Theremin World Recent Forum Posts

Early electronic music before 1945 Substack site with extensive theremin history (by ghost elektron)

Thanks DreadVox and JPascal,

My research on electronic music pre-1945 and Theremin style devices moves beyond Termen's time in Germany, and I'm most interested in the 1928-1934 period. There was a lot of activity involving Thereminists who were trained at the Berlin Theremin laboratory/School of Electrical Music, and who then performed across Europe until 1930 - and elsewhere until the early 1940s 1941. The two most interesting figures were Evgeny Henkin and Martin Taubmann who I have extensively researched and written about on the Song of the Atom Substack publication. Most things written about Taubmann in the past were totally incorrect. I aim to publish more material on these topics soon, though I have written quite a lot already ...

Thanks for your interest in Song of the Atom! I aim to only publish material where I can add new information to the various histories that are already out there.

Building a theremin for a robot voice (by josh craig)

Theremins use oscillators and filters to make their sound. Changing the way you control the theremin turns it into another synthesizer.

Much of the sound of the theremin comes from the way your body directly interacts with the circuit via the electromagnetic field which gives it the organic and hyper expressive quality that seems part-biological and part-mechanical.

I believe this blend is something many people creating a voice for a robot strive for. Ben Burtt achieved this with R2-D2 by vocalizing into different patches on an ARP 2600.

I think your best bet of achieving a theremin-like quality is having a small stylophone on your controller that interacts with an oscillator inside the robot. It won’t sound as organic or unruly as a theremin can, but as far as physical logistics go, it’ll probably be the right design choice.

Etherwave Pitch Antenna wont stay up. (by josh craig)

That was a fast reply! Thank you so much. I’ll go with epoxy.

Etherwave Pitch Antenna wont stay up. (by dewster)

"Etherwave Pitch Antenna wont stay up." Oh, that must make you unpopular with the ladies!

For the EW kit IIRC they recommended epoxy on the threads into the side cheek.

Etherwave Pitch Antenna wont stay up. (by Josh Craig)

I have an older Plus model, and it seems the hole in the wood is slightly too big. I can get it to balance upright but even wind will sometimes knock it over.

I’ve been thinking about filling the threads with wood glue, but I don’t have much experience working on theremins, so I thought it best to see what people on here think. I’m curious if anyone else has run into this issue and might have a fix for it.

Anyway, thanks for all the help in advance!

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

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

Encoder RC Filtering (again)

Revisiting this subject (see previous [LINK]). I somehow got it in my thick head that the circuit specified by the rotary encoder datasheet severely limited the top rotation speed tracking. Here is the circuit, R1=R2=10k, C=0.01uF:

Note that at switch closure the switch will see inrush current through R1||R2 which for the datasheet circuit would be 5k. This gives 0.66mA for a 3.3V supply. Over a short period of time this ramps down to half of that, or 0.33mA as C discharges. The difference in resistance to VCC as seen by the capacitor means that the rise time will be half of that of the fall time, and this is a good feature, as grounding is a less ambiguous state, and any bounce or noise at closure should be slowed more so as to reduce the amplitude of these false rising edges.

I measured the FPGA internal pull-up strength on my lab unit and it took around 20k to pull it to VCC/2. The encoders on my lab unit are still going strong after all these years, so I don't think I want to lower the impedance here too much and possibly speed up their wear with excessive current. We don't want to make things too high impedance though, as this might let the FPGA input pin float around, and this in the presence of rather strong electric fields that the Theremin can generate. The ~20k internal pull-up has been working fine, and without the use of C to attenuate AC at the pin. Coincidentally, this is almost identical to the series connection of R1 and R2 = 20k, which is the effective pull-up when the switch is open.

The fastest I can spin an encoder with the kit knob on it produces a detent cycle of 2ms, which is a 500Hz square wave coming out of the encoder outputs. Since 2 * pi * freq = 1 / RC, if we solve for C given R=20k we get C=0.032uF. Upping the cutoff by 3x so that the edges aren't too rounded off gives us 0.01uF, or the datasheet C.

To test the datasheet circuit on the bench, I unplugged the left bank of encoders and attached three of the pins to an encoder with the associated filtering circuitry mounted on a breadboard. To swamp the effect of the internal FPGA pullup, I lowered the filter impedances by a factor of 5, so R1=R2=2k, C=0.05uF. Here's an image of the voltages at the FPGA pins with me spinning the endcoder really fast:

So, I know that I'll be using the datasheet circuit, with the final component values the same as, or close to, those specified. The scope images look good to me and the filtering has no influence over how fast the encoder is spun. I'll also be including ESD protection TVS diodes at the encoder pins to ground, and all of these new components will reside on the encoder PCB.

Damaged Ferrite Cores for L11 and L6 - Can you swap cores from SLOT TEN 5-11s? (by clplibrary)

Did not see this post until now:

http://www.thereminworld.com/Forums/T/33994/moog-etherwave-restoration

Those are still available, albeit in a much larger quantity than what I need. My original questions seems a bit ridiculous now. I was operating under the assumption that finding a substitute for the 5-10s was no longer optional, and that any new inductors would require additional modification.

Damaged Ferrite Cores for L11 and L6 - Can you swap cores from SLOT TEN 5-11s? (by clplibrary)

Hello Theremin World,

Here's some background info on me (skip past to get to my question):

My name is Kevin. I am a Library Services Associate for the Carnegie Library of Pittsburgh. I work in the Music Department of the Main Branch, where I help manage the Musical Instrument Lending Library.

Some background information on this collection:

Founded in 2017
Enjoyed by patrons of all ages
Around 70 items currently in circulation
Permanent display table at our Main Branch features larger, more expensive items, including:

Moog Etherwave Plus Theremin
Pittsburgh Modular Lifeforms Foundation Evo
Custom Serge Modular Synthesizer
Moog Model D

So far in this role I have had to make minor repairs to some equipment: re-soldering loose connections, applying DeoxIT spray, updating firmwares, etc. Our Etherwave Plus was damaged recently when a patron knocked the pitch antenna loose, disconnecting the antenna wire and damaging that joint of the box. I re-soldered that wire and re-glued that side of the box. I then attempted to adjust the tunable inductors of L11 and L6 (I did not touch L5). I did this with a metal hex screw driver, and immediately damaged both cores. I realize how foolish this was. I was simply too impatient to order a proper tuning tool (ours was nowhere to be found when I started and I was reluctant to spend my own money to order another :getlost.

I spent a few hours yesterday researching the Coilcraft SLOT TEN 5-10 inductors I damaged, including reading through dozens of posts on this site. I apologize to the regulars of this forum for contributing yet another post on this topic. Unsurprising to you all, the 5-10s appear to be all gone. I reached out to Coilcraft to see if they had anymore and they replied soon after that they have none left. I was unable to find them listed anywhere else online. I did find a listing for some 5-11s. I am wondering if it is possible to swap the ferrite cores from those for the damaged cores in the 5-10s in our Etherwave. I have read about radio enthusiasts doing this for RF inductors but could not find an example of this repair for the variable inductors in theremins.

For now I have replaced our Etherwave Plus with one of our Moog Theremini's that are available for checkout. It's a fine substitute, perhaps more kid friendly with the digital fx, but it doesn't have the presence of an Etherwave. Also it takes one item out of circulation. We have a Big Briar Etherwave in our offices as well. I thought about substituting this but it does not have a headphone out. Also there is no power indication light, which one of our patrons who has a pacemaker looks out for when entering that part of the building.

Anyway, thank you for reading. I promise I tried to do my research before posting. I am truly grateful for this forum as a resource. Any response is greatly appreciated. Our Etherwave is the most popular instrument we have here at the library. Dozens of patrons use it every week. I'll do whatever I reasonably can to fix it.

Best,

Kevin

Love to get a Claravox that Someone Doesn’t Want (by Trymeinchesss)

I wish I could help but I only have a theremini (Which I don’t really want myself lol) Music instruments become such a large part of you and it would be so hard to lose them.

Love to get a Claravox that Someone Doesn’t Want (by Yngvox Moogsteen reborn)

I had many sounds developed on the Claravox I liked. I saved the app and sounds hoping I acquire a Claravox again. I know it had many limitations but I really liked it and miss it. I don’t have means for Etherwave pro and not sure I could assemble a D-Lev from kit. I programmed computers but not for 40 years. Love electronics but haven’t done much soldering. From videos the D-Lev looks really exciting. Hope I can find one made by one of the people who made many of the cool ones I have seen on Theremin World.
Sorry to digress, I know many people on this site hated their Claravox. Please let your Claravox find a home where it will be Loved and played often.
Thanks everyone
Play music Every Day for a happy Life.

Yngvox Moogsteen

Let's Design and Build a (mostly) Digital Theremin! (by Yngvox Moogsteen reborn)

Thank you very much. I have a new power supply I have to find. I will get a hold of you soon. I also have antennas from Claravox, could they be used on D-lev.
Really appreciate anything you do.
Thanks again….

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

"I would like to send my fire damaged etherwave to you Dewster ,to see if it’s repairable." - Yngvox Moogsteen reborn

OK, email me and we'll arrange for shipment. My contact info is on the support page: https://d-lev.com/support.html

Love to get a Claravox that Someone Doesn’t Want (by Yngvox Moogsteen reborn )

Hi. This is Yngvox. Had a fire and lost a Claravox, Etherwaveplus, and Burns all in one room.
I had many other instruments in a separate area,I would love to trade for Claravox. I have mostly guitars. Also some very nice museum quality art. Any other theremin would be considered for trade. Really miss my Claravox.
Also lost cello, viola, strat, lots of harmonicas, keyboard,Korg synthesizer , sheet music, Fender base6, a few other things. A 4 Track and 24 Track recorder, amps. Etc. Etc.. Much of Fifty years of collecting gone but saved a lot of guitars. Probably had too much stuff. Know my priorities better now. Would still like a Cello,a keyboard and a few harmonicas some day.

Doing really well now. Anyone wanting to make any trades, let me know.
Thanks

ps. I had trouble getting my password recovered after IPad lost in fire with password on it for my original account so I remade this one.

Thanks again
Everyone take it easy.

Let's Design and Build a (mostly) Digital Theremin! (by Yngvox Moogsteen reborn )

I hope there is a way to expand production of the D-Lev. It would be wonderful if more people could be exposed to a great theremin at an affordable price. The way a theremin connects you to sound has no comparison. It forces you to listen. Good luck Dewster and all the Theremin experts on Theremin World. Jason started something important and I hope it continues. I learn with each post.
I lost a Claravox, Burns,Etherwaveplus in fire.The only Theremin I have been able to acquire is the new Etherwave. So far I don’t like the sound as much as the Etherwaveplus and would like a more gradual Volume control. May recalibrate. Any hints on removing top plastic cover. New Etherwave does seem better at note linearity.
Thanks again,
Yngvox

Let's Design and Build a (mostly) Digital Theremin! (by Yngvox Moogsteen reborn)

I am back.

Someday hope to try a D-Lev. I had to start anew as I can’t reset password. I have missed being able to comment for a while. Wish everyone well. I would like to send my fire damaged etherwave to you Dewster ,to see if it’s repairable. Anyone with a Claravox they don’t like trade me for a guitar or two. The guitars were safe from fire.
Thanks
Everyone have a great day…

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

Anti-Lock Brakes

For the past few days I've been working on an FPGA feature that allows the software to monitor and influence the pitch and volume field DPLLs. As discussed in the Square Deal post, there are problematic locking situations associated with the strong harmonics of square wave coil drive, and it would be highly desirable if these could be addressed on the fly. Having any fix rely on software means we can hopefully address any issues in the future with just a software update, rather than an FPGA pump (which requires an Altera programming dongle and is quite fiddly to do).

The DPLL inputs from the AFE are "zero" (in-phase) and "quad" (quadrature). The coil has 90 degrees of delay at resonance, and the DPLL attempts to maintain this phase relationship by automatically adjusting the frequency of the NCO driving the coil. The inputs feed an xor construct which functions as a phase detector, so the actual input assignments aren't important to proper functioning - you can actually swap them and nothing bad happens.

As a first pass, I made some logic that counted the rising and falling edges of the quad input, using the rising edge of the zero input to pass that count on and zero it out for the next accumulation. This didn't work well because the zero and quad inputs were electrically swapped on the schematic. I could have just swapped them in the code again, but that's a kludge. Instead, I used the internal drive signal rising edge to count the AFE xor result. This works much better and is immune to input swaps. I decided to make the counters 8 bits wide and non-saturating, because I felt 8 bits was wide enough to catch most error scenarios. When functioning with a proper lock the count should be 4, and a count of 8 generally indicates a bad lock state.

To the phase detector I added two input bits, one to increment the phase accumulator, and one to decrement it. When both bits are active high no accumulation happens, and this mode can be used to unlock and freeze the DPLL for possible lab / diagnostic purposes.

In order to pipe the two 8 bit counts and two sets of control bits to the software, I created a new internal Hive register at address 0xf. Next I wrote a bit of software on thread 5 that gets called at the 48kHz PWM rate (approx. every 20us) which is more than sufficient in terms of response to the SRF bad lock condition. My plan was to differentiate harmonic locking from SRF locking via the pitch and volume frequency registers, but this proved to be unnecessary. First I would touch the plate to initiate an SRF lock, and have the software apply a decrement to the DPLL if the edge count was over 4. This didn't work at all and led to a bunch of other bad lock scenarios. Next I tried applying an increment when the count was over 4 and this worked like a champ, quickly clearing the SRF lock and establishing the proper quadrature lock. It's not entirely clear to me why decrementing fails so badly, but I should probably figure this out before I release the design.

You're playing with fire any time you're trying to outsmart a control feedback loop with software monitoring. I'll probably add an error byte memory location somewhere in the software, and use the librarian to peek and see if any override events have occurred since power-up. We'll see if the monitoring HW or SW need to be a bit fancier to avoid any obvious glitching during normal play.

Anyway, I understand the phase detector DDR integration better, and took this opportunity to remove some confusing (though generally moot) states from it, as well as the non-DDR build option from both it and the NCO. The SystemVerilog code is much clearer now.

[EDIT] And, as usual, this is a feature I should have implemented a million years ago (someone put this on my gravestone).

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

Sorry for the late reply. Yes, please add me to your interested/ ready to purchase list, that would be awesome. I'll send a more formal request to the email you provided. Thanks again, I really appreciate your time and response.

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

"Apparently they all have issues, (especially the clairvox) I've been looking for an eitherwave pro for a while, searching online and came across your D-lev build. Are they available to purchase or is it possible to purchase the kit?" - Silverleaves

At this point the D-Lev is more of a project than a product, and after making and deploying 50 kits into the field, things reached the point where a re-design felt necessary, both to improve things somewhat, and also to reduce the manual manufacturing effort. I plan (i.e. hope) to make more kits in 2026, but I can't really promise anything in terms of timeline. I'm just one guy doing R&D, soldering, and 3D printing. It's more of a hobby really, that's taken on something of a life of its own.

I maintain an "interested" list, do you want to be included on it? If so, please email me (my email address is on the D-Lev support page: https://d-lev.com/support.html). I should warn you that the list carries with it no guarantees, and the list is getting rather long.

If you have any questions I'd be happy to answer them. I often do Zoom meet-and-greet / show-and-tell sessions. Let me know if you're interested in something like that, it's always great to chat with Thereminists and other enthusiasts!

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

"Thanks and gratulations to Eric for this great step." - JPascal

Thank you Jean, that means a lot coming from a fellow Theremin designer!