Theremin World Recent Forum Posts

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?

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

I used the 1mH coils for the LC tank. I did also use 10mHs in series for linearization like it says in the schematic (with an SRF of I think 2.0MHz or so?) sorry for the ambiguity

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

Bourns RL181S-102J-RC

Are you sure? The "102J" code denotes an inductance of 1 mH. But according to the schematic, 10 mH is required.

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

Hi everyone! Thanks for all the input. Sorry I always end up responding a few days late, but since this forum has been integral to me building this thing I figure I owe it a report afterward xD

JPascal: Indeed it is a circuits lab, but this is not a group project. I just wanted to build an analog theremin
Dewster: Good call on the insulation. I ended up soldering them on protoboards/stripboards (whatever the ones with the connected TH holes are called)
ILYA: Not sure on the resistances, the coils installed are Bourns RL181S-102J-RC

In summary, I have had a very long and arduous journey trying to replicate this build: http://www.thereminworld.com/Article/14695/a-diy-wine-box-theremin. The comments mention the LC filter after the volume antenna is incorrect (it is) but I also could not get the pitch oscillators to go above ~160kHz, which was giving me a horrible pitch field of like 300Hz. I found out the LC tank was resonating with the emitter capacitor as well (which I thought was just a bypass) and the feedback cap was way too high. These values give me a pretty good pitch field:

270pF capacitor for feedback
1nF capacitor for emitter to ground
~100pF capacitor for variable pitch, and about ~40pF + a variable cap for reference pitch

Maybe I'll make my own post after how much suffering this thing has caused me. Currently my biggest problems are bad soldering, the oscillators locking at low frequencies (I really need to add buffer stages between the oscillators and the mixer) and this low, raspy sound at low frequencies, which might be unregulated power supply? No idea.

Again, thank you all for your infinite patience. Some keywords in case anyone who needs this in the future can find it: Jason, 2013, wine box theremin, frequency too low, SRF

Moog Etherwave Plus for sale (US West Coast) (by suntikempatd)

Suntik4d platform digital terbaik dan ter- viral 2026!

When was the linearizing coil introduced? (by JPascal)

"Without this was a frequency change of some kHz by hand-capacitance with the early tube technique not possible."- JPascal This is a bit of a surprise to me, though I'm not a tube guy. What is the limiting technology here? - dewster

I’m not particularly familiar with the early triodes from the 1920th. However, there are some limitations when using Hartley, Coolpitch, or Meissner oscillators with the low capacitances required for a theremin. These are:
- a transconductance below 1, typically 0.5 mA/V;
- low gain and thus strong feedback to compensate for losses; and a grid leakage current.

Most important, however I meen, were the high capacitances between the grid and anode, as well as between the grid and cathode. The were further enhanced by the so called Miller effect. Thus, good stability was achieved for an oscillator in the 300-kHz range using capacitors of a few hundred pF.

Because of Lev Termen found the for audio useful hand capacitance effect of the beat oszillations accidently while investigate the conditions for wide distance and approximation sensors it is near to assume, that there were high inductiv lengthen coils in use, which were coupled with a stable oscillator design.

When was the linearizing coil introduced? (by dewster)

"Without this was a frequency change of some kHz by hand-capacitance with the early tube technique not possible."- JPascal

This is a bit of a surprise to me, though I'm not a tube guy. What is the limiting technology here?

When was the linearizing coil introduced? (by JPascal)

This documents are indeed очень интересно, thank to ILYA.

I suspect, because of the principle of an lengthen coil for oszillators and antennas was always known that time, Lev Termen used it from the beginning of his invention. Without this was a frequency change of some kHz by hand-capacitance with the early tube technique not possible. And without this possibility the instrument not of interest for anyone.

Trouble Hearing Theremin on Zoom (by joshcc)

So, I have been having issues with Zoom on my Mac Book. I have tried all manner of setting in zoom and with my computer. but I cannot hear my theremin.

When Original Sound for Musicians is on, and high fidelity is on it can sometimes be heard, but any sustained note will be cut off. This happens direct input and when playing through a speaker with microphone.

I’m wondering if anyone has run into this issue before at all.

For reference, I have an Etherwave Plus and an SSL 2+ mkii interface, Roland ts and xlr cables, and a Yamaha Hs5 speaker. When I use a mic it’s a sennheiser e835.

When was the linearizing coil introduced? (by ILYA)

"I no longer remember"

It seems it was the official website of Rospatent (the Russian Federal Service for Intellectual Property).
However, it now only displays a reference to the patent, without its full text:
https://www1.fips.ru/iiss/document.xhtml?faces-redirect=true&id=f10c1586e56c930be35eaef170880d19#

When was the linearizing coil introduced? (by ILYA)

I've uploaded the Russian version here (SU890rus.pdf).

I no longer remember where I downloaded it from. There used to be an excellent website, trmvox.ru, hosting a vast collection of documents and articles from various magazines. I managed to download quite a few of them before it went down.

Please note that in many publications about Lev Termen (Theremin), this patent is incorrectly cited as №780.

Here (SU890eng.pdf) is the machine translation into English.

When was the linearizing coil introduced? (by dewster)

"US1661058A (USA, filing date 12/05/1925) – oscillator without a linearizing coil." - ILYA

Oh, so interesting to read that, thanks ILYA! In it he's aiming for 500kHz to keep it out of the AM band, I'm going for 450kHz for similar reasons. He also refers to the field as "electrostatic" which I feel is a misnomer since the field is AC. It also seems he's buffering the oscillators before mixing, shades of the ESPE01? Also mentioned are multiple pitch antennas for a polyphonic instrument.

I wish I could shed some light on when the linearizing coil was introduced, but I got nothing. I'm guessing he sensed the non-linearity of the near field and decided a double resonance might help ameliorate it to some degree, and went down that path. It seems he's almost part of the way there with the transformer coupling to the antenna. I agree that it probably deserves a patent of its own.

How does one view SU890? I couldn't find it.

When was the linearizing coil introduced? (by ILYA)

Looking at the patents:

SU890 (Russia, filing date 06/23/1921) – oscillator without a linearizing coil,
US1661058A (USA, filing date 12/05/1925) – oscillator without a linearizing coil.

In RCA and custom theremins for Clara and Lucie, the linearizing coil is already present.

It would be interesting to know when and under what circumstances Lev Thermen came up with this idea. In principle, it seems to merit its own separate patent.

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

Check the resistance between the antenna and the transistor collector using a multimeter (i.e., verify the continuity of the coils and the wire-to-antenna contact). The reading should not exceed a few hundred ohms.

What type of coils are actually installed?

Help with Arthur Harrison's 1999 Minimum Theremin Design (by dewster)

"Thanks for your response! I actually figured out the problem today - the audio jack I'm using has 3 wires soldered to it, and I just needed to connect the third one to the power line. I have zero idea how or why that works, so if you have any insight into that that would also be much appreciated" - Chloe

By "power line" I assume you mean AC ground? If so, that makes sense - Theremins require a good ground in order to function properly.

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

I hope I've been of some help!

Of course, as always!

Most of these types of issues are definitively resolved via functional prototype. Doesn't have to be fancy, cardboard from the recycling bin usually works great.

In fact, my first build was intended to be a prototype!

Help with Arthur Harrison's 1999 Minimum Theremin Design (by cchen427)

Hi Chloe,It looks like you're running your antenna wire right under your audio cable? I would keep them separate, that wire is just as sensitive as the antenna. I couldn't quite see, but it seems you have a scope on your bench? If so, I'd start by probing all of the oscillators to see if they are functioning.If it suddenly stopped working, there is a chance that ESD damaged the IC.

Thanks for your response! I actually figured out the problem today - the audio jack I'm using has 3 wires soldered to it, and I just needed to connect the third one to the power line. I have zero idea how or why that works, so if you have any insight into that that would also be much appreciated

Help with Arthur Harrison's 1999 Minimum Theremin Design (by dewster)

Hi Chloe,

It looks like you're running your antenna wire right under your audio cable? I would keep them separate, that wire is just as sensitive as the antenna. I couldn't quite see, but it seems you have a scope on your bench? If so, I'd start by probing all of the oscillators to see if they are functioning.

If it suddenly stopped working, there is a chance that ESD damaged the IC.

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

Thank you for your precious help! - André

I hope I've been of some help! Most of these types of issues are definitively resolved via functional prototype. Doesn't have to be fancy, cardboard from the recycling bin usually works great.