Theremin World Recent Forum Posts

The End Is Near? (by André)

I just received an email from Thereminworld Patreon site.

It says that I am a free subscriber and proposes to upgrade to a paid membership.

I guess this is an automatic email. It's in french.

Jason, are you still with us?

Let's Design and Build a (mostly) Digital Theremin! (by dewster)

Full Metal Hot End (Let The Filament Flow)

I like my Ender 3, but of course it has been somewhat necessarily modified (notably a new controller board & magnetic textured print bed which should have been standard equipment IMO). Previously the filament feed motor was moved from the chassis to the X axis, making it more of a direct feed than a Teflon Bowden tube type. While this was in many ways an improvement due to reduced retraction and stringing, the remaining short length of Teflon tubing still went all the way to the print nozzle, and over time the tube would degrade with heat, necessitating replacement. It's kinda tricky to know when the tube is at fault, so you end up replacing any time prints start looking bedraggled. One can purchase full metal hot ends, but I was unaware until shopping on-line that one could also just replace the feeder tube with an all metal version at a much lower cost. I got this on Amazon for $12 USD and some change (https://www.amazon.com/dp/B0971FNCM4):

I installed it and did a print. Afterward I noticed that there was a lot of leakage at the top of the aluminum heat block, and the nozzle was at a funny angle. Turns out the block threads on the nozzle side were stripped, which is something that just happens when you have to periodically replace the Teflon tube. Looking around on Amazon, I found this brass version for $9 USD, which comes with a new rubber boot (https://www.amazon.com/dp/B0CLD54CYF):

I very carefully moved the thermocouple and heater element over to the new block, using Creality thermal grease for both. I also put some grease on the metal feeder tube. Afterward I heated it up to operating temperature (240C) and re-tightened everything. The PID adjustment was built-in to the software, so that was pretty quick and painless.

So, one more mod, and hopefully I'll never have to mess with the stupid Teflon tube again. Since the filament has much more contact with the hot end it may be able to print better with larger nozzles and higher flow rates (it's all about the flow).

Open Theremin V4 with MIDI (by dewster)

Surge XT is a pretty nice synth and works great in Linux - thanks for turning me on to that too!

Open Theremin V4 with MIDI (by Mr_Dham)

"And I limited the range to [-120:31] since [-127:-120] aren't really MIDI CC commands (the spec says they are "channel mode messages")" - Dewster

Yes, it is probably the best option. You certainly don't want to send a channel mode messages each time you move the left hand (synth reactions would get pretty messy) and it keeps bit depth.

The preset for reproducing my short video with Surge XT would be as follows: MIDI Bend = 48, MIDI Channel = 2, MIDI CC = -120 (aftertouch)
(Most Surge XT presets use aftertouch)

Open Theremin V4 with MIDI (by dewster)

Thanks for clarifying those points Vincent!

"If you want to implement it on the D-Lev, as you have the knee, maybe you could treat it just like a CC and allow the user to chose etheir a CC or the aftertouch for the volume hand." - Mr_Dham

Excellent idea! I relabeled the MIDI:cc knob to "vcc" since it is volume field related. And I limited the range to [-120:31] since [-127:-120] aren't really MIDI CC commands (the spec says they are "channel mode messages"). It only took 5 extra assembly instructions to make MIDI:cc[-120] do aftertouch. MIDI:cloc sets the aftertouch onset point in the volume field as it normally does for CC.

Open Theremin V4 with MIDI (by Mr_Dham)

Legato determines whether or not to trigger a new note when the pitch bend range limit is exceeded.
(e.g. "Legato = Not Activated and PB = Not Activated" corresponds to "MIDI bend = 0" in the D-LEV)

Aftertouch:
Yes, you first hear the note and then an extra gesture (pressure on the keyboard) allows you to control something.

In the Open Theremin the volume is internally à 8 bit value and I need a 7 Bit value for MIDI. For CC, I divide this value by 2. For aftertouch, I use the 128 to 255 range (upper range) transposed into 0 to 127. The effect is somewhat like the knee of the D-Lev.

If you want to implement it on the D-Lev, as you have the knee, maybe you could treat it just like a CC and allow the user to chose etheir a CC or the aftertouch for the volume hand.

Aftertouch message is a two bytes message: Dn_H, 0vvvvvvv_B where n is the channel (0 to F) and vvvvvvvv is the value (0 to 127). It saves 1 byte compared to CC, probably to save some CPU load within high priority task of sound generation in 1980's synths.

Open Theremin V4 with MIDI (by dewster)

"... I also added a way to control Mono Aftertouch with volume antenna..." - Mr_Dham

You sir are a MIDI master! Thanks for the explanation!

The only thing I don't understand in your quick guide is the pitchbend / legato / aftertouch knob. It can turn PB off yielding a quantized pitch field and, as you say, aftertouch applies to the volume field. But I'm unclear on what legato does?

[EDIT] Also, for a keyboard anyway, aftertouch is extra pressure after the key is played. How does aftertouch work in your new SW load?

Open Theremin V4 with MIDI (by Mr_Dham)

By the way I also added a way to control Mono Aftertouch with volume antenna and a way to save a custom startup configuration.

Open Theremin V4 with MIDI (by Mr_Dham)

Hi Eric,

I had an inquiry to make the D-Lev more MPE compatible, but MPE was implemented for polyphonic controllers, and since the Theremin is monophonic I couldn't see what the benefit might be?

I received the same inquiry... and had same reaction initially.

In fact, any monophonic controler is already MPE compatible provided that you can extend pitch bend range to 48 and choose the MIDI channel. Then, good news, the D-LEV is already compatible and any version of the Open Theremin as well.

To sum up, MPE consist in having a Master Channel receiving what is common to all note played (Ch. 1 or Ch. 16) and a given number of Member Channels (from Ch2 to Ch15) to distribute what is specific to each polyphonic note played. Pitch bend range is by default equal to 2 on Master Channel (pitch wheel management) and equal to 48 on Member channels (glissando management). There are three standard gesture axis : x= Pitch Bend, y=CC 74 and z=Mono Aftertouch but this is mostly a matter of terminology and has no real impact...

Initially based on a non MPE implementation, Open Theremin had its default pitch bend range set to 2 and default Channel setting set to 1. This was resulting in a quite frustrating glissando where there was note transition every 2 semitones. Added to that classical synth (HW or SW) have there PB range not that much expandable (sometime one octave max).

If you have a MPE synth, (e.g. Surge XT in MPE mode), PB range will be of 48 on all channels from Ch2 to Ch 15 by default. As Theremin is monophonic, choosing Channel 2 and a pitch bend range of 48 will make your theremin address properly this MPE synth, enabling the user to make long glissando on 4 octaves.

Having the proper MIDI setting configuration on hand gives a plug and play user experience on an MPE synth.

For the D-LEV, the only thing you need to do is to create a preset (e.g. 211 "MPE_Ctrl") with : MIDI bend = 48, MIDI Chan = 2, MIDI CC = 74.

On the Open Theremin there is no preset, then I can only rely on default startup configuration to provide a good user experience. I found with MPE synth the 1rst user experience that I was searching for.

Before: Typical first user experience with a classical synth and PB range = 2
After: Typical first user experience with a MPE synth and PB range = 48

Long story short, it is just a mater of setting. But I remember that a wise man told me that synths live and die because of their presets ;-)

Open Theremin V4 with MIDI (by dewster)

Thanks Vincent! This might be a dumb question, but what makes it MPE specifically? I had an inquiry to make the D-Lev more MPE compatible, but MPE was implemented for polyphonic controllers, and since the Theremin is monophonic I couldn't see what the benefit might be? I'm not attacking what you're doing here, quite the contrary. I'm genuinely curious!

Open Theremin V4 with MIDI (by Mr_Dham)

Hi,

Some news about Open Theremin V4 with MIDI.

I am about to deliver a new version 2.0 of the MIDI software
It is currently in its development branch.

It is purposed to provide a good first user experience paired with synths like Surge XT thanks to an increased MPE compatibility.
It also provides the possibity to save settings in EEPROM so as favourite config persists after power off.

You can check it out here : https://github.com/MrDham/OpenTheremin_V4_with_MIDI/tree/MPE_compatibility

Maybe note these two breaking changes:
1- Loop antenna MIDI CC 8 positions are now : None, 1-Modulation, 2-breath, 4-Pedal, 7-Volume, 11-Expression, 71-Resonnance, 74-Cutoff (More "musical gesture" oriented than "effect control")

2- Default startup configuration is plug and play with MPE synths :
Register = Center , Timbre = 1st Waveform, Channel = MIDI Channel 2, Note Lifecycle = Aftertouch on/Legato on/Pitch Bend on, Pitch bend range = 48 Semitones, Volume trigger = 0, Rod antenna MIDI CC = None, Loop antenna MIDI CC = 7-Volume.

31250 MIDI baudrate is selected by default in the code to avoid disturbing people having a MIDI DIN connector. (Probably main MIDI installed base).

I also made a video of what it should give after downloading the software and connecting it to Surge XT.

There is a quick guide (use this link, the link in the readme will work when it is merged in main branch)

It is being beta tested. If it is OK, I'll merge the feature branch to my main branch and publish a version.

When was the linearizing coil introduced? (by JPascal)

Found this in The Electrical Experimenter Magazin 1916.

Only Getting ~80Hz Range on Pitch Antenna - Circuit Issue or Room Issue? (by JPascal)

Significant progress has been made. I recall that the sound in the video—which was briefly visible and showed the lab and a colleague in the background—was clear and had some overtones. However, the frequency range of 20 Hz to 400 Hz is still too low; you need 1.5 to 3 kHz to get in "distance linearity" more octaves (doubling the frequency results in one octave). I assume that the antenna-high-inductance circuit is not yet the main oscillator. As mentioned above, this can be verified.

Only Getting ~80Hz Range on Pitch Antenna - Circuit Issue or Room Issue? (by scrapwiz)

Hello all! I don't currently have access to my build, but I'll try to post a video later today. The low, raspy sound is gone, the sound is much cleaner, and the frequency now smoothly transitions to the zero beat through the lower octaves.

What I did, in chronological order:
1. Added JFET follower stages (did not seem to have a big impact)
2. Previously had both oscillators power and ground rails directly connected; disconnected them and added a small RC filter at the connection between each and the +12V/GND rails (I think this had a small effect, but there was still locking)
3. Physically moved the oscillators about a breadboard's length apart (this fixed the locking entirely)

I also had a small issue where my JFET followers seemed to "drift" from a full 400mVpp amplitude to practically zero. Do not make the same mistake as me... the gate on your JFET needs a resistor to ground (which seems very obvious in retrospect, but it was a big system!)

I was not really expecting physical distance to have such a big effect on the inductor interactions (something something inverse square law). I kind of thought people were exaggerating the effect, but no, it's like 400Hz minimum frequency down to like 20Hz.

ILYA, this is my exact shopping list:
- 10mH inductors: https://www.digikey.com/en/products/detail/epcos-tdk-electronics/B82144B1106J000/3501400
- 1mH inductors: https://www.digikey.com/en/products/detail/bourns-inc/RL181S-102J-RC/946948
- Capacitors and resistors I just took whatever I found, seems to work fairly well

Moog Etherwave antenna (pitch) (by ggaspari1)

Hi I'm hoping to locate and buy a pitch antenna for a Moog Etherwave. If anyone can help point me to the right place I would be most appreciative. Thanks!

What if I can’t afford an oscilloscope? (+Variable inductor issues) (by xcott)

I uploaded a video to Youtube show what I mean (apologies, I don't know how to embed):

https://www.youtube.com/shorts/iZFlkCFLcoI

The very first frame of the video shows the variable oscillator breadboard with jumpered inductors, the orange wires being the jumpers. They're 47/22/15/10/4.7/2.2/1uH. I ended up jumpering the 10 and 2.2 to oscillate at 300kHz.

The range is large because at time of recording we hadn't yet adjusted the fixed pitch oscillator. We also have to re-do it to make it as tidy as the variable oscillator breadboard. Already super happy with the range of the thing, however.

Also also, the scope in the video is one that we snagged from a storage room before it went to e-waste, so I guess the video is a demonstration of that also.

What if I can’t afford an oscilloscope? (+Variable inductor issues) (by xcott)

Late to this thread, but I work at a university, and they can't get rid of old scopes fast enough. We have a storage room full of them, and the next time we get an infusion of new scopes for the teaching labs we'll be struggling to find a use for the current ones. I'm not talking about ancient scopes from the 80s, but DSOs that are way more than capable of handling what you need for building a Theremin.

Thus I recommend you reach out to a local college, university or community college and ask if they have any older scopes taking up dust that you can at least borrow, that they might have been planning to send to e-waste. You might just get lucky.

Regarding the variable inductor, I have a student building a Theremin from the Etherwave schematic and we were unable to find 47uH variable inductors. Instead we used a trick that is commonly used in amateur radio auto-tuners: we just put 6-7 fixed inductors in series on a breadboard spaced well apart, each inductance twice the previous one (values commonly available in inductor assortments,) and then we plug in wire jumpers to bypass whichever inductors we want in order to select the variable inductance in "binary". This is nice because it's cheap, because you can reliably go back to a previously chosen inductance, because you don't touch or budge the actual inductors while performance the adjustment, and because using the jumpers you can adjust the oscillator while it's running without breaking the tank circuit.

Trouble Hearing Theremin on Zoom (by André)

I had a similar experience although I have a different interface and a Windows PC.

My mixer/interface is a Zoom Livetrak L6 which has 32 bit ADC's also. (Zoom is the interface manufacturer. Nothing to do with Zoom meeting!)

Trying to use the interface with Zoom meeting in 32 bit mode, I had a very bad and weak sound.
In fact the sound was bad for the other Zoom participants but I could hear them perfectly through the interface.
I switched the interface to 24 bit mode and everything is now perfect both ways.

If your interface allows 24 bit mode, give it a try.

Only Getting ~80Hz Range on Pitch Antenna - Circuit Issue or Room Issue? (by dewster)

"... this low, raspy sound at low frequencies, which might be unregulated power supply? No idea." scrapwiz

I'd bet that's mains hum intermodulation. Please post a short MP3 of it somewhere for analysis.

Only Getting ~80Hz Range on Pitch Antenna - Circuit Issue or Room Issue? (by ILYA)

again,
and what type are they?