Audio Circuits

Mini Audio Amplifier with LM380

2015-03-27T22:03:00.003-07:00

This is the very simple circuit of mini audio amplifier single channel / mono using low cost IC LM380. For stereo application, just build the identical circuit.

The circuit shown in Figure 1 is a very simple audio power amplifier. The main component of this circuit is the LM380 audio amplifier. The simplicity of this circuit is made possible by the LM380's minimal requirements for external components, since it is already internally equipped with the necessary biasing, compensation, and gain circuits for audio amplification.

The circuit in Figure 1 uses the LM380 in non-inverting mode, with the inverting input left open (the inverting input may also be tied to ground, either directly or through a resistor or capacitor). C2 is used to decouple Vcc from ground. The optional RC circuit at the output (pin 8) is used for added stability, i.e., to eliminate oscillations in an RF-sensitive application.

Figure 2 shows how the circuit in Figure 1 can have a variable gain simply by connecting a potentiometer across the inputs of the LM380. Rv is varied to adjust the gain of the amplifier.

250 milliwatts Amplifier with TDA2822

2014-11-19T00:36:00.001-08:00

This is 250 milliwatts amplifier scheme design with TDA2822. This low power amplifier generates 250 mW on each channel, can be used for general purposed application such as walkman, mp3 player, radio etc. This may well configured to operate in stereo or bridge, which is obtained more power in mono channel.

It is also ideal for use as a preamp in high power amplifiers. It can be supplied with 3 to 6 volts and 500 milliamps, without detracting from the quality of sound. It is useful to replace portable radios and amplifiers of gaming gadgets.

List of components:
R1, R2: 10 KΩ
R3, R4: 4.7 KΩ
C1, C2, C3: 10 uF. electrolytic capacitors
C5, C5: 1000 uF. electrolytic capacitors.
C6, C7: 0.1 uF. ceramic capacitors.
IC1: TDA2822
B1: four 1.5 volt batteries or a power supply 6 volts.
LS1, LS2: Speakers or 4 Ω speakers.

Echo Chamber Schematic Diagram

2014-06-22T23:12:00.001-07:00

This is the schematic diagram of echo chamber circuit which will convert the input sound to have echo sound just like if you talking in the cave. This echo chamber circuit can be applied on any source of audio signal like microphone, mp3 player, radio, etc. The aims is smoothing the voices with echo.

The MN3005 is a world’s first 4096-stage long delay BBD, 8 times longer than S12-stage BBD manufactured by using a P-channel low noise silicon gate process.

Long signal delay time 205ms can be obtained at clock frequency 10KHz. S/N is 75dB. S/N has been improved by more than 20dB in comparting with 8~connected S12-stage BBD’s.

The MN3005 is suitably used for reverberation and echo effects in electronic musical instruments such as electronic organ, guitar amplifier and music synthesizer which need long delay time.The MN3101 is a CMOS LSI generating two phase clock signal of low output impedance to drive MN3000 series BBD. Built-in VGG power supply circuit for the MN3000 series BBD* provides most suitable VGG voltage for the BBD when the MN3101 is used with the same power source as BBD. Oscillation is abled by external resistors and capacitors, and also oscillation drive is possible by the separate excitation oscillation. Clock signal frequency is 1/2 of oscillation frequency.

Components List:

R1____________________________22K
R2, R3_________________________4K7
R4____________________________1K
R5____________________________82K
R6, R13, R19____________________47K
R7, R12, R23, R25________________120K
R8, R15, R16____________________100K
R9, R10________________________56K
R11, R12_______________________33K
R14___________________________15K
R17, R18_______________________5K6
R20, R21_______________________39K
R24, R26, R28___________________220k
R27, R29_______________________10K
C1, C18________________________2K2
C2____________________________1uF/16V
C3, C6, C7, C13__________________3,3uF/16V
C15, C16, C22, C23_______________3,3uF/16V
C4____________________________470pF
C5____________________________1K
C8, C9, C10_____________________3K3
C11, C12, C20___________________220pF
C14___________________________820pF
C17___________________________1K8
C19___________________________4K7
C21___________________________47K
C24___________________________100uF/16V
VR1___________________________200K
VR2___________________________10K Pot B
VR3___________________________20K
VR4___________________________100K
D1____________________________1N4148
D2____________________________9V Zener Diode
TR1___________________________C536
IC1, IC4_______________________AN6651
IC2___________________________MN3005
IC3,__________________________MN3101

Electronic Stethoscope Circuit

2012-08-18T00:24:00.001-07:00

This is an electronic stethoscope circuit diagram. The operation of the circuit is very simple. It's work is similar to general home audio system. The heartbeat sounds catched by electret microphone and then the amplifier amplify the signal.

Component List:
R1 = 10K 1/4W
R2 = 2.2K 1/4W
R3, R9 = Not used
R4 = 47K 1/4W
R5, R6, R7 = 33K 1/4W
R8 56K = 1/4W
R10 = 4.7K 1/4W
R11 = 2.2K to 10K audio-taper (logarithmic) volume control
R12 = 330K 1/4W
R13, R15, R16 = 1K 1/4W
R14 = 3.9 Ohm 1/4W
C1, C8 = 470uF/16V Electrolytic Capacitor
C2 = 4.7uF/16V Electrolytic Capacitor
C3, C4 = 0.047uF/50V Metalized plastic-film Capacitor
C5 = 0.1uF/50V Ceramic disc Capacitor
C6, C7 = 1000uF/16V Electrolytic Capacitor
U1 = TL072 Low-noise, dual opamp
U2, U3 = Not used
U4 = 741 opamp
U5 = LM386 1/4W power amp
MIC = Two-wire Electret Microphone
J1 = 1/8" Stereo Headphones Jack
LED = Red/green 2-wire LED
Batt1, Batt2 = 9V Alkaline Battery
SW 2-pole, single throw Power Switch
Misc. Stethoscope head or jar lid, Rubber Sleeve for microphone.

How the Circuit Work:
U1a runs as a low-noise mic pre-amplifier. Its gain is only about 3.9 because the high output impedance of the drain of the FET inside the electret mic causes U1a’s effective input resistor to be about 12.2K. C2 has a fairly high value in order to pass very low frequency (about 20 to 30Hz) heartbeat sounds.

U1b runs as a low-noise Sallen and Key, Butterworth low-pass-filter with a cutoff frequency of about 103Hz. R7 and R8 provide a gain of about 1.6 and allow the use of equal values for C3 and C4 but still producing a sharp Butterworth response. The rolloff rate is 12dB/octave. C3 and C4 can be replaced with 4.7nF to increase the cutoff frequency to 1KHz to hear respiratory or mechanical (automobile engine) sounds.

The U4 circuit is optional and has a gain of 71 to drive the bi-colour LED.

U5 is a 1/4W power amplifier IC with built-in biasing and inputs that are referred to ground. It has a gain of 20. It can drive any type of headphones including low impedance (8 ohms) ones.

Assemble Notes:

Assemble the circuit using Veroboard (stripboard) or a PCB.
Use a shielded cable for the microphone as shown on the schematic.
Fasten the microphone to the stethoscope head with a rubber isolating sleeve or use a short piece of rubber tubing on its nipple. A thick jar lid can be used as a stethoscope head. The microphone must be spaced away from the skin but the stethoscope head must be pressed to the skin, sealing the microphone from background noises and avoiding acoustical feedback with your headphones.
The microphone/stethoscope head must not be moved while listening to heartbeats to avoid friction noises.
Protect your hearing. Keep the microphone away from your headphones to avoid acoustical feedback.

Simple Pre-Amp with One Transistor

2012-05-24T19:33:00.001-07:00

This is a very simple pre-amp circuit which use a transistor as a active component to boost the input signal. Its simplicity makes this circuit easy to built and inexpensive. The microphone used in this circuit is electret type which is very sensitive detecting the sound around its.

It require 3-9V DC power supply with small power consumption.

Stereo OTL Audio Amplifier

2012-04-22T18:58:00.001-07:00

The following diagram is the circuit of Stereo OTL Audio Amplifier. It based on IC circuit, so the circuit looks simple. You can use IC LM379,LM377,LM378 for this amplifier project.

Refer to the table, maximum voltage supply for IC LM379 is 28V, it will will deliver 4W/channel. For LM377, maximum Vcc voltage is 18V single supply and delivers about 2W/channel. While for LM378, use maximum 24V regulated DC power supply and you will get 3W hifi audio power per channel.

Use heatsink on the IC to prevent overheating.

Mini Micropone Amplifier Circuit

2012-04-04T20:43:00.001-07:00

This is the schematic diagram of mini microphone amplifier circuit, which all of the active components are based on transistor. This circuit project is called "mini" since its size is small and the output is small too. It uses surface mount technology.

Circuit works

The output is push-pull and consumes less than 3mA (with no signal) but drives the earpiece to a very loud level when audio is detected.

The whole circuit is DC coupled and this makes it extremely difficult to set up. Basically you don't know where to start with the biasing. The two most critical components are 8k2 between the emitter of the first transistor and 0v rail and the 470R resistor.

The 8K2 resistor across the 47u capacitor sets the emitter voltage on the BC547 and this turns it on. The collector is directly connected to the base of a BC557 transistor, called the driver transistor. Both of these transistors are now activated and the output of the BC557 causes current to flow through the 1k and 470R resistors so that the voltage produced across each resistor turns on the two output transistors. The end result is mid-rail voltage on the join point of the two emitters. The 8K2 feedback resistor provides major negative feedback while the 330p prevents high-frequency oscillations occurring.

120W Power Amplifier Circuit - Leach Amp

2012-03-14T20:30:00.002-07:00

Here the 120W power amplifier claimed to be a very good sounding design.

The circuit is complex, so it will hard enough to build manually by yourself. The design of PCB layout is already presented, but it still hard enough to construct. I do not recommend that you create the circuit boards unless you have experience in doing it.

A source of materials for making your own printed circuits can be found here. I have been told that their "Press and Peel Blue" product (not the wet stuff they sell) can be used to successfully make boards with traces as narrow as 0.01 inch. The smallest traces on the amplifier layout are 0.03 inch wide. The PnP Blue product is basically a transfer medium that allows you to transfer the toner image from a laser printer directly onto bare copper clad board and then etch it with FeCl3 (ferric chloride). This is nasty stuff and it should not be disposed of in your drain.

Electric Guitar Preamplifier Circuit based TL071

2012-02-23T16:19:00.000-08:00

Right here is definitely the circuit of a electric guitar preamplifier circuit based TL071 that would accept any common guitar pickup. It's also versatile in that it has two signal outputs.

A common illustration of working with a pickup attached to a guitar headstock is shown in above image. The pickup unit contains a transducer on one end and also a jack on the other end. The jack can be plugged right into a guitar preamplifier circuit and then to a power amplifier system.

The pickup unit captures mechanical vibrations, generally from stringed instruments for example guitar or violin, and converts them into an electrical signal, which could then be amplified by an audio amplifier unit. It is most often mounted on the body of the music instrument, but may also be attached to the bridge, neck, pickguard or headstock.

The primary part of this preamplifier circuit shown in above circuit diagram is a single-transistor common-emitter amplifier with degenerative feedback in the emitter and a boot-strapped bias divider to safe optimum input impedance. Using the component values shown right here, the input impedance is higher than 50 kilo-ohms and the peak output voltage is about 2V RMS. Master-level-control potensiometer VR1 needs to be fine-tuned for minimal distortion.

The input from guitar pickup is fed to this preamplifier at J1 terminal. The signal is buffered and processed by the op-amp circuit wired close to IC TL071 (IC1). Set the gain utilizing preset VR2. The circuit has a master and a slave control. RCA socket J2 is the master signal output socket and socket J3 is the slave.

It really is considerably better to take the signal from J2 as the input to the audio power amplifier system or sound mixer. Output signals from J3 can be utilized to drive a regular headphone amplifier. Working with potensiometer VR3, set the slave output signal level at J3.

Assemble the circuit inside a metallic case. VR1 and VR3 ought to preferably be the types with metal enclosures. To avoid hum, ground the case and the enclosures. A well-regulated 9V DC power supply is important for this circuit. Even so, a standard 9V alkaline manganese battery may also be put into use to power the circuit. Switch S1 is a power-on/off switch.

Electric guitar preamplifier circuit based TL071, source: EFY Magz

UM66 Music Generator Circuit

2012-02-19T15:01:00.000-08:00

This is the UM66 music generator circuit, of course this circuit uses UM66 as the main component to generate the signal of music / melody. UM66 operates on a supply voltage of 3V. The required 3V supply is given through a zener regulator. The transistor Q1 and Q2 is a push pull amplifier to drive the loudspeaker, so the music signal from pin 1 IC UM66 can be heard loudly. A class A amplifier can be used before push pull amplifier to minimize the noise and improve the output sound quality. UM66 is a 3 pin IC package just looks like a BC547 transistor.

Components list:

R1 = 4.7K
C1 = 10uF-25v
D1 = 3.3v Zener
Q1 = SK100
Q2 = SL100
IC = UM66
SP = 8 ohm

UM66 Pin Configuration:

Output : Melody Output
+Vdd : Positive power supply
-Vss : Negative Power supply

UM66T Features:

Voltage rating: 1.3V to 3.3 V
62 Note ROM Memory
Power on reset

Multitone Alarm Sound Generator

2012-02-12T19:53:00.000-08:00

Here the Multitone Alarm sound generator. This kind of multitone alarm is useful for security alarms, reverse horns, and so on. It generates five various sound tones and is also considerably more ear-catching when compared to a single-tone alarm.

The circuit is constructed close to well-known CMOS oscillator-cum-divider IC 4060 and small audio amplifier LM386. IC 4060 is utilized as the multitone generator. A 100 µH inductor is utilized at the input of IC 4060. Therefore it oscillates within the range of about 5MHz Radio frequency. IC 4060 itself separates RF signals into AF and ultrasonic ranges. Audio signals of various frequencies can be obtained from pins 1, 2, 3, 13 and 15 of IC 4060 (IC1). These kinds of multifrequency signals are mixed and given to the audio amplifier designed close to IC LM386.

The actual output of IC2 is given towards the loudspeaker through capacitor C9. If you need louder sound, work with power amplifier TBA810 or TDA1010.

Only five outputs of IC1 are being used because the other five outputs (pins 4 through 7 and also 14) generate ultrasonic signals, which aren't hearable.

Construct the circuit on a general-purpose Printed Circuit Board and enclose inside a appropriate cabinet. Regulated 6V-12V (or a battery pack) can be used to power up the circuit.

Multitone Alarm Sound Generator Circuit Source: Electronics For You

Steam Whistle Sound Generator Circuit

2012-02-04T15:54:00.000-08:00

This is the circuit diagram of steam whistle sound generator. This circuit contains six square wave oscillators. Square waves are composed of a huge variety of harmonics. If six square waves with various frequencies are added collectively, the final result is going to be a signal which has a very large number of frequencies. When you listen to the result you will find out that it happens to be very identical to a steam whistle sound. The circuit ought to be beneficial in modelling or even in a sound studio. This circuit works by using only two ICs. The first IC, a 40106, consists of six Schmitt triggers, that are all set up as oscillators. Various frequencies are produced from the utilization of various feedback resistors.

The output signals from the Schmitt triggers are mixed via resistors. The resulting signal is amplified by IC2, an LM386. This IC can deliver audio power of about 1 W , which should be enough for driving the loudspeaker for most sound related electronic circuit. In case you leave out R13 and all parts after P1, the output can then be connected to a more strong amplifier. In this way a definitely deafening steam whistle could be made. The ‘frequency’ of the signal could be altered with P2, and P1 is used to control the volume.

Steam whistle sound generator circuit source: extremecircuits.net

High Gain Stereo Tube Preamplifier

2012-01-28T08:46:00.000-08:00

This is the circuit diagram of stereo tube preamplifier, give you high gain with high performance output. This circuit should work fine with a 6J5, 12SX7, 6CG7, or 12AU7 as the lower tube, and a 6BX7, 12B4, or triode-connected 6BQ5 as the upper tube. Any of the miniature TV dual triodes such as 6DE7 or 6EW7 can serve as both top and bottom triodes since they contain a medium-mu and a low-mu section. (This wouldn't be my choice, since the octals seem to sound better, but you may choose the tubes you like.)

Tube Preamplifier Parts List:

R1,R5 = 100 1/4W carbon
R2,R6 = 100 1W metal film
R3 = 1M 1/4W metal film
R4 = 10k 25W wirewound
R7 = 10k 1/2W metal film
VR1,VR2 = Part of Alps quad volume/balance control
C1 = 2uF 400V polypropylene
C2 = 10uF 400V polypropylene
V1 = 12SN7GT (GE) or 6SN7GT (see text)
V2 = 6BL7GT (GE)

This circuit require special power supply circuit. The power supply is regulated, has slow warmup inherent in its operation. The power supply for this tube preamplifier is in simply designed. The tube 6AS7G for looks; it's much bigger and lights up more impressively than a 6080. The only problem was with the voltage standard since gas tubes are capable of impressive noisemaking.

Power Supply Parts List:

R1 = 10 1/2W metal film
R2,R3 = 20k 10W wirewound
R4 = 10k 1/4W metal film
R5 = 18k 1/2W metal film
R6 = 56k 2W metal film
R7 = 27k 2W metal film
C1 = 10uF 400V polyprop
C2 = 220uF 400V electrolytic
C3 = 0.1uF 400V Mylar
C4 = 2uF 400V polyprop
T1 = power transformer, 250-0-250V 50mA, Thordarson 24R09 or similar
T2 = filament transformer, 24V CT 2A, Mouser 41LK020 or similar
L1 choke, 20H 50mA, two Triad C-3X in series (see text)

Other components needed: (8) ceramic octal sockets, (5) 7-position ceramic terminal strips, (6) chassis-mount RCA sockets, aluminum chassis 15" 4" 3", AC power cord with strain relief, knobs for pot, DPDT miniature switch, Teflon-insulated wire, 1/4" copper tubular braid, stereo 1/4" panel-mount phone socket, assorted hardware.

Read more about High Gain Stereo Tube Preamplifier, visit this page

2x6W Stereo Audio Amplifier based LA4440 Power IC

2012-01-21T01:58:00.000-08:00

This is the diagram of 2x6W stereo audio amplifier based LA4440 power IC. Actually, the LA4440 can be used in both stereo mode and mono (bridge) mode, but the circuit presented in this post is LA4440 in stereo mode. The recommended power supply is 13.2V, while the maximum voltage rated at 18V.

LA4440 Features:

Built-in 2 channels (dual) enabling use in stereo and bridge amplifier applications.

Dual : 6W´2 (typ.)
Bridge : 19W (typ.)

Minimum number of external parts required.
Small pop noise at the time of power supply ON/OFF and good starting balance.
Good channel separation.
Good ripple rejection : 46dB (typ.)
Low distortion over a wide range from low frequencies to high frequencies.
Small residual noise (Rg=0).
Easy to design radiator fin.
Built-in protectors.
Built-in audio muting function.

Thermal protector
Overvoltage, surge voltage protector
Pin-to-pin short protector

50W Power Amplifier Circuit using STK084

2012-01-13T04:26:00.000-08:00

This is the circuit diagram of 50W power amplifier circuit which built based on single power amplifier chip of STK084. It's an well-known old IC for audio frequency (AF) amplifier.

This circuit requires dual polarity / split power supply with maximum supply of ± 50. The recommended supply is ± 35 / 2-3A DC current. You may use this split power supply circuit for the amplifier. Use 28V center tap transformer to get about ± 36V output.

Technical Details:

Power output: 50W
RL : 8 Ohm
TDH : 0.2 %
Rin : 52K
Gain : 26.4 dB
Noise : 0.3 mV

Take a note that heatsink is required to be mounted on the power IC since it will going to hot when operated and deliver high power output (high audio volume level).

50W Audio Amplifier Circuit

2012-01-08T02:38:00.000-08:00

Here the 50W audio amplifier circuit diagram. The amplifier is based ICL8063. This a good amplifier circuit which is easy enough to built.. This circuit can be connected by radio, TV, stereo or other devices.

The circuit is also featured with inputs for the record player, guitar, microphone, and others. If you add low pass filter at the input, it will work like a mini-subwoofer. Circuit scheme presented will guide you in 50W amplifier construction, good luck.

The power supply is splitted type, already added on above circuit diagram.

Components List:

R1 = 200R 1/4W
R2 =200K 1/4W
R3 = 30K 1/4W
R4 = 1K 1/4W
R5 = 5K 1/4W
R6, R9 = 1M 5% 1/2W
R7, R8 = 0,4 ohm 5W
R10 = 10K Pot
R11, R12 = 51K 1/4W
R13 = 47K 1/4W
C4, C6, C5, C7, C8 = 1nF
C9 = 50pF
C10 = 0,3uF
C11, C12 = 10000uF/50V
U1, U2 = IC 741 Op Amp
U3 = ICL8063
Q1 = 2N3055 NPN Power Transistor
Q2 = 2N3791 PNP Power Transistor
D = 250V 6A Bridge Rectifier
T = 50V Center Tapped 5A Tranformer
C1 = 100uF/35V
F1 = 2A Fuse
C2 = 11nF
SPEAKER = 8 ohm 50W
C3 = 3750pF
Heatsinks For Q1 and Q2

Enhanced Hafler Matrix Surround Sound Decoder

2012-01-02T14:19:00.000-08:00

This is the circuit diagram of enhanced Hafler Matrix surround sound decoder. The above schematic can be a basic technique to attain exactly the same factor (with some extra rewards) at line level (i.e. prior to the signal reaches the power amplifiers - in a bi-amped method, this circuit should be in between the preamp along with the electronic crossover). The extras obtainable are readily apparent:

Wiring is simplified (despite the fact that extra power amplifiers are necessary)
We now have a centre channel signal accessible
Provision for a mono signal to a sub-woofer is simple

Though there have been comparable circuits published more than the years, this can be slightly unique in several locations. I wanted to prevent getting any active electronics inside the key Left and Right channels, due to the fact this eliminates any possibility of sound degradation because of the introduction with the op-amps. The input impedance of 50k won't pose an issue for any pre-amp (such as valve sorts), as well as the principal signal is merely in parallel using the extra circuitry.

No volume control has been integrated, due to the fact you already have one inside the pre-amp circuit. It would just turn into one more component to fiddle with, and due to the fact it could be hardly ever applied, would most likely develop into noisy as time passes.

How the Circuit Works
Opamp U1A is connected as a subtracting amplifier. Really should exactly the same signal be applied to each inputs, the output is zero. Because of this, it'll eliminate all popular data from the stereo signal, and reproduce only the distinction signal - in specifically exactly the same way as the original Hafler style.

U1B is actually a straightforward summing amplifier, along with the output consists of all of the info from each the left and appropriate channels. A possibility that springs to thoughts is the fact that we could then subtract the distinction information and facts from this output, to ensure that only material that's definitely typical to each channels will be reproduced. Would this enhance the efficiency for the extent that the added circuitry is warranted? I have a tendency to doubt it, but will appear into this additional.

Centre Channel Control
The pot (VR1) would be to set the centre channel level. This may be a trimpot, or perhaps a standard pot mounted in the rear (to assist stop "fiddlers" from mucking up the settings you like). I've observed circuits which don't involve this, which appears generally a poor concept. When the two channels are summed, the centre channel will ordinarily have a degree of -3dB relative for the left and right channels - supplied the signal isn't mono. Centre channel speech (for instance) will probably be mono, so the level will probably be equal to that of every single from the most important speakers. Given that the centre channel amp and speakers are hardly ever as strong as the primary Left and Right channels, there is certainly a distinct possibility of overload with the amp, the speaker or each.

Due to the fact the centre channel is supposed only to fill the "hole" and offer a stable centre sound image, it will not must be as loud - particularly because it'll practically undoubtedly have inferior sound superior towards the principal speakers and will thus degrade the overall sound excellent. The level manage will permit you to set the level to just adequate to supply the stable sound image, and no much more.

The capacitor (C1) is optional. It gives a nominal 8kHz roll-off frequency (that is apparently rather regular for "real" surround-sound processors). This assists to minimise any disturbance towards the most important stereo signal, but really feel free of charge to leave it out, given that most centre channel speakers almost certainly will not be capable of reproduce considerably above this frequency anyway.

Sub-Woofer Output
The sub-woofer output is merely taken directly from the centre channel mixer, and I integrated no low-pass filter simply because I do not know of any sub which doesn't have a filter already. Adding a different one basically adds unnecessary complexity, and will introduce phase shift in the output that a phase compensation circuit (usually integrated in sub woofers) may possibly not have the ability to cope with.

Miscellaneous
The 100 Ohm resistors inside the outputs are to stop the capacitance in the signal leads causing the opamps to oscillate. At this value, they are going to lead to no high frequency loss, unless you insist on 100m lengthy signal leads (in my expertise, these are uncommon).

It'll also be noticed that you will discover two outputs for the rear speakers, merely in parallel. I integrated this simply because it can be less difficult to wire if the user is connecting a stereo amp for the rear speakers. Naturally, a mono amp will do just fine, so long as it's capable of driving the two rear speakers in parallel. This could not be probable if the speakers are 4 Ohm forms (these are becoming a lot more popular in hi-fi, so its not that silly).

The enhanced Hafler Matrix surround sound decoder circuit source page: http://english.cxem.net/equaliser/equaliser6.php

Low Noise Stereo Preamplifier based NE5533

2011-12-25T15:46:00.000-08:00

This is the circuit diagram for low noise stereo preamplifier based on NE5533 operational amplifier. The circuit uses 2 pieces of NE5533 since there is only 2 op-amp circuits inside NE5533. This circuit is featured volume level, right/left balancing and loudness level adjustment. It will be easy to build this circuit since the components used in this circuit is not much and easy to find at electronic store.

About NE5533:

The NE5533 is dual/stereo high-performance low noise operational amplifiers. Compared to other operational amplifiers, such as TL083, they show better noise performance, improved output drive capability and considerably higher small-signal and power bandwidths. The single op-amp version is NE5534.

This makes the devices especially suitable for application in high quality and professional audio equipment, in instrumentation and control circuits and telephone channel amplifiers. The op amps are internally compensated for gain equal to, or higher than, three. The frequency response can be optimized with an external compensation capacitor for various applications (unity gain amplifier, capacitive load, slew rate, low overshoot, etc.) If very low noise is of prime importance, it is recommended that the 5533A version be used which has guaranteed noise specifications.

Download the NE5533 datasheet here.

22W Audio Amplifier with TDA1554

2011-12-18T20:00:00.000-08:00

Here the 22W audio amplifier which is low cost and very easy to build. You can use this circuit as a booster in a car audio system, an amplifier for satellite speakers in a surround sound or home theater system, or as an amplifier for computer speakers

Circuit Notes

Use 4 ohm speakers for best performance, but 8 ohm units can be used too.
The circuit dissipates roughly 28 watts of heat, so a good heatsink is necessary. The TDA1554 chip should keep cool enough to touch with the proper heatsink installed.
The circuit works at 12 Volts at about 5 Amps at full volume. Lower volumes use less current, and therefore produce less heat on the TDA1554 chip.
Construction on Printed circuit board (PCB) is preferred, but universal solder or perf board will do since the design is very simple. Keep lead length short.

Parts List:
R1 = 39K
C1,C2 = 10uf/25V
C3 = 100uf/25V
C4 = 47uf/25V
C5 = 100nF
C6 = 2200uf/25V
U1 = TDA1554

2 Way Active Speaker with STK4042

2011-11-22T22:14:00.001-08:00

Active speakers have many advantages over the simple speakers using passive materials for implementing the components separation of frequencies. In the case of active speakers have proportionally higher manufacturing costs, since each loudspeaker is driven by its own amplifier. In a properly designed active speaker, the sound quality is much better and very low distortion, because it uses inductors and capacitors in the signal path,. Those capacitors are on the path of the signal have a very small price and very good quality. This does not mean that a well designed passive speaker is good, maybe better than an active. Unlike an active speaker is much more difficult to manufacture.

In [Fig.1], is an active channel speaker 2-way. As shown in the Block diagram [Fig.2], is a classical crossover 2-way crossover fc = 3100HZ -24dB/oct. This frequency was chosen because it is near the crossover of many speakers of trade, but can be changed and customized to your choice of speakers, enough to use the formulas give for the calculation [Fig.3]. The IC1 makes the adjustment input filters around the IC2 create a high pass filter frequency for frequencies above Fc = 3100HZ, contrast material around the IC3 create a katodiavato filter for frequencies below 3100HZ. With the trimmer TR1 in the line of high frequency can be adjustable, if necessary, the level between the two loudspeakers. You will usually need to be lowered by 10% the level of the tweeter than the woofer. In many parts of the filter capacitors and resistors are not used, but it's there for future changes, another crossover as the R6-10 not used.

In the next stage the two outputs of the filter led to two power amplifier in IC4 for high frequencies and IC5 for low. These are two of Sanyo hybrid integrated output 80W/8ohms with very good features and sound. Can be changed to another type of series as STK4036, STK4038, STK4040, with a corresponding modification of power supply. This series is used in many cases active speaker with very good audio results. Good is to use the formula STK4042XI, because it has more modern interior design in relation to the type STK4042II. The filters RLF1-2 at the output of amplifier consisting of the resistor R27 and R38 and a coil wrapped around it in three layers. The coil is made with 25 to 30 turns of copper wire with a diameter of 1mm. In the output amplifiers are the contacts of relay RL1, which is controlled by the DC protection and delay. This circuit is located around the IC6 and works as follows: When the circuit is powered by a tendency there is a delay of 5 sec to connect the speaker outputs on the amps so they do not hear the noises of charging capacitors. Unlike when you stop feeding the circuit then RL1 disconnect quickly the speakers from the amplifiers, so they do not hear the noise discharge of capacitors. While the circuit protects speakers from continuing trends that will occur for any reason, the output of power amplifier , opening the contacts of RL1 and disconnecting very fast loudspeakers.

The circuit protection is evident from Led [D20], which should be placed prominently on the speaker box. The wiring is shown in Fig.2. The AC cord is toroidis good quality. The mainboard, the heatsink, the power transformer, bridge rectifier BR1, as well as all materials that appear outside board mounted on an aluminum block suitable size which adapts to the dimensions of the box and put the speaker on the back of the box. The two amplifiers IC4 and IC5 are screwed onto the back of the heatsink. The overall efficiency of the speaker always depends on the characteristics of units Tweeter and Woofer which used to it, as well as the design and quality of the box. Earliest used in place of the tweeter and woofer T33A B200G of the KEF.

Part List

R1-21-32-25-36-58=1 Kohms	C19-20-52=10uF 25V	IC1=TL071
R2=47 Kohms	C21-35=470pF	IC2-3=TL072-NE5532
R3-4-5-7-8-9-46=22 Kohms	C22-36=470nF 63V MKT	IC4-5=SKT4042[XI] or [II]*See text
R6-10=N.C *See text	C24-25-26-38-39-40=100pF	IC6=4093
R11........18=22 Kohms	C27-41=10pF	IC7=7812T
R19-20=47 ohms	C28-42=100nF 100V MKT	IC8=7815T
R22-33=33 Kohms	C29-43=1nF 63V MKT	IC9=7915T
R23-24-34-35=100 ohms	C30-34-44-48=100uF 63V	RL1=Relay 12V [G2R2 Omron]
R26-37=0.22 ohms 5W	C31-45=220uF 25V	RLF1-2=*See text
R27-38=10 ohms 3W	C32-33-46-47=10uF 63V	F1-2-3-4=1.6A FAST 5X20mm
R28-39=6.8 ohms	C49=47uF 25V	F5=1A SLOW 5X20mm[Fig.2]
R29-40=12 Kohms	C50-51=100nF 63V MKT	T1=220V//A=2X30V 250VA B=2X15V 30VA [Toroidal]
R30-41-53-54=10 Kohms	C53=1uF 25V
R31-45=560 ohms	C54=3.3uF 25V
R44-45=1 Mohms	C55-56-58-59=33uF 63V	JF1=3pin male supply jack
R47=39 Kohms	C57-60=22uF 16V	JF2=Female RCA Jack
R48-50=15 Kohms	C61-62=15000uF 63V AXIAL	J1-3=2pin conn. with 2.54mm pin step
R49-51-52-55=56 Kohms	C63-64=2200uF 25V AXIAL	J2=3pin conn. with 2.54mm pin step
R56-57=3.9 Kohms	C65-66-67-68=100nF 63V MKT	J4=3pin conn. with 3.96mm pin step
R43=470 ohms 1W	Q1=BD679	J5=4pin conn. with 3.96mm pin step
TR1=47 Kohms trimmer horizontal	Q2-3=BC550	T=Tweeter 8ohms 50 until 80W
C1-22-36-23-37=1uF 63V MKT	D1-2-3-4=1N4002	W=Woofer 8ohms 50 until 100W
C2=390pF	D5=8.2V 0.5W Zener	BR1=Bridge rect. 400V 25A [Fig.2]* See text
C3-4-7-8-14-15=100nF 63V MKT	D6=1N4148	BR2=Bridge rect. 100V 1.5A
C5-6-9-10-11-12=3.3nF 63V MKT* See text	D7.....19=1N4148	All resistors is 0.5W 1% metal film except for announce differently
C13-16-17-18=3.3nF 63V MKT*See text	D20=5mm LED [Fig.2]

2 Way Active Speaker with STK4042 source: http://users.otenet.gr/~athsam/2_way_active_loudspeaker_eng.htm

TDA2030 : 15W OTL Audio Amplifier Circuit

2011-11-11T16:33:00.000-08:00

This is the circuit diagram of 15W OTL audio amplifier based single power IC TDA2030.

The TDA2030 is a popular power chip for low power amplifier circuit. The circuit will deliver about 15W audio power when use 8ohm loudspeakers. For maximum power output, you need 24VDC power supply with 1A current, for single/mono channel. Use power supply with 2A minimum output current for stereo channel. Do not forget to mount a heatsink on the IC.

15W OTL Audio Amplifier PCB design

Class-AB Headphone Amplifier Circuit

2011-11-01T04:36:00.000-07:00

This is the circuit diagram of Class-AB headphone amplifier which built using 3 transistors of BC549 and BC559. The circuit is very simple and will give you good audio performance.

The power consumption of this headphone amplifier circuit is claimed to be very low. Two pieces of AA battery will supply the circuit for long time.

Components List:

R1 - 100K
R2 - 330
R3 - 100
R4 - 22 (2 - 4.5V)
R4 - 100 (5 - 12V)
C1 - 4.7uF

C2 - 4.7uFC3 - 100 - 1000uF
C4 - 220uF
P1 - 100K
D1, D2 - 1N4148
Q1, Q2 - BC549
Q3 - BC559

Specifications:
Power Supply Voltage: 2 - 12V
Power Consumption: 10mA/3V - 30mA/12V (measurements taken using a stereo version)
Output Power: 300mW

The circuit can be used for common electronic devices such as radios, CD/DVD Players, computers, audio/video players, ipods etc.

Circuit Source: Class-AB Headphone Amplifier Circuit

60W Class AB Audio Amplifier with TDA7294

2011-10-26T04:39:00.000-07:00

Here is the circuit diagram of 60W class AB audio amplifier which is built based power IC TDA7294. The TDA7294 amplifier module is a monolithic integrated circuit. It's meant for use as an audio class AB amplifier in hi-fi applications. It has a wide voltage range and output current capability, enabling it to supply the highest power into both 4 ohm and 8n ohm loads. Using the addition of a handful of components and also a appropriate power source, this module will achieve 50W RMS into 8-ohm with 0.1% THD.

You have to provide a heavy duty heatsink rated at 1.4°C/W. Pin 10 will be the MUTE input and pin 9 provides you with a STANDBY mode. Muting ought to always take place just before standby mode is used. Connecting these pins permanently to the power supply rail (insert links) makes sure that the amplifier comes on instantly on power up. Extending the time constants R3-C6 and R4-C5 may possibly eliminate any switch-on clicks. The IC has internal thermal protection that causes the mute to cut in at 145°C and switches the amplifier into standby at 150°C. Don't operate the module without having a heatsink. The heatsink tab on the TDA7294 IC is internally connected towards the negative supply rail. When the module is mounted inside an earthed metal enclosure then the IC has to be insulated from the heatsink. If not, the negative supply rail is going to be shorted to ground.

Power Supply for 60W Class AB Audio Amplifier:

30W Class AB Power Amplifier Circuit

2011-10-22T05:12:00.000-07:00

30W Class AB power amplifier circuit diagram using power transistor. Set the above amplifier up by adjust the variable resistor R1 to maximum and R12 to zero. After this set up is done, the activate / turn on the amplifier. Adjust the R1 so that the measured output offset is between 30 and 100mV. Once set, adjust the R12 slowly to achieve a quiescent current of around 120mA. Keep checking the quiescent current as the amplifier heats up as it might change due to voltage drop changes in the output devices because of the heat. The heatsinks should be 0.6K/W or less for two amplifiers.

Power supply circuit for 30W class AB power amplifier:

45W Power Audio Amplifier Circuit with HEXFET

2011-09-25T05:46:00.000-07:00

This is 45W power audio amplifier circuit which built using HEXFET IRF9540 and IRF540. This is a ideal solution for the make a good, low cost power amplifier circuit.

Components List:

R1 = 47K ohm	C1-2-6-7 = 100nF 100V MKT	Q5-6 = IRF9540
R2-12 = 1K ohm	C3-4 = 22uF 25V	Q7-8 = IRF540
R3-4 = 3.3K ohm	C5 = 220pF styroflex	TR1 = 5K ohm trimmer multiturn
R5 = 1.2K ohm	C8-9 = 4700uF 63V	TR2 = 1K ohm trimmer multiturn
R6 = [1.2K ohm] 820 ohm *See text	C10 = 1uF 100V MKT	F1-2 = fuse 3A
R7 = 270 ohm	D1-2 = 15V 0.5W zener	J1 = 2pin connector 2.54mm step
R8 = 220 ohm	IC1 = LF411orAD711or LF351	J2 = 5pin connector 5mm step
R9 = 27K ohm	Q1 = BC550C
R10-11 = 22K ohm	Q2 = BC560C	All Resistors 1/4W 1% metal film
R13-14-15-16 = 150 ohm	Q3-4 = BC547B

The preamplifier and the driver support in a operational amplifier [IC1]. The voltage fall in resistors R5 and TR2/R6, drive the output FET's gates and is proportional with the input signal level. Transistors Q1-2 function as voltage stabilizers in the supply lines, but ensure also the essential voltage fall, because the IC1 it should not they are supplied with voltage bigger ± 18V. The consumption of all types that can be used in the place of IC1, are 2 mA, this it means voltage fall in terminal the R5 and TR2/R6 equal with the 2.4 until 2.6Volts. The current regulation it become from transistors Q3-4 in Wilson connection and the current adjustment of bias it becomes from the multiturn TR1 trimmer.

Detailed information about this 45W power audio amplifier circuit with HEXFET:
http://users.otenet.gr/~athsam/power_amplifier_45w_hexfet_eng.htm