BG3 , BG4 to enter the work area, BG2 actually only played the role of the diode by BG4, and BG2 the current direct all poured into the op amp IC output, resulting in BG2, and op amp IC damage due to over-current! (I have to hand at that time owned by a few domestic op amp IC and a dozen medium-power three pipes all the damage, but also failed to adjust the quiescent operating point out.) Must first IC op amp with a wire to the negative input and output connectivity, temporarily connected to the negative feedback resistor R6, so that op amp IC in follower mode output stability level of the mid-point of reference, in this state, adjust R5 so that BG2 ~ BG5 the quiescent operating current of 15mA, the R5 resistance into the same fixed resistor confirm BG2 ~ BG5 quiescent operating current of 10mA ~ 20mA in between, and then the negative op amp IC input and output end to end open, the feedback resistor R6 access circuits.

Use as a pre-op amp IC and motivate highly polar, the best to BG2 ~ BG5 quiescent operating current bias mode into resistance from the transistor and the voltage divider composed of regulators, so that there is a greater power supply voltage can be changed under the to maintain almost the same quiescent operating current.

Figure 4 that is, after the improved circuit, BG1 launch junction threshold voltage and BG2, BG3, BG4 the threshold voltage with temperature change, itself, can play a role in temperature compensation. In order to reduce the output of op amp IC quiescent operating current in the output of op amp IC gifts added to the ground side of the shunt resistor R10. With the shunt resistor, the adjustment of BG2 ~ BG5 quiescent operating current can not access the first op-amp IC, directly from one of R7, R8, and R10 divider out the approximate mid-point of reference level. Start with 0 to large adjust R5 so that BG2 ~ BG5 quiescent operating current of 10mA ~ 20mA in between, and then access to op amp IC, the circuit that is able to work properly.

In addition, the output of op amp IC 1 1k current-limiting resistor in series R15, can guarantee the output op amp IC is '0 BG5 will not enter the cut-off state.

Used as a pre-op amp IC and motivate highly polar, the biggest advantage is that the output DC level input signal DC level strict consensus, a difference of not more than 0.05V. This can create OTL power amplifier consisting of two inverted output BTL power amplifier, while in the output DC level and DC level input signal are significant differences between cases, the two OTL power amplifier positive, inverting output DC level tend to be higher than 0.5V, significant effect on the work of speakers equilibrium position. BTL power amplifier positive, RP-output DC level difference between the DC level must be less than 0.1V, trumpet the work of the apparent equilibrium position will not deviate from the free position of equilibrium. Horn's work significantly deviate from the equilibrium position of the free position of equilibrium, the positive and negative direction of the mechanical vibration amplitude asymmetry, issued by the sound waves will produce distorted unnatural.

In addition, the output DC level input signal DC level strict consensus, which makes the use of positive and negative dual power supply OCL power amplifier become a reality. Otherwise, the result of the output DC level and power level of the mid-point difference between the large, will lead to a good speaker does not work properly.

As most of the op amp IC's operating voltage is not high, good performance of high-voltage op amp IC varieties of small, high prices, people can also be used with the same level pre-op amp IC differential amplifier circuit to achieve the same purpose. Figure 5 differential amplification method that is used to do most of the typical pre-circuit than shown in Figure 5 complementary symmetric OTL amplifier basic circuit characteristics of multi-purpose two identical transistors required than shown in Figure 5 improved complementary symmetric multi-purpose OTL amplifier circuits a practical transistor.

Said that they going to, not that people do not know how to design power amplifiers, but by the device of choice constraints, in different historical periods can only use the appropriate design of the circuit. In the 20th century, the late '80s, people began to more easily find properties matching using the same transistor. Due to differential amplification circuit can be extremely quiescent current and accurate design parameters for a given, do not adjust the differential amplifier tubes with a quiescent current. The circuit in Figure 5 the case of the use of 32V power, pre-differential amplifier tubes with a static current of 0.51mA ~ 0.52mA, as long as the first adjust R12 so that BG1 collector to ground terminal of the voltage dropped to 15.4V, and then adjust R5 so that BG2 ~ BG5 quiescent operating current can be between at 10mA ~ 20mA.

BG1 in adjusting the quiescent current, the same they must be adjusted to short-circuit 0 resistor R5 conditions make it BG2 ~ BG5 in a cut-off state, withhold access to the negative feedback resistor R10, with the wire will be BG6, BG0 base short-circuit.

Connected to power, adjust R12 so that the first BG1 collector to ground terminal voltage reduced 15.4V0.2V, and then adjust R5 so that BG2 ~ BG5 the quiescent operating current of 15mA. For insurance purposes, the first R8 and R9 for access into the 100Ω/2W resistors R8 and R9 on the measurement of the static voltage drop should be 1.5V. Disconnect the power supply, measuring adjustable resistor R5 and R12 in which the resistance of the actual value of their fixed resistance into the same resistance. Connected to power, R8 and R9 on the measurement of the static voltage drop should be maintained at between 1.2V ~ 1.8V. Measuring the output level should be the midpoint between the 16V0.3V. Disconnect the power, the BG6, BG0 base Qudiao between the connection wires to the negative feedback resistor R10 access to the circuit. Re-connect power, R8 and R9 on the measurement of the static voltage drop should be maintained at between 1.2V ~ 1.8V. Measuring the output level should be 16V0.2V the mid-point between the difference in charge current magnification the greater the output DC level and signal the smaller the difference between the input DC level. C1 touch with the screwdriver when the input voltage on R8 and R9 dropped significantly larger. And then replace the 0.3Ω resistors R8 and R9, connected to the horn Lyrics. When connected to the power output of the midpoint voltage of the need to rise slowly from zero, which produced only a slight impact on sound. 2 seconds later, the hands touch the C1 input Speaker will issue a "woo" the exchange of sound. The C1 input and ground (negative power supply side) short circuit, speakers should not sound, the actual will be issued by a slight background of white noise or very low voice communication hum.

3. The Improvement of the Power Amplifier Circuit Useful

Bootstrap circuit design using the power amplifier while the circuit is relatively simple, but there is lower frequency cut-off point. The introduction of the bootstrap circuit is in order to avoid when you zoom in on a half-wave there is not enough current available to complement each other to control the use, without lack of transistor used in cases, constant-current source can be used to ensure the right to zoom in on a half-wave when there is sufficient Current available to complement each other to control the use. In the meantime, the differential amplifier is also designed to provide work from the constant current source current, can greatly enhance the suppression of common-mode noise voltage ratio and relax the accuracy requirement.

Figure 6 is to use a typical constant current source power amplifier circuit, in which: BG3 and BG4 constitute a standard constant current source, the former to the front differential amplification to provide extremely 1mA constant total current, 2 only a thin charge of BG1, BG2 be 0.5mA each of the quiescent operating current; which provides a constant current of 2mA, and inspire a very BG5 quiescent operating current of 2mA equal, so that the static Q amplifier output voltage is entirely by the mid-point resistance of the same partial pressure of R13 and R14 set out, are not so large deviation from E / 2. R14 series at the bottom on the D1 is a composite pipe to compensate for the threshold voltage drop above the bottom of a single complementary than the threshold voltage drop across the tube over a PN junction voltage drop, ensuring the same from the resistance voltage divider R13 and R14 determine the midpoint voltage out of more accurate.

Stimulate the quiescent operating current is very BG5 has been on a 1V drop from the R4 and R12 resistance 200Ω identified as 2mA, also do not adjust. Therefore, in the regulation of BG7 ~ BG10 quiescent operating current when the first non-access BG4 and BG5, directly in the R13 and R14 divider out of the mid-point reference voltage and provide 0.4mA ~ 1.1mA of bias current to the BG6 working conditions, Starting from the smallest zero resistance BG7 ~ BG10 adjust R10 so that the quiescent operating current of 15 mA can be. Then replaced by a fixed resistor R10, will BG4 and BG5 access to the circuit board, amplifier immediately work properly. Although the existence of discrete element parameters, which may cause a very real incentive BG5 quiescent operating current and BG4 a small amount of difference between the current source current, differential amplification most will be the output terminal Q of the steady-state voltage deviation from the midpoint of the actual situation of automatically change the static BG1 operating current, so that the actual BG5 quiescent operating current and BG4 constant source current exactly equal. Of course, the actual quiescent operating current BG5 automatically adjusted, the differential amplification extremely quiescent operating current does not allow any one of them significantly reduced too much.

In accordance with Figure 6 in the component parameters, as long as you can make BG5 change 0.1mA quiescent operating current change 1mA, sufficient to achieve the right BG5 quiescent operating current adjustment.

However, due to constant-current source limits the incentive is a very cut-off state can provide maximum current to improve power supply voltage can not be a corresponding increase in the output amplitude. While the corresponding increase in the constant current source current can increase the output amplitude, but to inspire a very quiescent operating current will also increase accordingly, stability deteriorated.

A better approach is to introduce mirror circuit, using the upper and lower symmetrical differential current-mode driver to enlarge the back of the work of complementary symmetry power amplifier tubes. Figure 7 that is used to enlarge the upper and lower symmetrical differential current-mode power amplifier to inspire a very practical circuit, due to higher output power in order to avoid overload damage to the device, circuit added to limit the maximum output current protection. Which, BG4 and BG5 constitute a mirror circuit operating current Ic5 can BG5 and BG4 operating current Ic4 remain completely equal, then the drive BG6.

Achieved by BG6, BG7 constitute the upper and lower symmetrical differential current amplification method. In this way, you can ensure that in the last half-wave signals need to stimulate greater drive current when a very, BG6 also simultaneously be able to export more to the posterior pole of the drive current power amplifier tube. To achieve the same purpose, people can also be taken in parallel and then a pair of complementary symmetrical front differential amplifier, which it has realized BG6 drive. However, the mirror circuit components requirements have not pre-high differential amplifier, using two pairs of differential pre-amplifier and the circuit can not increase any performance, no need to spend the cost of using the kind of awkward. Way to adjust the circuit shown in Figure 6 the use of the same constant current source power amplifier circuit.

From the working principle to consider, using the upper and lower symmetrical differential current amplification methods for the circuit is no longer a very encouraging defects. However, the characteristics of high-power transistors are not ideal, the output current reaches 1A above, the current magnification is only 10 ~ 25, will make driving high-power triode tube complement the work of the above must provide more than 200mA current to the posterior pole.

Complementary control its own power, often exceeding 2W, severe fever, complementary management also need to install another heat-sink. In the electronic component manufacturers have developed to produce high-power Darlington circumstances, the switch has been made within the Darlington composite pipe to make the final stage current amplification tube, we can greatly reduce complementary tube output drive current. Such as the SGS produced TIP series of high-power Darlington, in the output current to 2A above, the current magnification can reach 500 or above, which only need to complement each other with providing 20mA drive current to the posterior pole following the work of complementary tube itself power consumption to below 0.2W.

Need to modify the design parameters only based on the threshold voltage of Darlington transistor threshold voltage is equal to two ordinary times, to provide quiescent bias current shunt resistors R18, R19 doubling of resistance in order to maintain control of the quiescent operating current of complementary does not change. At the same time complementary tube BG9, BG10 base-level voltage drop between the previous increase in the threshold voltage of an ordinary transistor, its quiescent current adjustment circuit means no impact.

As Darlington is not designed for audio power amplifier developed device, the working frequency of the ceiling is not high. Limit the frequency of regular high-power transistor reached only 1MHz, developed specifically for audio power amplifiers to achieve high-power transistor can only 10MHz, preferably no more than 100MHz. Although only the audio range 10Hz ~ 20kHz, but transistor current magnification and the frequency of related, at the upper limit of operating frequency, the current magnification will drop to 1-fold.

This makes the low frequency limit of 20kHz treble amplification transistor capacity than 2kHz Alto amplification of our ability to make low, thus leading to the open-loop state, treble and tenor of the current magnification is no longer remain the same. The closed-loop negative feedback to maintain the same throughout the audio sampling magnification does not change the current mixed-signal inside pitch magnification than the tenor current situation of the low magnification, so that mixed-signal inside the treble actually higher than alto's lower magnification. Therefore, the use of high-frequency high-power transistor limit will enable mixed-signal inside Treble current magnification magnification than the tenor current decline was less.

If you are using only reached the maximum frequency of 1MHz production of high-power transistor audio power amplifier, will feel more than treble 8kHz component is seriously insufficient. Therefore, the foreign manufacturer of electronic components, has been 90 years in the 20th century developed a superior audio performance, dedicated high-power transistor amplifier. Japan 3 3 Ken Ken pipe manufactured by well-known audio power amplifier is the first dedicated high-power transistors, but they are not Darlington require superior performance of the power to do the same before the driver is a very, but also give the driver the front pole of the Power to install heat-sink.

To the 20th century, the late '80s, it developed a higher performance of high-power FET. Any high-power FET operating frequency limit can also be reached 100MHz, but at first the lack of high-voltage high-power FET, manufacturers produce more than 40W power amplifier output power or in selected high-power transistor.

In fact, making use of high-power FET amplifier than the use of high-power transistor amplifier made more convenient. But require special attention to the fact, although the effect of pipe is voltage-controlled device, but the high power FET input gate and the source exists between the large junction capacitance can be achieved around 800P, and therefore the higher the status of the operating frequency to be provided under the same charge and discharge 5mA ~ 10mA drive current.

Channeling Alliance in front of the gate resistance will affect the input junction capacitance charging and discharging, as far as possible to take a small resistance. Figure 11 that is, the practical use of high-power FET amplifier circuit, due to some high-power FET gate voltage there is no built-in limit to protect voltage regulator tube, specially in the circuit by adding a limit-voltage protection voltage regulator tube. With no built-in limit-voltage protection regulator tube high-power FET, welding wire must be used to gate and source short-circuit, welding good power FET and current-limit-voltage protection regulator tube before the gate and the source short-circuit between the wires removed. Use of high-power FET amplifier design, debug mode with the use of high-power transistor amplifier design is identical.

Should be noted that the high-power FET threshold voltage between 2V ~ 3V, (produced by Samsung, the threshold voltage of high-power FET, mostly 2V), the actual high-power FET operating voltage should not exceed the maximum allowable voltage is half the value of the maximum working peak current should not exceed the allowable current of 2 / 3 can only work to ensure safe and reliable.

This requirement is already higher than the three requirements of a wide number of machine control, machine control the actual work of the three voltage can not exceed half the value of the maximum allowable voltage, while the three-machine tube can not exceed the maximum operating current of the maximum allowable peak current of 1 / 3 before being work.

High-power FET has a great advantage is temperature-stable performance is very good, from 25 ℃ ~ 125 ℃, almost exactly the same job characteristics. Therefore, the use of high-power FET, the heat-sink can also be appropriate to allow the temperature as high as 90 ℃, while the transistors are still two of this breakdown may actually allow the temperature of the work should be limited to below 70 ℃.

4. Power Supply "High-Performance" for Power Amplifier

Did not strictly control the output voltage of the midpoint value in requesting an ideal situation, power amplifier can only use a single power supply, the midpoint of the floating power supply with automatic follow ways. Just give a sufficiently large capacity storage capacitors, the actual output capability with the use of dual-power supply there is no difference between OCL output mode.

The reason for using OCL output mode, in addition to surface design a better performance can be further power amplifier, the greater practical significance is the use of positive and negative dual power supply output mode can further reduce OCL circuit background noise. In the pre-power amplifier input stage uses a differential amplifier circuit, the output DC level has been input with the signal DC level remain basically the same, a difference of less than 0.2V. In such a situation, the input signal DC level bias resistor connected to the positive and negative dual power supply potential on the midpoint, you can put a single power supply of the OTL output mode using the positive and negative dual power supply into the OCL Output way, no longer used automatically to follow the mid-point of the floating power supply.

In fact, the use of pre-op amp IC input stage can make the output DC level and signal input DC level remained nearly the same, a difference of less than 0.02V, it is precisely because the internal op amp IC also used to do a differential amplifier input stage , and generally the way of composite pipe to do the input stage differential amplifier circuit, so that flows into or out of IC positive and negative input quiescent current less than 0.1μA, the negative feedback resistor on the static DC voltage drop has been less than 0.01 V.

Identifying characteristics are always matching pipe, composite pipe can be used of course, the way to do input stage differential amplifier circuit, so that the output DC level and signal input DC level remained nearly the same, a difference of less than 0.02V, very consistent characteristic need a pair of tubes made of semiconductor materials, this is the op amp IC production process advantages. In short, the only way to change the OTL output OCL output mode, in the circuit design does not have any increase.

In fact, with work produced in class AB type power amplifier complementary symmetry there is a flaw, which is the last stage high-power amplifier tubes, static current is near the end zone, regardless of the use of high-power three tubes, or the use of high-power FET , in the end zone in the vicinity of the dynamic resistance were significantly higher than the linear dynamic resistance area should be large enough number, the actual can vary by several times to 10 times. Quiescent current is smaller, the greater the dynamic resistance. When the amplifier output voltage is zero when the speaker vibration basin will continue to be damped oscillation to stop. Voice coil moving in a magnetic field generated by currents will hinder the free vibration speaker vibration basin, if the amplifier in series with the voice coil resistance relatively large, it will cause voice coil moving in a magnetic field generated by currents decrease, reducing the role of resistance Nepal, vibration basin Vibration damping is not easy to stop down, the voice of a "dragging its feet" in divergence Shoubu Zhu situation. At the same time, the voice coil woofer speaker moving in a magnetic field induced currents produced by power amplifiers that can not be shorted out as much as possible, it would become alt prevent interference with the work unit loudspeaker drive signals. A better reason why the replay amplifier sound quality, mystery lies in the fact that it has a very low quiescent output impedance.

A power amplifier due to large, fever serious, should not be used under large operating voltage. To do this, you can use the high and low supply two sets of positive and negative manner on the final stage power amplifier tubes with current working status of implementation of the dynamic bias, so that amplifier output voltage amplitude is less than 4V when the high-power amplifier tubes with working in a current class status, the output amplitude is greater than 4V, when transformed to B status. As the rotation of working in the high-power current amplification tube is always in high-current mode of operation, the actual effect is the same way as the work of a purely A.

Figure 10 that is designed using high-power Darlington A high efficiency power amplifier typically dynamic bias circuit, in order to achieve a better dynamic offset, T1, T2 and down two high-power Darlington Complementary tube, in order to increase the threshold voltage bias circuit. Require two complementary parameters governing the same, the actual difference between the current magnification should not exceed 20%.

Dynamic bias is the result of each one and a half-wave output signal through the 4V reference value transform, require dynamic bias changing the speed limit must be more than 20KHz frequency output signal of at least 100 times higher, photoelectric conversion device isolation frequency response to be at least 1MHz, The diodes used must also be high-speed pipe. When the output signal voltage is less than 4V, the optical output transistor is cut-off state, two complementary high-power current amplification tubes were biased in the quiescent current of 1A to work, and when the output signal voltage exceeds 4V, the optical output transistor in the conduction state of two complementary high-power current amplification tube was biased at 10mA quiescent current at work. However, as the output signal voltage exceeds 4V, the current high-power amplifier tubes operating current must exceed 0.5A, 4Ω load must exceed 1A, is also equivalent to the CPI actually work. In the meantime, the output signal when the voltage is 6V or less, BG11, BG12 in the cut-off state, T3, T4 Darlington switch is also closed, T1, T2 two complementary high-power amplifier tubes with current low-voltage power supply from 8V. In the output signal voltage exceeds 6V, when, BG11, BG12 in the conduction state, T3, T4 Darlington switch also turns on, T1, T2 two complementary current amplification tubes replaced by high-power 30V high-voltage power supply, so that High-power current amplification tubes to reduce power consumption.

In the N groove and high-voltage power FET P Erdaogou easy to buy cases, can switch to high power FET to produce high-efficiency power amplifier A dynamic bias. Similarly, T1, T2 and down two high-power FET to be used complementary tube to require two complementary parameters governing the same, the actual difference between the current magnification should not exceed 20%. Bias due to the use of dynamic methods of work, bias circuit to adjust the parameters slightly more complicated.

The specific way the same way as described above, first T1, T2 from the R11, R12 series set out quiescent current regulator out of 1A, then the appropriate allocation of both the actual resistance, so that when the R12 in the short-circuit T1, T2 of the quiescent current 2mA ~ 10mA. That is not completely closed, there is no need to transfer large.

A dynamic bias in view of the main purpose of PA is to reduce the output resistance amplifier itself, in the upper and lower high-power amplifier tubes in the appropriate series current limit protection resistor, the amplifier's maximum output current limit special design in the power part of the change among the circuit.

In this way, matching power amplifier with dynamic offset the use of the CPI level of the two groups also have positive and negative power supply designed to power supply.

Build Speakers ProAc Response 2.5

2009-01-14T20:55:00.009+07:00

Introduction

This is a do-it-yourself (DIY) version of the ProAc Response 2.5, which is one of the most famous speakers in his class of about 1996 to 2003. This model has been replaced by a new model in 2003 called the reaction D25, using different units of the driver, but always in the same way two floostanding concept. 2.5 The answer is regarded as one of the most successful and ProAc known models and is a testament to the skill and expression of its designer ProAc Tyler Stewart. It is perhaps one of the broadest range of 2-way floor conventional speaker cone of his class and is always a good speaker, even by current standards survey. It is a bass reflex design manual "with a good quality, Scan Speak drivers. Drivers used in the draft may not Scan Speak best airline pilots, but it is integrated into a very special way to the best sound possible. The original ProAc Response 2.5 sound is characterized as very musical, soft, consistent, melodic, rich and with a very low bullet proof (for the size). What is missing in May micro dynamics extreme detail in the midrange and treble, it's just because of the tone, even many large and more complex speakers are unable to provide. The draft will ProAc Response 2.5, such as sound or better, depending on your choice of crossing pieces. Try it and you will not be disappointed.

Please note that these sites main purpose is to provide a speaker who is close to the original design in terms of character and expression. After reading this site, you think that can is the only do-it-yourself project to build speaker, because it is well developed and examined. Keep in mind that all the speakers choice of the pros and cons and should be adjusted to your taste, room environment and equipment. There are many other do-it-yourself projects also depends on your situation, some in the links on this website.

Dimensions

Width: 225mm
Height: 1020 mm
Depth: 255mm

Compensation for the large internal volume (2 liters or more) as the addition of large changes weirs.

Approximate weight of the speaker should be completed around 24kg/53lb, but the choice of lightweight materials should not affect the sound.

Port is 140mm long and 75 mm internal diameter and about 350mm high cabinet, and if you like with internal flanges on both ends of the port in the cabinet to reduce air turbulence (use a 100 x 100 mm MDF, which can also brace sided flange or PVC pipe)

50 mm tweeter for high cabinet and outside 35 mm mounted on the side edge (Note: CAO 84mm read error on the side of the cabinet not to 74mm) with 10 mm drivers. 25 mm woofer on the side edges or centered in the middle of the cabinet and 160mm high. Both drivers have been sunk in the case.

Office equipment and stowage: 25mm medium density fibreboard (MDF) for 18 mm and rear side / top and bottom, only 150 mm wide around the port or not.

It seems some models are braced ProAc 2.5, while the other is not and the choice is entirely yours to make. Reports from manufacturers, the two sounds very good. CAO showed brace is placed in the context of the port, in the middle of the cabinet level.

Cabinet coating is 3 to 5 mm or the depreciation of bituminous felt like mass loading, 30 to 50 mm polyester (Dacron 200g/m2 density) stuffing / lining. Siding and depreciation is added to all sides, with the exception of the facade. It is important not to specify or low, so the quantity and density of the coating is used to a balanced voice of the speaker. This may have more effect on the sound as other more expensive and crossing specified components (capacitors and inductors). More companies will lead to unwanted lint-free and forced polling less bass and midrange speakers Express. If you can not find the density or thickness, close to the estimate of the liner.

Cabinet internal volume is 34 liters after the wall of the depreciation is inserted. However, up to 38 liters in volume have been reported in deeper bass extension. Changes in the size of the company for what should be done by increasing the depth and maintain the forward bulkhead of the same size 225mm.

Install base of 25 mm and 20mm thick confluence of all sides on issues, which improves the stability and bass.

Drivers

Tweeters
Scan-Speak D2010/8513-00 19mm (3/4") dome, 150W

Woofers
Scan-Speak 18W/8535-00 and shielded type, Carbon fiber paper, 178mm (7"), 70W

Speaker sensitivity 86dB (1W/m)

Impedance load 8 ohms

The internal cable is Bandridge Superflex OFC LC 7403 which is used in original Proacs. This product appears only to be available in Europe unless ordered internationally.

Crossover

(thanks to Ben Madisound discussion about who has obtained from a friend who saw Audiophile magazine in Hong Kong).

The DCR chokes in ProAc 2.5 is unknown, but the lowest DCR about 0,2-0,4 ohm is recommended for all stimuli.

The original 1996 Stereophile Magazine review and technical evaluation, said the woofer and tweeter are not in phase with each other and with your last tweeter should consider that route. This is illustrated else in the Chinese magazine liaison offices, but it is now proven and unanimously accepted by both listening tests and measures to reduce the polarity of the tweeter circuit linking Hong Kong is correct (see last crossing to the bottom of this page).

The internal cable Bandridge Super Flex LC-OFC 7403. http://www.bandridge.nl/index2.htm

Thank you for Jacq Madisound discussion forum, steps have been made using the standard non-conductive and free 18W/8535-00 custom 18W/S8535-00, which are slightly different physical parameters of ProAc but n 'not affect the sound ( See the Frequently Asked Questions). With the help of the Chinese magazine with drivers produces a mild to moderate 2kHz sound art, which can be reduced by changing the woofer crossover inducer 1.5mH to 1.8mH and cooler 8.5uf to 7uf Jacq and as recommended by the preference of many . Most of the first critical success is based on the original Chinese magazine tweeter connection with reverse polarity. The differences between the crosses are moderate, but important. If the amendment Jacq crossover is still a strong preference of many people know the original sound of the ProAc 2.5 same with that of other changes proposed by Troels G. and others who have much more work in a more neutral clone version 2.5, which is very different-sounding speaker (see his site at the left). If you seek a more neutral tone, or the application of the 9500 Tweeter Scan Speak its recommendations are highly recommended by many.

Parts List

Part	Qty.	Total
Scan-Speak 18W/8535	2	$266
Scan-Speak D2010/8513	2	$104
Cabinets	2	$100-300
3.4 µf capacitor	2	$50-100
4.7 µf capacitor	2
7 uf (8.5 µf Chinese crossover) capacitor	2
47 ohm / 5 W resistor	4
>5-9 ohm / 5 W resistor	2
0.25 mH inductor (air core)	2	$50-100
0.82 or 0.83 mH inductor (air core)	2
1.8mH (1.5 mH Chinese crossover)inductor (air core)	2
Spikes	1 set	$20
Terminal jacks, internal cabling		$50
Total Project Price		US$640-940

Tags: Schematics, Electronic Circuit, Mosfet Amplifier, Audio Amplifier, Active Filter, Basic Knowledge, Basic soldering, Car Audio, Datasheet, Design, Make PCB, Modding, Power Amplifier, Power RF, Pre Amplifier, Power Supply, Loudspeaker

Audio Concepts Titan (12") Powered (250 Watts) Subwoofer Kit

2009-01-08T21:10:00.003+07:00

by Ralph Calabria

(If you would like to have your DIY project published in Secrets, please E-Mail Ralph Calabria at rc@sdinfo.com.)

Introduction

Definition (Webster's Ninth New Collegiate Dictionary):

titan \'tit-en\ n [Gr] 1: cap : any of a family of giants born of Uranus and Gaea and ruling the earth until overthrown by the Olympian gods. 2: one that is gigantic in size or power: one that stands out for greatness of achievement.

If definition #2 is true, the Titan subwoofer should be a real winner. Let's see if the Titan holds up to its name, or is it merely a Greek myth?!

Now I know a lot of you are saying, "Oh no, not another subwoofer project! Can't we have a little variety?" OK, I admit it. BUT, this project has some major differences in its design compared to previous ones. The most important difference is that it is a powered sub, which means it has its own amplification system and active crossover. Besides, one of the biggest and most noticeable improvements one can make to an existing setup is adding a good powered subwoofer. Since this sub can be purchased as a kit, this article is intended to do double duty as a DIY project and a kit review. If you haven't gotten the speaker building bug yet, or you're still contemplating but haven't taken "the plunge", this just may be the project to get your feet wet. Building this puppy is super easy and fun!

Who is Audio Concepts (ACI)? There are probably some folks out there who have never heard of them. That may be because they are a company that deals directly with the consumer. No middle man. No distributor. No sales person. Their advertising campaigns are not as "in-your-face" as some of the larger companies. "Dealing Direct" has become vogue of late, but ACI has been doing it for over 20 years. Founded by Dr. Mike Dzurko, the company has evolved from a one-man show to a very successful business that works out of a renovated nineteenth century church. The company's forte is providing high quality loudspeaker systems at a reasonable price. By avoiding the layers of profit-takers, ACI can pass some of the savings to their consumers.

Design considerations

I was looking for a sub that pretty much did it all: response to 20 - 25 Hz -3db with substantial output, flexibility to ensure a seamless blend between the sub and my existing main speakers, an attractive looking design that could double as speaker stands (should I decide to get stereo subs), all in an enclosure that wouldn't take up half the free space in my home theater room. I don't think that's asking too much! Do you?

I first looked into designing a sub from scratch. Among the many DIY drivers I considered, the ones I found on ACI's home page caught my eye, in particular the ACI 12E and the ACI DV12 (both 12" drivers). They offer several alignments for their drivers in both sealed and vented configurations. I checked them out with my MacSpeakerz box design program and confirmed ACI's alignments. However, to get even 25 Hz flat out of these drivers, I would have to build a cabinet with about 5 ft³

internal volume. That translates into one massive, heavy box! Considering these designs, I would still have to come up with an active crossover to provide the flexibility I wanted, plus a power amplifier to driver the speaker. Although my home theater room can use a couple of new end tables, I decided that these monsters would just be too big for what I envisioned.

I've known about the Titan for a couple of years now, and I was aware of the good reviews the Titan (and other ACI products) have received over the years. I decided to look at the Titan a little more closely to see if it was a match for my design criteria. As fate would have it, the Titan was just what I was looking for in terms of power, flexibility, size, extension, and output.

The Titan comes in two forms. There's the just-plug-it-in-and-off-you-go form, which sells for $799, and there's the Do-It-Yourself form, which is a kit that comes with just about everything you need except the cabinet. The kit sells for $529, but it is currently priced (for a while) at $499 (including free shipping). If budget is your concern, and you are handy with tools, you won't find a better deal than this, considering it has a 12" driver and 250 watt amplifier.

After speaking with my friend Leo, and asking him if we could cut some MDF at his dad's house, he asked me what I was building this time. When I told him it was a powered sub, he wanted in on the action. So, I offered to help him build one. I did have an ulterior motive, however. I was looking to check out stereo Titans. After getting his OK to borrow his Titan for the evaluation when it was finished, we were set to go.

The Titan design

The Titan was designed to operate in a relatively small sealed cabinet (1.9 ft³ internal volume; Q = 0.6). At this box volume and a standard closed-box Q of 0.707, the ACI 12E will stay flat to about 40 Hz, then drop off at 12 db/octave below 40 Hz (meaning -12 dB at 20 Hz). So how does a speaker like the 12E, designed to go flat to 40 Hz at this box size, extend its useful range to about 20 Hz? This is done by inserting an electronic circuit before the amplification of the signal that boosts the frequencies at the point where they start dropping off (at 12 dB/octave). This is called equalization (EQ). To accomplish this, particularly at these low frequencies, takes quite a bit of amplification ability. Not just any system can be EQ'd. The driver also has to be able to handle everything that's being thrown at it. A motion accelerometer sensor is sometimes added to protect the driver from distorting or blowing up. This type of approach, commonly known as active-servo control, performs as a feedback controller by limiting the output the driver sees as driver limitations are approached. Several powered subwoofers on the market use this technology. For the Titan, the woofer is put in the output loop of the amplifier. This is how ACI gets the Q of 0.6 and extends the response to about 20 Hz. The Titan uses a high-pass crossover filter that is controlled at 20 Hz with an 18 db/octave slope. When the driver/amp limitations are approached, the frequency of the filter increases. The downside is the Titan won't be permitted to play tones much below 20 Hz at any appreciable volume. The nice thing about the Titan design is that the upper frequency limit does not change, and constant output is maintained. For example, if you have the Titan's crossover set at 70 Hz, and the frequency limiter is activated, frequencies that are between the set limiter and 70 Hz are not affected with regard to output. This approach maintains the seamless blend (crossover point) you've set for your mains and sub.

The Titan comes with a 250 watt rms amp specified at 0.1% THD. The amp has a massive toroidal transformer, bipolar output devices, and computer grade power supply capacitors with selected film caps in the signal path. A temperature switch monitors the output devices of the amp. If the amp overheats, the system shuts down to protect the circuits. Once the heat sinks cool, power is restored.

Aside from the current-sensing feedback circuitry, the Titan comes with an active crossover that allows you to select any low pass crossover frequency from 50 Hz to 180 Hz. The filter starts at 12 dB/octave and increases to 24 dB/octave. There is also a phase switch that allows you to set the sub at 0° or 180°. Most manufacturers provide speaker-level inputs and outputs on their subs so the amplified signal coming from the receiver/amp is sent to the speaker-level inputs of the sub, then routed through a high-pass filter, and on to the satellite speakers by way of the speaker-level outputs on the sub. The Titan does NOT have speaker-level inputs/outputs. It does come with three speaker-level adapters. These adapters essentially convert a speaker-level output coming from a receiver to a line level output. This line level output is then hooked up to one of the three Titan line-level inputs. If you have a line-level sub output on your receiver/preamp, you don't need to use the adapters. If you're looking to limit the frequencies your satellite speakers see, ACI sells a high-pass filter (~85-90 Hz; 1st order slope). For a detailed description (including photos) of the many ways to hook up a Titan to your system, check out ACI's home page at http://www.audioc.com/diy/kits/titank.htm.

The Titan kit

The following hardware is included with the Titan kit:

1 - 12" long-throw polypropylene woofer (ACI 12E)
1 - 250 watt rms amplifier module with variable active crossover
3 - speaker-level to line-level adapters
2 - speaker terminal connectors
Closed-cell adhesive-backed foam
Acoustical polyester stuffing
Instruction/owner's manual

The following hardware is NOT included with the Titan kit:

Wood to build the cabinet
Cabinet finishing materials
Screws to secure the woofer and amplifier
Speaker spikes (points)

The kit came tightly packaged in one box. The amplifier/crossover module comes completely assembled, so there's no need to solder anything. The manual includes some frequently-asked questions (and their answers) regarding building DIY speaker projects as well as some other useful information regarding setup and placement of the sub. The actual assembly-process part of the manual was a little thin. Although most of the diagrams were just fine, some of the cabinet diagrams were a bit confusing. I thought there could have been additional assembly instructions to better help the newbie on the block. The cabinet diagram also states that the circle cutout measurements for the driver and cabinet base top are a radius cut, when it should be stated as a diameter measurement. Anyone with some common sense, however, could figure out that an 11 1/4" radius circle (implying 22 1/2" diameter) won't fit in a cabinet that's 13 1/2" wide! The descriptions of the braces were not fully described as well. For example, the internal brace diagram shows a brace 2" wide for all sides. This is fine for the upper brace. However, there is no indication that the lower brace should be cut to accommodate the amplifier hole in the back. Again, common sense prevails here, and the drawing of the cabinet with a portion of the wall cut out for internal display purposes DOES show the brace cut, but you really have to look. A quick and simple update of the drawings would probably eliminate a lot of phone calls to ACI for clarification. I had no problem figuring out the internal dimensions from the plans, but perhaps it would be helpful if there was a list of board dimensions, a quantity of each size, and what the boards are used for, something on the order of the diagrams I've included for my enclosure. This would make the construction process a little less confusing. Everything I've mentioned here never presented a problem in the construction process. Most of the suggestions I've made are based on how I personally prefer cabinet plans to be laid out. During the initial part of the design layout, I had some questions about the plans, and Mike and Joe at ACI were very helpful and receptive in this area.

The cabinet

ACI cabinet plans

The Titan cabinet has an internal volume of approximately 1.9 ft³ and measures externally 13.5"W x 14.5"D x 26.5"H. The height includes the cabinet base, which is screwed onto the bottom of the cabinet. The driver is configured in a down-firing position. The design incorporates four braces; two "mini" braces and two square cutout braces. All walls and braces are constructed of 0.75" MDF. The cabinet base is constructed of 1" MDF, and is assembled separately from the cabinet. There are 4 - 1" diameter x 1 3/8" H dowels that are sandwiched between the top and bottom of the cabinet base. For a more detailed description of the cabinet drawings, go to ACI's website listed above.

Modified cabinet plans

Here are the cabinet plans I used for my sub:

The overall height of the Titan cabinet was a little too tall to double for a speaker stand. My main speakers need to be at a height of approximately 22" - 24" off the floor in order for the tweeter to be at ear level when seated in the primary listening position. In order to bring the overall height of the cabinet down a bit, I had to change the dimensions. When it comes to building speaker cabinets, I've always lived the philosophy of "build it as strong as you can without needing more than three people to move it". Considering I would potentially use the sub(s) as a speaker stand, I didn't want my mains vibrating off the sub. I decided to use 1" MDF for the walls, braces, and cabinet base. Using 1" MDF increases the stiffness of the cabinet by a factor of 2.4. (Stiffness is proportional to the wall thickness cubed. A 1" wall is 1.3333 times thicker than a 0.75" wall. So, 1.33 X 1.33 X 1.33 = 2.4.) I also modified the bracing somewhat. The two top braces where changed from 2" wide to 1.5" wide. Because the cabinet was made shorter, everything inside was compressed. So, in order to leave at least 3" between the shelf brace and the top braces, I shortened them by 1/2". The middle brace was changed to a shelf brace (see cabinet drawing for details). The bottom brace was left unchanged. However, an additional 1 1/2" wide brace was added which sits on top of the bottom brace across the width of the cabinet. This was an afterthought. When the cabinet was assembled with the exception of the front panel, I whipped out my high-accuracy cabinet-stiffness testing apparatus, a.k.a., the knuckle of my right middle finger. Striking the knuckle at various intercepts on the cabinet, and using a constant linear velocity of 15.24 cm/second equidistant from the cabinet, I determined that the lower brace needed some "beefing up". Because the lower brace is cut to accommodate the amp, a shelf brace was not possible. So, I guess you can call it a half-shelf brace. There's a big difference in the "stiffness test" at the middle shelf brace compared to the lower brace. The "pitch" of the cabinet is much higher at the shelf brace (higher is better). Adding the extra bracing helped raise the pitch of the cabinet at the lower brace.

The original plans call for making the cabinet base as a separate unit. Although the bottom of the cabinet base and the dowels are separate from the main cabinet in my design, I decided to make the top of the cabinet base a "permanent fixture" of the main cabinet. Why? Gluing and screwing the top of the cabinet base to the main cabinet strengthens the baffle. Also, by making the top of the cabinet base part of the cabinet, I got the cosmetic look I was going for in a veneered piece rather than a painted piece. Did I HAVE to make all these changes? Of course not. The original cabinet design is more than adequate (and attractive too). However, if you can, and it if works for your design goals, why not?! This decision was driven mostly by cosmetics. (NOTE: Just keep in mind that if you change the dimensions of the original plans, make sure the internal volume stays at 1.9 ft³ ± 5%, after accounting for bracing). The overall sound of the sub shouldn't change. Making this alteration will, however, make it more difficult, but not impossible, to remove the driver. The driver is 12 1/4" in diameter, and so is the hole in the upper cabinet base. I don't plan on removing the driver very often (hopefully never!), so I didn't consider this a major pain.

Assembling the cabinet

After building my Audax A652s (DIY #1), I 'd say that building this sub was a cake walk. I could easily recommend this kit to anyone who has never built a speaker project before, provided they have some woodworking know how (or know someone who does), a lot of common sense (or know someone who does), and access to some power tools. Many of the techniques I used in making the A652s were also used in making the Titan.

After cutting all the panels with a table saw, I used a jigsaw to cut the holes for the amp and the braces. I used a router with a circle cutting jig to cut out the holes for the driver and the top of the cabinet base. I assembled the back and the two sides first, using the glue-and-screw technique. I would recommend getting a couple of 90° clamps for this part of the assembly. The pieces are first dry fitted and aligned using these clamps, then one piece is raised up to apply the glue, the boards are clamped together again and then screwed using #6 1 5/8" drywall screws (don't forget to coutersink). Once the pieces are screwed, the clamps may be removed and used for the next pieces to be assembled. These braces really are worth their weight in chocolate. It makes this part of the construction a one-person job.

Once the back and sides were assembled, I installed all the braces and the baffle. To keep everything in place while screwing in the pieces, I used three Eagle Bar clamps with a 30" extension; one to pull the sides in and two to pull the brace down into the back of the cabinet. These clamps did a great job at keeping everything snug and in place while I drilled the pilot holes for the screws. The small 1.5" braces were held in place by two bar clamps until glued and screwed in place. Keep in mind that in the cabinet diagram, the positioning of the braces is determined by the FREE-SPACE distance from the bottom of the cabinet. If you want to measure from the bottom of the cabinet, add 1", which is essentially the thickness of the baffle. The shelf brace should start approximately 1/2 inch above the amp cutout.

I then installed the top and the cabinet base top. I didn't need to flush mount the driver in this case. No one's going to see the down-firing driver, so cosmetically it's not a concern. I sealed all the outside joints of the cabinet with Silicone II, then put the front on and sealed that as well. Once the cabinet was assembled, I filled all the countersink holes with wood filler. When the wood filler was dry, I sanded the entire cabinet using a random orbital sander. I sanded all the butt ends until they were flush with each other. I routed the two front edges of the enclosure using a router and a 1/2" roundover bit. The bottom of the cabinet was then spray painted using a semi-flat black enamel.

Cabinet finishing

Cabinet finishing is always up to the end-user. There are many ways to finish a cabinet. Painting, rugging (there's just no accounting for taste!), veneering, and laminating are just a few of the more common finishing processes used. I love the look of real wood. Since I can't make my cabinets out of real hardwood (there are many reasons why you shouldn't build your speaker cabinets out of solid hardwood), the next best thing is to use real hardwood veneer to cover the MDF cabinet. I chose a 10 mil paper-backed red oak veneer to match my A652s. There are a few ways to apply veneer to MDF. The most common are using varying types of contact cement, wood glue using clamps or vacuum presses, hide glue, and dried wood glue. I decided to use what worked for me on the last project, the dried wood glue and hot iron technique. The last time I tried this technique, I applied the glue to both the cabinet and the veneer in somewhat liberal proportions. The glue, being a water-based product, took on the order of several hours to dry. This time I applied a thinner coat of glue to both the veneer and the substrate. As the glue dried, I checked for any areas that weren't shiny (an indication that the glue soaked into the MDF/veneer). I applied another thin coat of glue, not waiting for the first coat to dry. Even though I used two thin coats of glue, it only took about 1 1/2 hours for all the water to evaporate. It's important to make sure that all the water is gone. If water is still present in the glue, it will boil when the iron is applied, and the veneer will bubble. To accelerate the drying process, I applied the glue in a warm, dry room and used a space heater to get it nice and toasty. Working with the dried glue immediately after the water has evaporated really helped melt the glue more easily and enabled the bond to take place quickly. This resulted in no bubbling or scorching of the veneer. For a detailed description of this technique, check out the Audax A652 project (DIY #1) at http://www.sdinfo.com/volume_3_3/v3n3d.html. As each piece was bonded, I used a veneer trimming bit on my router to shave the excess off the edges. Preparation of the veneer for staining was done as in DIY#1.

The stain was the same pickling oak stain in order to match my mains, and the topcoat was semi-gloss polyurethane. For a detailed description of the finishing procedure, once again I refer you to DIY #1 at the above URL.

Installing the driver, amp, and stuffing

The last chapter in the assembly process is putting in the stuffing (damping material), attaching the wires from the amp to the speaker, and installing the speaker and amp module. Before applying the stuffing, I vacuumed out any sawdust that had fallen in, then used a spray adhesive to keep the stuffing in place in the cabinet. The stuffing comes in a sheet that is about 2' x 4' x 3/4". I "poofed" it up and made sure the stuffing material was not too close to the driver. I allowed some space for the driver to breathe and the cone to move freely. The extra brace piece on the lower brace helped keep the stuffing from falling down onto the driver. (NOTE: If you use spray adhesive, wait until the fumes from the spray adhesive have completely evaporated before moving on.)

I then applied the foam gasket material to both the driver and amp. The kit does not come with the hardware to install the amp and driver, so you're on your own here. (I can see not including screws for the driver, as some DIYers prefer to use T-nuts or some other method. The amp, however, has six holes used to screw it into the cabinet. I would like to have seen hardware provided here to eliminate the guess work with regard to the length, head size, etc.) I installed the amp first, then the driver. For the amp I used #6 3/4" black pan head particle board screws, and for the driver I used 1 1/2" black pan head screws. The driver screws were a wee bit long for the job, but the head on them was a perfect fit for the driver (and I had them in surplus :-). The kit comes with speaker terminal clips that make the amp-to-speaker connections easier. This requires crimping one end to the amp wire and crimping the other end to the speaker terminal, red to positive and black to negative. No soldering is necessary.

Cabinet Base

As I described earlier, the top of the cabinet base was integrated with the main cabinet. The bottom of the cabinet base was routed on all four sides using a 3/8" beading bit to make it look like molding edge. The dowels were cut 1 3/8" long using a miter saw. I used a slightly fatter dowel (1 1/4") than the original design because my cabinet is wider and heavier. The dowels were stained with the pickling oak stain and top coated with semi-gloss polyurethane.

A hole was drilled through the center of the dowel. The dowels were then positioned 1 1/2" from each adjacent side of the cabinet base bottom, and a hole was drilled into the cabinet base bottom through the hole in the dowel. The hole was made just large enough to allow a #10 4" drywall screw to pass through with a little resistance. I aligned the cabinet base bottom with the main cabinet bottom and drilled a pilot hole in the main cabinet. The top and bottom of the cabinet base were then spray painted gloss black. The holes in the cabinet base bottom, dowels and cabinet were aligned, and the drywall screws were used to attach the base.

After everything was together, I installed a set of speaker spikes on the bottom of the base. I used a set of ACI extra points, which are not included with the kit.

It's break-in time!

Audio Concept really stresses the need to break in the Titan for at least 40-60 hours. That's a lot of bass notes! They claim it is necessary to stretch out the driver surround. Before doing any serious listening, I played some bass-kicking CDs. I tried to do most of the break in when everyone was fast asleep or when no one was at home (when trying to break in a wall-shaker like this sub, you don't WANT to be home when pictures start falling all around you)! I listened to the Titan for a while with no break in time, and then again at various stages of the break in. The Titan behaved like a fine scotch, getting better with age. It also got louder with time during the break in (just ask my wife at 3:00 a.m.) Based on my experience, I would suggest a minimum of 40 hours before really trying to evaluate the performance of this sub. You'll be duly rewarded!

Days of thunder

I first went about finding the best place in my room to plop down the sub (Position #1 described below). After finding the right crossover point, I was able to provide a seamless blend between my mains and the Titan. The Titan was primarily designed for music reproduction, and I'd say up front that it did an excellent job at this. The first thing that jumped out about this sub was the tightness of the bass. With a system Q of 0.6 in a sealed enclosure, this was not surprising. The sub also had excellent transient response. This was made apparent when listening to the timpani in "Farefare for the Common Man" (Aaron Copland - Telarc). The Titan's sealed enclosure provided very controlled bass. No matter how loudly I played the Titan, there was no audible sign of distortion. This was expected because of the Titan's feedback loop controller, but all the same, its electronic devices worked quite well. After playing track after track of bass-enriched CDs, the Titan continued to impress me with its solid, clean, tight bass, all at ample output. I can't stress enough how musical this sub sounds.

So, what about movies? It's hard to find a sub that can deliver both a satisfying music AND movie experience. There's no question as to the Titan delivering the goods for musical reproduction. However, a sub has to produce a fair amount of tactile effects to be convincing in movie soundtrack reproduction. The way my room is situated, some compromises needed to be addressed. In the position where the Titan exhibited the smoothest response and produced "delocalized" bass (Position #1; between my mains), the sub's tactile effect was reduced. In the position where the greatest tactile effect was produced (Position #2; off to the right of my right main, close to my couch), there was definite localization of the bass, which was very distracting, particularly when watching movies. I found this phenomenon to be attributed to the floor in my home theater room and not the subwoofer. My floor is concrete, covered with hardwood planks, and then by carpet. Very hard, and very dead! Although I couldn't really feel the bass in position #1, the walls vibrated enough to rattle clocks and pictures. However, there was a totally different experience going on upstairs. My living room floor directly above my home theater room almost reached its resonance frequency! My daughter, watching TV upstairs, almost lost her glass of milk, which she had placed on the floor. In position #2, I could feel the bass more (my body vibrating) because the sub was close to my couch, and the vibrations were transferred to me through the couch.

I selected some bass-intensive scenes from the "Star Wars Trilogy Special Edition", Disney's "Aladdin", "The Lost World: Jurassic Park", "The Fifth Element", "Contact", and "Twister" to put the Titan to the movie test. Although the Titan was designed to be more of a musical sub, it did a fine job reproducing movie special effects such as explosions, rocket engines, claps of thunder, and associated rumbles. The Titan didn't flinch, no matter how loudly I played it. My ears gave out well before the Titan did. However, the Titan will only play as loudly as the limit controller will allow, starting by slowly cutting off the lowest octave first and working its way up the frequency scale. As I continually cranked it up, I sensed no discontinuity in the balance of my system, indicating that the output of the upper frequencies close to the crossover point of the sub and mains was not interrupted.

Associated equipment for this evaluation included:

B&K AVP2000 preamp
B&K AV5000 power amp
Pioneer CLD-D703 combi player (modified for AC-3)
Marantz DP-870 Dolby Digital Processor
DIY Audax A652 mains
Paradigm CC-300 center speaker
Paradigm ADP-150 surrounds
Audioquest Quartz and Indigo cables

Are two thumpers REALLY better than one?

As I mentioned before, my friend Leo was nice enough to lend me his Titan for the stereo sub evaluation. For this test, I replaced my speaker stands with the subs and put my mains on top. I separated the mains from the subs using four high-density foam pads at each corner of the mains.

Using two subs will give you the flexibility of keeping the subs' crossover point slightly higher (if your setup calls for it), as bass delocalization is less of a concern. Using two subs also increases output by about 6 dB (but there can be cancellation at some frequencies, so placement is critical).

Using two Titans produced a smoother, more balanced in-room response when I compared the same music tracks using a single sub. The overall sound improvement was very noticeable on movie playback as well. As I mentioned before, my room effects contributed to or took away from the tactile effect of the sub. However, with two subs, the overall effect with movies was astounding, with great balanced, centralized sound, AND phenomenal special effects. Two subs with this much output extending down this low is almost suicidal!

Cost estimate

Here is a breakdown of the overall cost of the project. I had a lot of the hardware materials left over from my last project. I didn't include them in the price. However, I did give a unit cost so these may be added should one not have these materials around. Since materials cost varies from region to region, your cost may differ somewhat.

TITAN KIT: ACI
1- ACI 12E 12" polypropylene cone driver - - -
1- 250 watt amplifier module - - -
Acoustical polyester fill - - -
Foam gasket material - - -
3- Speaker level adapters - - -
Kit Cost: $499.00

Building Materials:

Material

How Much

Price

Source

1" Medium Density Fiberboard	25 ft2 at $0.96/ft2	$24.00	Lumber Yard
1 1/4" Hardwood Dowels	0.5 Foot at $1.00/Foot	$0.50	Home Depot
Carpenter's Wood Glue	1 Bottle at $5.49/Bottle	$5.49	Home Depot
Silicone II Sealant	1 Tube at $2.97/Tube	$2.79	Home Depot
#6 1 5/8" Drywall Screws	Handful at $2.30/Pound	$2.30	Home Depot
Black Anodized Screws	14 at $2.50 for 50	$2.50	Home Depot
Red Oak Veneer (paper backed)	16 Feet2 at $1.30 Foot2	$20.80	Lumber Yard
Pickling Stain	1 Quart MinWax at $5.69/Quart	$5.69	Home Depot
Gloss Polyurethane	1 Quart MinWax at $8.49/Quart	$8.49	Home Depot
Speaker Spikes	1 Set of 4 at $15.00/Set ACI	$15.00	ACI
Black Spray Paint	2 Cans at $1.59/Can Krylon	$3.18	Home Depot
Wood Filler	1 Can at $4.89/Can	$4.89	Home Depot

Materials Cost: $71.42 (estimated from using only part of the tubes and bottles)

Grand Total: $570.42

For the most part, people like to save money. By doing it yourself, you're doing just that. The total cost of this project was about $570. Buying a Titan pre-assembled would cost $799. So, you're saving about $230 by building your own cabinet. You get the added advantage of building it to suit your needs (size, strength, shape, cosmetics, etc.), and you get the satisfaction of knowing you did it yourself. Although building this cabinet was pretty easy, it's also important to know that using the right tools and techniques will help your chances to succeed. Should you decide to build the cabinet yourself, and find that it's not turning out quite the way you expected, fear not. ACI sells the Titan cabinet as a stand-alone item. All you would need to do is install the hardware. You won't save any money, but your investment in the kit is not lost.

Final remarks

If you're looking for a sub that will reproduce audio soundtracks with tight, detailed, natural bass, you may have to search long and hard for a better sub than the Titan. Can you buy (make) a sub that will produce higher output levels and extend lower than the Titan? Yes. But I think the question you should be asking yourself is do I NEED a sub that will produce higher output levels and extend lower than the Titan? That answer really depends on your requirements (desires) and the amount of cash you have burning a hole in your pocket. After listening to the Titan for a while, I have to admit that even at $799 straight from the factory, the Titan is quite a deal. This attractive looking sub (which also makes for a very attractive speaker stand) certainly performs and looks like a more expensive component. I have heard subs costing twice the price, and looking half as nice, and the Titan stays very competitive. If you've got the funds to support two Titans, even better! Your subwoofer needs will be satisfied for many years to come, all at a mere DIY price of about a kilobuck. I do have one problem, however. How am I going to tell Leo that he's not getting his Titan back!

Factory direct, the Titan is available in three finishes: clear lacquer oak, clear lacquer cherry, and black stained oak. Other special-order finishes are available by request.

The Titan certainly lives up to its name. Thank you, Mr. Webster, for summing it all up for us!

Special limited-time offer

ACI will be holding a special limited-time offer to readers of Secrets of Home Theater and High Fidelity. If you order the Titan kit and mention this Secrets article, ACI will include a set of Extra Points speaker spikes at no additional charge.

Acknowledgements

I'd like to thank Leo and his dad for helping me cut the wood on their table saw, and to Leo for lending me his Titan for the stereo sub evaluation. Thanks also go out to Mike Dzurko for all his help during the Q&A (pre-construction) portion of this project and for making such a nice powered subwoofer kit available to DIYers.

Ralph Calabria

MP3 Car Audio Power Amplifier

2009-01-08T01:53:00.004+07:00

Here, it is a diagram of an Car Audio active loudspeaker. The LF353 of, National Semiconductor. For Best Results using NE5532 , is going to split audio signal into three bands (Active Filter). SANYO'S LA47536 is going to amplify these signals. In stereo mode, we shall have the action of eight high speakers who are going to create a very important sound pressure.

Three Band Active Tone Control (Active Filter):

Description :
LF353 Wide Bandwidth Dual JFET Input Operational Amplifier
General Description:

These devices are low cost, high speed, dual JFET input operational amplifiers with an internally trimmed input offset voltage (BI-FET II technology). They require low supply current yet maintain a large gain band width product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents. The LF353 is pin compatible with the standard LM1558 allowing designers to immediately upgrade e the overall performance of existing LM1558 and LM358 designs. These amplifiers may be used in applications such as high speed integrators, fast D/A converters, sample and hold circuits and many other circuits requiring low input offset voltage, low input bias current, high input impedance, high slew rate and wide bandwidth. The devices also exhibit low noise and offset voltage drift. (National Semiconductor)

I recommended using IC NE5532.The NE5532 is a dual high-performance low noise operational amplifier. Compared to most of the standard operational amplifiers, such as the LM1458, LM1558, or LM4558 it shows better noise performance, improved output drive capability and considerably higher small-signal and power bandwidths. This makes the device especially suitable for application in high quality and professional audio equipment, instrumentation and control circuits, and telephone channel amplifiers. The op amp is internally compensated for gains equal to one. If very low noise is of prime importance, it is recommended that the NE5532A version be used which has guaranteed noise voltage specifications.

Features : Internally trimmed offset voltage: 10 mV Low input bias current: 50pA Low input noise voltage: 25 nV Low input noise current: 0.01 pA Wide gain bandwidth: 4 MHz High slew rate: 13 V/us Low supply current: 3.6 m High input impedance: 1012. Low total harmonic distortion : <>

Power Amplifier :

When the Power amplifier is installed behind in the suitcase, we shall need a switch works stop. The LA47536 possesses a function stand by in it pin4. This pine require a small tension superior to 2V in start up the amplifier. Transistor Q1 and Q2 makes the function of walking stop for distance. When the driver activates the left indicator, either light the back fires or press on the brake , lamps rear ignite driving Q2 who he even made to drive Q1 who applies a tension > 2V on it pin4. Overview

LA47536 Four-Channel 45 W BTL Car Audio Power Amplifier

The LA47536 is a 4-channel BTL power amplifier IC developed for use in car audio systems. The output stage features

- A pure complimentary structure that uses V-PNP transistors on the high side and NPN transistors on the low side to provide high power and superb audio quality.

- The LA47536 includes almost all the functions required for car audio use, including a standby switch, a muting function, and each protection circuit. It also provides a self-diagnosis function (output offset detection). (Sanyo)

Functional Description
1. Standby Switch Function (pin 4)

The pin 4 threshold voltage is set to be 2 VBE. When Vst is 2.0V or higher, the amplifier will be on, and when Vst, is 0.7V or lower, the amplifier will be off. Note that pin 4 requires an operating current of at least 40uA.

2. Muting Function

The IC is set to the muted state by setting pin 22 to the ground potential. In this state, the audio output is muted. The time constant with which the muting function operates is set by an external RC circuit, and this time constant influences the pop noise that occurs when the amplifier is turned on or off.

The muting on and off times due to the recommended external component values (R=10k, C=3.3uF) are as follows.

Muting on time: 50ms
Muting off time: 20ms

3. Self-Diagnosis Function (Speaker burnout prevention)

During steady state operation, the LA47536 detects, internally, whether or not an abnormal amplifier output offset has occurred, and outputs this signal from pin 25. Applications can prevent speaker burnout and other problems by having the system microcontroller detect this pin 25 output signal and control either the standby state or the power supply. (An abnormal output offset may be caused by, for example, input capacitor leakage current.) The pin 25 signal is turned off by setting pin 1 to the ground potential.

4. Oscillator Stability

In some cases, parasitic oscillations may be induced by the PCB layout. This oscillation can be eliminated by adding the components listed below. Note that the optimal capacitor value must be verified by testing in the actual mounted state in the end product. Connect a capacitor and resistor (0.1uF and 2.2) in series between each output pin and ground.

5. Audio Quality (Low band)

The frequency characteristics in the low frequencies can be improved by making the capacitance of the input capacitors variable. The recommended capacitance is 2.2uF and smaller.

6. Protection Circuits

Do not ground the outputs with the STBY voltage at around 1.4V. Also, do not turn the IC off in the grounded state with a time constant provided for the STBY voltage.

7. Pop Noise

Although the LA47536 includes an pop noise prevention circuit, pop noise can be reduced even further by using the muting function as well. Activate the muting function at the same time as power is applied. Then, after the output DC potential has stabilized, turn off the muting function. When turning the amplifier off, first turn on the muting function and then turn off the power supply. These two methods are effective at minimizing pop noise.

Printed Circuit Boards :

Source: http://www.zen22142.zen.co.uk/Circuits/Audio/150wmp3.htm

50 Watts Simple Audio Power Amplifier from OSU IEEE Student Group

2009-01-07T19:42:00.003+07:00

This simple audio power amplifier was originally designed for a circuit board workshop, conducted by the OSU IEEE Student Group. At the workshop, 20 participants each constructed this amplifier, by etching and drilling the single sided circuit board, soldering all components, and attaching a pre-built heatsink assembly with the output transistors. Three workshops were held between 1995 to 1996. Though the design is simple, these amplifers have impressive preformance, with a frequency response to approx 40 kHz, very low noise, reasonably fast slew rate, and approx 50 watts (true "RMS" power) with the proper +/- 40 volt unregulated power supply.

Someday, I'll do some substantial testing to determine exactly what the power output is, and create some more detailed pages about how to build this amplifier.

Update: the input transistor are 2N5210, not 2N2510 as shown above

Transistor	Color
2N5210	Blue
MPSA56	Pink
MPSA06	Yellow
2N3904	Green
2N3906	White

These color parts placement diagrams are also available in as postscript files in a ZIP archive.

This parts list is under construction... I'm gathering part info for several lists, so pleast don't assume this list is totally correct or complete.

Qty	Vendor	Part #	Description
1	Newark	58F508	Wakefield 421k Heatsink
2	Mouser	567-7-373-BA	Low-Power TO-220 heatsink
3	Mouser	592-2N5210	Low Noise NPN, TO-92
1	Mouser	161-4215	Phono Jack, 90 deg PCB mount
1	Mouser	592-MPSA06	Medium Power NPN, TO-92
1	Mouser	592-MPSA56	Medium Power PNP, TO-92
1	Mouser	511-TIP29C	Power NPN, TO-220
1	Mouser	511-TIP30C	Power PNP, TO-220
1	Mouser	511-TIP33C	High Power NPN, TO-218
1	Mouser	511-TIP34C	High Power PNP, TO-218
2	??	2N3904	General Purpose NPN
1	??	2N3906	General Purpose PNP
2	Mouser	583-1N4742A	12V Zener Diode
5	Mouser	592-1N4148	Small Signal Diode
3	Mouser	583-1N4001	1A (slow) rectifier diode
6	Mouser	140-XLR16V100	16V 100uF Capacitor (radial)
1	Mouser	140-CD50N6-331K	330pF NPO Capacitor
1	Mouser	141-100N5-051J	51 pF NPO Capacitor
6	Mouser	140-PF2A104K	0.1uF Mylar film capacitor
2	Mouser	28PR002-0.3	3 Watt 0.3 Ohm Power resistor
1	Mouser	594-63P502	5K Top adjust cermet trim pot
2	Mouser	29SJ500-2.2K	2.2K 1/2 Watt Carbon Resistor
1/2	Injectorall	PC18P	4x6 board
5			1/2 inch 4-40 machine screw
5			4-40 nut
5			4-40 lockwasher
2			Shoulder Washer
2			Insulator, TO-218 size
1			Cable Clamp
2			Red Wire, 18 AWG
1			Yellow Wire, 18 AWG
1			Orange Wire, 22 AWG
2			Blue Wire, 18 AWG
1			Purple Wire, 22 AWG
2			Green Wire, 18 AWG
1			Black Wire, 18 AWG
1			Black Wire, 22 AWG
1			White Wire, 22 AWG
1			Gray Wire, 22 AWG
1			Resistor, 4.7 Ohm, 5%
2			Resistor, 47 Ohm, 5%
6			Resistor, 220 Ohm, 5%
1			Resistor, 330 Ohm, 5%
2			Resistor, 1k, 5%
2			Resistor, 1.1k, 5%
1			Resistor, 3k, 5%
1			Resistor, 6.8k, 5%
1			Resistor, 22k, 5%
1			Resistor, 47k, 5%
1			Resistor, 10k, 1%, metal film
1			Resistor, 47k, 1%, metal film

Note: The TIP33C and TIP34C have been discontinued and are generally not available anywhere. A wide range of power transistors will work, but they should be rated for at least 100V, 8A, and 80W power dissipation. Safe area operating curves and good thermal dissipation data are rarely available, so it's a guessing game. The more expensive TO-3 package parts, such as the MJ15003 & MJ15004 will certainly be more than sufficient for replacing the TIP33C & TIP34C. The only really compelling reason to use the TIP33C & TIP34C are because they cost less and come in a TO-218 package, which requires only one mounting hole.

Wire

  Diode assembly:         Gray 22 AWG (cathode)
                         White 22 AWG (annode)
 NPN Power Transistor:   Red 18 AWG (collector)
                         Orange 22 AWG (base)
                         Yellow 18 AWG (emitter)
 PNP Power Transistor:   Green 18 AWG (collector)
                         Violet 22 AWG (base)
                         Blue 18 AWG (emitter)
 Input Signal:           No wires, PCB mount jack
 Output Signal:          Blue 18 AWG (from PC board)
                         Black 18 AWG (from power supply)
 PC Board Power:         Red 18 AWG (to +35V on supply)
                         Black 22 Awg (to ground on supply)
                         Green 18 AWG (to -35V on supply)

Vendors

Mouser - 800-346-6873, 619-449-2222
Newark - 800-463-9275, 503-297-1984
Injectorall - 800-878-7227, 516-563-3388

Testing

If any of these tests fail, the amp is not constructed properly... the easiest and best way to find the problem is visual inspection.

Turn variable resistor fully counterclockwise (max resistance)
Connect to +/- 24 volt supply with 200mA current limit. No input and no output connected. Monitor current from power supply with a current meter.
Apply power... if current is above about 25 mA, shut off immediately!
Measure voltage across the 1k resistor connected to the input stage and Vcc. The DC voltage should be about 2 volt, or 2 mA of current through this resistor. Eg, if Vcc is at 24 volts, the side of this resistor connected to the 2N5210 transisor ought to be at about 22 volts.
Measure the DC voltage on the output line. It should be appox zero volts. -0.2 volts is probably fine.
Turn the variable resistor slowly until the amplifer's current consumption is approx 50 mA. Turn slowly and be careful... if you turn too far you could damage the output transistors.
Conect an oscilloscope to the output and apply a low amplitude 20 kHz square wave to the input. DO NOT connect any speakers during this test. This test should be done without the 330 pF capacitor installed. The amp should output a 20 kHz square wave with very little "ringing". It should not oscillate.
Solder the 330 pF capacitor into the circuit.
Shut off the power, connect audio input and a speaker. Make sure the volume is turned all the way down. Apply power... watch current meter again and shut off the power immediately if the current jumps to something much higher than 50 mA.
Slowly turn up the volume and see if the amp works. DO NOT turn it up very much... the amplifier should not be operated with a supply less than +/- 30 volts. It should never be used for high volume output without a power supply rated for at least 2 amps of current (8 ohm load). After this initial test with +/- 24V at 200 mA (current limited) only a proper power supply should be used which can provide enough current.

2.1 Channel Systems-Dual Power Amplifier TDA7240 and TDA1517

2009-01-03T15:58:00.006+07:00

The main problem with the design of stereo amplifier with a total bass driver, is that the signals of left and right channels, sooner or later, are summarized. As a result of merely adding up, the separation between channels is reduced to a minimum and violated the very idea stereofonii. The most efficient method of summation, known today - signal active smesitelyami - filters with high input impedance, which is often used by field-effect transistors. Subsequent cascades enhance increase the amplitude of the signal.

I tried to make some other way - most to weaken the signals of channels and to make their addition, as late as possible, before entering signal with high sensitivity (TDA 7240 - 46dB). The second chip-TDA 1517, serves as a mid-frequency driver.

I must say that the problem is not solved completely, the separation between channels is desirable to do more, subjective listening showed a contraction of panoramas, lack of air, which is inherent in amplifiers with independent channels. Listen to music using the device somewhat tiresome, but it very effectively transmits audio material of films and computer games. In any case, the amplifier has shown significant superiority over the multimedia system Logitech Z - 340, which is one of my friends recently bought for $ 60. Another nice time - managed to realize the possibility of simultaneous volume in all channels, which will agree, very convenient. Thus, the scheme was recommended for the recurrence of 2.1 Channel Systems, with the prospect of it improving.

Version 1
Version 2

USB DAC GC-PCM2706

2008-12-31T09:35:00.006+07:00

As General of the computer sound card if the total effect is generally not very good, often wear headphones to listen to a lot of strange sounds, if you want to do-it-yourself USB DAC to make best results, a USB PCM2702 DAC chip, such as the PCM2706 and ...

I had the choice of PCM 2706PJT, the use of its flexible than the PCM2702, and SPDIF output can I2S, IT is a monster, was the only word regarded as a fundamental element of the PCM2706 to say whether the voice of their own if Otherwise, leave a fiberglass production that we have received and then the GC-CAD V2.0 are very good. I want to strengthen the function, right! Try it! However, as a result of recent time is not enough, I do not have the full demand Zhanyou added, only the strengthening of the next.

1.Plus BNC coaxial output, the Council received a suspension of the BNC.

2.An increase in external power options, USB-General CAD is the use of USB directly to 5V power supply, but by the power of PC audio equipment may not always have the desired effect, I 'I am therefore of its external power supply, 3.3 V for the group 2 Power Supplies, a group of analog circuits for power, a group of digital circuits for power. COUNCIL PC and the lay-out discussion about the separation and a broken left on the hole, if you do not need external power, provided that it is broken, you can lower the volume.

The following are my last revised circuit:

The use of an external power L1117-3, the LDO 3V (voltage regulator IC), which is characterized by a low pressure difference, but only the best input voltage in the range of 4.8 to 6V, or I would during the process , The use of 12V DC adapter, power burn-L1117 at 3.3 V, burned on the exchange, burnt 7, the station is really great articles I bars.

The use of internal or external USB power to the circuit board to select Jumper, connect an external power supply for the employment of 1, 2, 2, 3 inserted in the internal use of USB power.

External power supply circuit left socket adapter, I had to stay 2 position, which one of you must also use their own elections in this direction for inserting the plug.

Fiber output can be used for the first TOTX178, 179,173, etc., fiber or compatible output of the first, I let you all types of electronic circuits in the first fiber-optic pin-compatible.

BNC BNC coaxial output is not directly in the main LAYOUT circuit board, I went to 2-pin, and then to people who can put on the chassis from outside the BNC or RCA Block.

As for the PCM2706 own production, I used the usual 3.5 mm headphone jack, if the direct use of computer speakers would be more practical, but it would be better received their best amplifiers.

Parts list is as follows:
R1, R2 ................................................ 15 Ω
R3, R4 ................................................ 22 Ω
R5, R6, R7, R8 ........................................ 3.3K
R9 .................................................... 1M
R10, R11 .............................................. 1.5K
R12, R13 .............................................. 330 Ω
R14 ................................................... 100 Ω

C1, C2, C3, C4 ........................................ 1uF/16V
C5,C6 C5, C6 .......................................... 47uF/16V
C7, C8 ................................................ 0.022uF (223)
C9, C10 ............................................... 100uF/16V
C11, C12 .............................................. 27P
C13 ................................................... 0.1uF grass-roots

U1 .................................................... PCM2706PJT
U2 .................................................... TOTX178 or compatible, and so on

LED ................................................... 3mmLED
L1, L2 ................................................ BEAD (core)
S1 ~ S7 ............................................... Small button switch
J1 .................................................... 3.5MM stereo headphone jack
J2 .................................................... USB-B-type outlet
CON1 .................................................. 2PIN pin Block
XTAL1 ................................................. Crystal 12Mhz
JP1, JP2 .............................................. 3PIN pin Block

Parts of the following non-necessary items, the use of an external power supply when the need for the following parts:

C14, C16, C18 ......................................... 100uF/16V
C15, C17 .............................................. 0.1uF grass-roots
P1 .................................................... 2.0mmDC Power Block
U3, U4 ................................................ L1117-3.3V

The following is a Upon completion of the photo:
The first test done PCM2706 USB DAC
Then do the PCM2706 USB DAC

Due to the use of two-panel design, so even if you have to DIY circuit board, to be careful on the hole well, in the welding must also pay attention to board up and down side through the hole to connect, it is necessary to carefully, one by one spot , The top hole through the use of the welding I am fine copper (from the general removed the suspicious wire to the more than OK fine line), the first place through the hole and then welding, if there are places that hole capacitor, such as the outlet can not be double-sided The welding parts, but also to use such a lead through the first, in front of the hole to find places to foil next to the weld can not play other parts had to hole-blocking, if that hole is the resistance, the switch , And so on .. core, it can be a double-sided welding. If the plant is the system board, then of course there will be no hole through the problem.

In fact, such a small cost to achieve External computer audio, CP is a very high value, do not want to spend a lot of money, you want to burn the little DIY, can be said to be a good choice.

If you download the PDF file is in the next few pages, you can see the film circuit board files, printed automatically canceled when the zoom function to print 1:1.

Download PDF version: GC-PCM2706USBDAC-FL.pdf
Film file to download: PCM2706D-BL.pdf

Superb Power Amplifier using TDA7250

2008-12-31T06:18:00.004+07:00

This 2-channel hybrid IC is normally configured with TIP142/147 power darlingtons for its' output. For those who prefer to use power transistors instead, the TDA7250 can easily be converted. All that is required are a few transistors, 4 additional resistors and some rewiring.

This conversion centers mainly on changing the output section to a Sziklai.

Sziklai Output

In our IA502 on the right, drivers Q1,Q2 are 2SC2238 and 2SA968, and outputs Q5,Q6 are 2SA1216 and 2SC2922 respectively.

No instability problems were encountered from this conversion. After a period of run-in, the amplifier remained thermally stable.

Is this version worth the extra cost and effort?

If one is only interested in something basic, the TIP version would be sufficient. But if one is after sonic performance, I would recommend this version.

2SC2922/2SA1216 hardwired

the TDA7250 ic

2SJ113/2SK399 SEPP AB-40W stereo power amplifier, no feedback, the DC system

2008-12-24T05:08:00.003+07:00

MJ wireless experiment in 1992 and announced in June

MOS-FET power output stage, a simple voltage・Miller called the NFB minor loops in multiplied by a powerful, and put on overalls with the NFB, has achieved very low output impedance, the natural sound of the amplifier.

Lead chassis S4 (300 × 200 × 60) is used. Both sides in the handmade SHIMASHITA wood paneling.

Block on the chassis are amplified voltage capacitors and a small stage for those who for the power transformer and the radiator and looks imposing, but the real thing is compact and lightweight.

Input terminals and output terminals to a lot of effort SUPATORON.

At the bottom of the radiator board配SHI MOS-FET power output stage and to shorten the wiring, the gate入RENAKU series resistance does not even oscillation.

Just change a little wiring, the source follower circuit voltage circuits in the mirror can be changed.

Miller-voltage operating conditions of the basic design is satisfactory, the source follower to change to get high-quality sound.

Miller-voltage circuit

Miller-voltage circuit and, as shown in Figure 1, MOS-FET source follower circuit and facing each other, the zero-bias operation to add J-FET, multiplied by the output stage to return to the local circuit.

[Figure 1] The output stage of the library

J-FET drain side of the drive and a collector of Tr-stage gate MOS-FET, so it is high impedance.
Pch Nch of the J-FET drain and between the MOS-FET INBIDANSU low bias power are combined with V B.

Therefore, the drive signal from the current stage, I S, J-FET to the source of the flow resistance R S, J-FET source of the signal voltage V S to occur, MOS-FET to the source of power equal to V S V O voltage can be obtained.

J-FET drain side of the higher impedance Z D, the output impedance of Z O will be reduced, MOS-FET input capacity of Cis (all seen from the side of the gate capacity, and will include feedback capacity) to I see a higher frequency and lower Z D, Z O increases.

MOS-FET gate - source voltage V GS, at a maximum and not more than V B, the maximum drain current I D is limited in quantity, so the effect of preventing excessive current may have up to two out of The current limit action in the clip must be designed to SHIMAWANAI.
The MOS-FET, the threshold voltage V GS (th) g m and the highest transconductance is desirable.
Fortunately, switching for the rich in power MOS-FET, but the request was consistent with many.

The design of this machine

MOS-FET used in Hitachi 2SJ113/2SK399 to.
Figure 2 shows the transmission characteristics.

1A and the idling current I O and Figure 2 and V GS is the extent to 5V, V B of the V GS is about twice the 10V.

[Figure 2] 2SJ113/2SK399 *V GS-I D* characteristics of

V GS to take a maximum of 2SJ113/2SK399 the aforementioned principles of the V B is less than 10V.

V GS in the case of a 9V about 9A So I D, 2Ω load resistance of the output voltage is also available in 18V, low enough to bear the load impedance.

For the basic design of the circuit is shown in Figure 3.
[Figure 3] The basic design of this machine

Power transformer, the tango TOROIDARUTORANSU using the RS-3101, the output stage supply voltage V DD is about 32V.

I O V B significantly higher if you set it, I D at the current clip can be larger, while the MOS-FET to increase the amount of heat, P CH channels of loss over the amount of allowable because This machine, and I O is 1A.

[Figure 4] heat dissipation design
Table 1 from the standard table P CH = 100W (Ta = 25 ℃), T CH = 150 ℃, so Heat inside the θ i resistors θ i = (T CH - T a) / P CH = (150 ℃ - 25 ℃) / 100W = 1.25 ℃ / W. DENKA TO-3P heat sheet using the MOS-FET and the thermal resistance between the radiator, Contact thermal resistance thermal insulation resistance θ c + θ s = 0.75 ℃ / W. Below is a circuit diagram of the heat conduction.

P CH = V DD I C = 32V × 1A = 32W, so Radiator will be allowed to seek maximum temperature T f, T f = T CH - P CH (θ i +θ c +θ s =150℃ -32W×(1.25℃/W +0.75℃/W ) = 86℃ Ta ambient temperature of the radiator in the case of 50 ℃, The maximum permissible radiator heat resistance, θ f = ( T f - T a )/ P CH = ( 86℃-50℃ )/32W =1.125℃/W

Figure 4 design radiating from the radiator to keep the temperature must be below 86 ℃.
Therefore, the radiator of a flexible TF1212 (122x120 × 40) in four pieces, MOS-FET is attached by a single, open-style chassis and put on.

Bias circuit as shown in Figure 5, V B less than 1 ~ 2V zener diode voltage and low anti-adjustable instrument (VR) has been able to adjust.

[Figure 5] Bias Circuit

The circuit and cause a bad contact VR, I O is on the rise as a dangerous, VR is reliable in use. CRD Diode, SEMITEC Japan = E102 0.88 - 1.32 mA, 10V

The constant voltage bias circuitry to operate a minimum of about 2mA current I L.

Miller-voltage circuits used in the local feedback 2SJl08/2SK370 of the J-FET I DSS 5.5mA is ranked GR, g m and the same amount if I DSS, and other forms of J-FET is also available.

The output stage for a full swing to V S necessary, to afford to ± 30V, R S at the time that I S 2.2kΩ is in full swing is ± 14mA.
When you, 2SJl08/2SK370 current flowing through the gate area covered Tr, is the gate to the low-impedance does not affect operation.

Tr stage of the drive for the operating current I S I S I SO that is half the 7mA, drive circuit and locally Biasing stage of the J-FET feedback circuitry necessary to operate because of the current sources of supply, drive stage Tr I DO idling current of the
I DO > I L + I DSS + I SO I DO> I L + I DSS + I SO
= 2mA+5.5mA+7mA = 2mA +5.5 mA +7 mA
=14.5mA = 14.5mA

'91 Of the amplify circuit voltage in the February issue of its MOS-FET DARINTONANPU INBATEDDO as well as two-stage amplification of the no-return.

FET first dan level of the output stage with zero bias 2SJ108/2SK370 behavior is the same.
Figure 3 is a constant,
I DO = ( R D・I DSS - V BE ) / R E I DO = (R D I DSS - V BE) / R E
=(1kΩ×5.5mA-0.6V)/0.27kΩ = (1kΩ × 5.5mA-0.6V) / 0.27kΩ
=18mA = 18mA
Thus, the above conditions are satisfied.
If I DSS is a small increase in R S and will need constant change.
In addition, R S of the increase can be, if滅RASHITA Conversely, 1.8kΩ below the oscillator to the output stage.
NFB also put to the Ministry of voltage amplification, or as the output stage of the oscillation Darlington to make it easier to connect.
Such circuits, in order to prevent oscillation, MOS-FET and the gate necessary to insert a resistance in series there.

The circuit of the machine

All of the library circuit is shown in Figure 6.

[Figure 6] The circuit of the machine

Amp circuit parts

Change of source follower

Part of the power circuit
The amplification of the first dan level voltage, FET to cover the cascode-voltage connection was made.

To amplify the power of the voltage, the power to reduce noise and crosstalk, CR put filters.

To prevent oscillation, MOS-FET's drain and capacitor ground connection between the wiring to a minimum.
This type of capacitor used in a significant impact on the stability of this machine 1μF use of multilayer ceramic capacitors, in a square wave output waveform was able to reduce ringing.

In making this standard to guarantee performance, Tr KONPURIMENTARIPEA and keep FET using a commercially available, and no resistance to the 5 percent level used in the selection.
A pair of strict screening device, and using high-precision resistance, to get the balance of push-pull, you can further reduce distortion.

The machines used in the standard device is shown in Table 1.
In addition, the unit of the standard elements of a possible substitute.
[Table 1] FET, Tr standards

Maximum Ratings (Ta = 25 ℃, * Tc = 25 ℃)
Electrical Characteristics (Ta = 25 ℃)

V GDS
I G
P D
T j
I DSS
g m
C is
Electrodes connected
Model name
(V)
(mA)
(mW)
℃
(mA)
(mS)
(pF)
2SJ108
25
-10
200
125
-2.6～ -20
22
105
2SK370
-40
10
200
125
2.6～20
2.2
30
DGS

V DSS
I D
* P CH
T CH
V GS(th)
g m
C is

(V)
(A)
(W)
℃
(V)
(S)
(pF)
2SJ113
-100
-10
100
150
-2～ -5
2
1100
2SK399
100
10
100
150
2～5
2
800
GDS

V CEO
I C
P C
T j

f T
C ob

(V)
(mA)
(mW)
℃
h FE
(MHz)
(pF)
2SA1015
-50
-150
400
125
70～400
>80
4
2SC1815
50
150
400
125
70～700
>80
2
ECB

V CEO
I C
P C
T j

f T
C ob

(V)
(mA)
(W)
℃
h FE
(MHz)
(pF)
2SA1360
-150
‐50
5
150
150
200
2.5
2SC3423
150
50
5
150
150
200
1.8
ECB

[Table 1] FET, Tr standards
	Maximum Ratings (Ta = 25 ℃, * Tc = 25 ℃)	Electrical Characteristics (Ta = 25 ℃)
	V GDS	I G	P D	T j	I DSS	g m	C is	Electrodes connected
Model name	(V)	(mA)	(mW)	℃	(mA)	(mS)	(pF)
2SJ108	25	-10	200	125	-2.6～ -20	22	105
2SK370	-40	10	200	125	2.6～20	2.2	30	DGS
	V DSS	I D	* P CH	T CH	V GS(th)	g m	C is
	(V)	(A)	(W)	℃	(V)	(S)	(pF)
2SJ113	-100	-10	100	150	-2～ -5	2	1100
2SK399	100	10	100	150	2～5	2	800	GDS
	V CEO	I C	P C	T j		f T	C ob
	(V)	(mA)	(mW)	℃	h FE	(MHz)	(pF)
2SA1015	-50	-150	400	125	70～400	>80	4
2SC1815	50	150	400	125	70～700	>80	2	ECB
	V CEO	I C	P C	T j		f T	C ob
	(V)	(mA)	(W)	℃	h FE	(MHz)	(pF)
2SA1360	-150	‐50	5	150	150	200	2.5
2SC3423	150	50	5	150	150	200	1.8	ECB

The production of this aircraft

A4-size chassis lead the S4 (300 × 200 × 60).

Impossible without wiring and components acrobatics on the use of the mounting, as long as stylized as a result of how the parts are in place, but not from the beginning rather than in accordance with such style, the best components and circuitry It is thought to want a place. High-current circuit in order to shorten the wiring, 22000μF blocks of storage capacitors on the inside of the chassis.

Processing of the chassis, radiator and cooling radiator for the better part of the mounting, to increase stiffness of thick reinforced with aluminum angle.

YASURI chassis in the welding marks from flat paint and Trim can be
Decoration on the front of the word processor in a black plastic sheeting was printed in gold ribbon stickers on their own.

For the board, copper foil for printed circuit board wiring can not be used as a vapor.
As a result of the library board, as in Figure 7, the bull's-eye of the copper foil substrate in the etching solution to remove the lead wire through a hole in the expansion of 2mm in diameter, and bring out the wiring in place of a single wire fault of 0.8mm thickness Strange.

[Figure 7] of the library board
The upper parts of the board layout

Place the bottom part of the board	Change of source follower

MOS-FET from the board to speed up the wiring, the board placed part of the mounting position, I sent a particular concern.

Tr two-stage during the drive, angled aluminum heat sinks are attached to the tie, the heat of the earth plate connected to the substrate, and the chassis may not have any contact.

FET complementary characteristics , so the thermal drift, it is binding, so the heat on this machine is not binding.

Upper and lower parts of the substrate is mounted on both sides, and are cross-wired to the stereo, not making a mistake when you have good circuit diagram and to see that match.

Power supply circuit, the capacitor blocks from the terminal Rch Lch and wiring into two strains, and 100Ω power supply voltage amplifier attached to the plate to lag, the output of the idling current stage of the resistance to check the terminal block 0.47Ω Mounted on.

The output signal Q8, Q9 and the gate of 2.2kΩ extracted from the Earth's is a logical.
Therefore, Q10, Q11 from the source of Q8, Q9 Hye-wiring of the gate, which are then wired to the output pins.
But from the supply side of the Earth Hye 2.2kΩ, and the output pins and wiring.
Rectifier diode from the wiring to emit intense RIPPURUNOIZU other引KI回SHIMASU do not interfere with wiring.
MOS-FET gate of the current-carrying wires and open and the input capacity is in charge of the gate voltage to drain excessive current to flow, so beware of destruction.

Adjustment of the machine

Before the adjustment of the resistance VR 1 and VR 2 to leave the minimum value.

Turn the first time, in case of emergency drain and power MOS-FET 10Ω10W between the need to connect to the resistance.

Turn the output within ± 2V DC voltage, 10Ω peers verify voltage is less than 10V.
10Ω would remove the anomaly, the wiring back to normal.
The first adjustment, and idling for 1A current, VR 2 to adjust the voltage of 0.47V at both ends 0.47Ω.

If the VR 2, it is up to 0.47V If the VR 2 in the series with less than 1 ~ 2kΩ resistance in the case, contrary to 0.47V as VR 2 more than the minimum if the HZ-HZ-9L zener diode 7L exchange.

After idling 0.47Ω current settings and leave a short circuit.
DC output voltage to 0V and then to adjust the VR 1, but the power of the state暖MAっcold and heat until a stable condition change DC voltage output to 0V in any state. The machines fluctuation band around the center of the 0V.

Turn the VR 1 to increase output if the DC voltage, Q 1 source of 390Ω

After more than a measurement of adjustment, and later was able to get the property.

Changes to the source follower circuit

Lower SOSUFO If you compare the change in voltage that Miller was going to show excellence, excellence is fundamental to the circuit, the source follower of the great qualities who is also my best MASHITA.

Miller FOROWAHE voltage changes from the source, Figure 6, Figure 7, as shown in the return of local resistance to remove the FET switching can be a simple, so one can enjoy as much of the amplifier.

After the changes increase Idling a little current, so the re-adjustment is required.
In addition, changes to the circuit in the switch is no more acceptable.
The longer the oscillation circuit will be easier if the switch is running a poor contact and damage the cause of switching from the speakers.

In addition, a source follower of the voltage amplifier if you want to change the mirror, mirror voltage as the above-mentioned constraints must be met.

The characteristics of this machine

Figure 8 characteristics and the frequency of the Figure 9 crosstalk characteristics of the source and the voltage follower without a difference in the mirror, and accepted the good characteristics of the vocal cord is in the region.

RESUBONSU the high-growing region because of the high-frequency signals of the MOS-FET input current capacity can be passed through the gates - the source of signal voltage between the decrease in cost.

[Figure 8] frequency characteristics.

[Figure 9] characterization of crosstalk

Figure 10 is characteristic of the distortion, and frequency for each individual to move parallel to the low-voltage Mirror, low-frequency effects of a localized because of the high return rate is a low distortion.

[Figure 10] distortion characteristics

Figure 11・damping factor characteristic of the low-frequency BORUTE JIMIRA If there are more than 1,000 from 600Hz to 100kHz while much is falling in a straight line.
The cause, MOS-FET input will increase capacity and frequency for the local decrease in the amount of feedback.
Meanwhile, the case source follower, about 20 in the regional auditory zone is nearly constant. This is like a personality characteristics of each other's differences, which divide the sound quality is a factor.

[Figure 11] damping factor characteristics・

Then resist Load by 10kHz square wave output waveform of the load and capacity are shown in the photos.
Enlarge to rise again to display the waveform, the ringing is legible.

10kHz square wave output waveform Photo
SOSU・FOROWA	Miller voltage・
8Ω load 4Vp-p	8Ω load 4Vp-p

0.1μF load	0.1μF load

0.47μF load	0.47μF load

8Ω +0.1 μF load 4Vp-p	8Ω load 55Vp-p

Miller-source voltage follower and stability in both high-capacity load is not on the oscillation.
High stability and the improvement of property ambivalent relationship with, is a difficult balance.

The high-range aircraft to more than necessary that the property did not extend to higher depreciation was available taxis.

ON-OFF at the time of supply shocks 0.5Vp-p less noise and lower the residual noise Rch 140μV, Lch, and it also reduces the 130μV, and silence the cry of power transformer in the extra care.

The temperature of the radiator, but if you do not mind the location of the ventilation, can not be touched by hand and the heat is not enough.

The sound quality of the natural voltage moist Miller faction, the source follower and a faction a spectacular reduction of the thick, and to insist on individuality, both of which are difficult to discard, the悩MIMASU choice, but only if producers Can enjoy luxury.

Discreet Power Amplifier Great Sound and low cost

2008-12-24T04:46:00.002+07:00

Before proceeding further define discreet: Discreet is not continuous in mathematics relates to the natural numbers and whole and electronics is the central concept of a circuit implemented by the minimum component: transistors, resistors, capacitors, etc., without the use of integrated circuits that meet them within several of these components.

There are several series, the TDA, LM, STK, ... Its sound quality does not meet the required quality in the topic at hand. Because they are designed to get good numbers, do not focus on correcting distortions before they occur and are based on principle and expired in engineering in this field.

You need to do more instead of relying on the good performance feedback. The feedback correcting the distortion, but adds its own and this is the whiting that bites its tail, a club which adds distortion correction. The distortions produced by this technique are difficult to measure and almost never done, aside from the low correlation between the figures (THD, IMD ,...) and hearing as they are raised. Why do they sound good valves with THD between 0.3 and 3%?.

TDA7294 DC Servo Amplifier current negative feedback

2008-12-17T20:09:00.006+07:00

In the field of consumer reports electronics products reviews, product size, weight is toward smaller, lighter direction, high-power single-chip audio power amplifier needs of increasingly prominent, TDA7294 is currently the best performance, the biggest single-chip audio power amplifier One.

It consists of the European SGS-THOMSON Italian-French company in accordance with discrete components A and B audio amplifier circuit design from classic. Its former low-level noise, low distortion of the bipolar transistor circuit, at the end of a high-pressure, high current DMOS output of the buffer, it has bipolar circuit sounds pure merit, have large current high voltage FET Driver output characteristics.

Since 1998 TDA7294 introduced to China so far, I believe that many enthusiasts have been TDA7294 delicate taste, natural sound. Regrettably, however, is that they have heard only negative feedback is standard voltage of the voice amplifier.

And negative feedback amplifier voltage than current negative feedback amplifier as excellent transient nonlinear distortion and intermodulation distortion characteristics, the frequency amplifier curve flat, high and low frequency response more exhibition wide; more important is that circuit Will load impedance into the feedback network, it can change the speakers of such fierce resistance to the load compensation, coupled with stable and reliable performance, than the negative feedback voltage amplifier has more advantages, the current negative feedback current amplifier is widely For the modern high-fidelity audio amplifier.

Figure 1 circuit is an excellent performance, improve the design of the fever-100 W × 2 DC Servo Amplifier current negative feedback stereo amplifier, formed by the two TDA7294, the frequency response of 10 Hz ~ 100kHz. The use of sophisticated audio Yun-double as the two-channel amplifier DC Servo Amplifier output. Speakers from the protection of ASIC μPC1237HA driver completed the relay switch-mute and amplifier output DC offset protection, and other speakers. When the AC power plug, the relay will be delayed for some time speakers access amplifier; disconnecting the AC power when, μPC1237HA detected exchange loss, immediately disconnect the speaker to relay, the amplifier is the complete elimination of the set, Shutting down the transition process the impact of noise on the speakers.

In actual use, taking into account the electricity grid fluctuations Rectifier amplifier output voltage ± Vs volatile, in order to avoid over-voltage and high temperature in the state of damage TDA7294 (Note pressure in the temperature of 25 ℃ under the conditions, if the temperature exceeds 25 ℃, TDA7294 the value will subsequently reduce the pressure), the exchange recommended power supply voltage transformer CT-AC26V × 2.

Listen:

Speaker to use B & W601, CD machine Marantz CD-19, compared TDA7294 amplifier for the negative feedback standard voltage lines. Software programs at Cai Qin, "the film" test the human voice, Mutebutsi trial String, RR's "Tutti" dynamic test, Rubinstein "Chopin Nocturne" trial piano.

The results are as follows:

In a dynamic sense of speed, the two amplifier very close, but the sound on the current negative feedback is obviously more sweet; the string, the human voice like the rendering software for a warmer, the details of the re-orientation; due to current negative feedback circuit Impedance of the compensation, the low-band high-impedance output has been strengthened, so dive in the low-frequency and intensity of the depth occupied obvious advantage.

Current negative feedback in addition to direct stereo amplifier for CD, VCD, DVD, and other music source amplifier, but also with audio processing unit for use by different combinations of the playback effect.

Project of circuit potent audio amplifier with TDA7294

2008-12-13T04:51:00.003+07:00

Super Amplifier with tda7294 of the St microeletronics, is possible to get potency of up to 100W in an only chip, for an unit stereo to use two same to that. That circuit is based on the datasheet of the ready

to work with sources of strong signs, in case it is necessary it uses a pré-amplifier in the form of an opamp. That circuit type with integrated circuit is ideal for systems of involving sound. Because he is quite compact could use an independent amplifier for each one of the high speakers. In that way it can be to share the source dimensioned it is clear to support all the connected amplifiers. Oh you can remove a wave with that neighbor that bought a " home theater " of 1000W PMPO, and fear in saying that is an enormous potency, when in reality it will verify the real potency of the equipment it doesn't arrive nor to 10W RMS for channel. It already imagined a system of high active speakers with 80W. If it will pass for the marketing department, that where defines the potency PMPO, your system would give... it lets me to see... comparing with the example oh of top... about " 3000 W PMPO ". Game that you have been doing with the potency of the equipments. For you to do your sound system will only need the sign source. Because the amplifier can be perfectly that of here. The necessary subwoofer of a little more of potency then in the datasheet you will find an assembly example in bridge to increase the potency. Below we have the schematic, the Printed circuit board and details of the assembly.

Good luck.

schematic - diagram circuit for assembly power amplifier tda7294

Suggestion of Printed circuit board to assembly the power amplifier with tda7294

Side of the components to assembly potent amplifier with TDA7294

lists of components: for tda7294

C1 1µF
C2 47µF
C3 10µF
C4 10µF
C5 22µF
C6 4700µF/50V
C7 100N
C8 4700µF/50V
C9 100N
D1 1N4148
R1 22K
R2 680R
R3 22K
R4 22K
R5 30K
R6 10K
SL1 key de Mute
SL2 signal input (Line In)
U1 TDA7294V
X2 Connector AK300/3
X3 Connector AK300/2
several: Printed circuit board, power source +35 -35V / 6A, etc