New to Theremin - Possible Pitch Problem?

Posted: 1/1/2010 9:30:20 AM

From: Hamburg, Germany

Joined: 12/27/2009

Hi and Happy New Year!

I got a theremin for xmas and since then I practice every day. I start to hit the right tone from time to time now which makes me very happy! :-)

But there is one phenomenon that bugs me a bit and I'd like to get an input from you who know theremins much better than I do!

My theremin as knobs for controlling the pitch and the sensitivity of the pitch-antenna. When I turn them to a level where I can play sufficient high and low frequency tones for eg. trying something like "somewhere over the rainbow", I found out that the frequency is not stable at all:
I try to hold my hand as steady as possible and do no vibrato. And the frequency sort of jitters between the frequency I want and a lower frequency. Its pretty audible. This effect stops when I turn the sensitivity of the pitch antenna to a minimum. But then I only have a very small amount of frequency variation while playing the theremin.
The effect is not so hearable and distracting when I try to use a bit vibrato.

Do you have any input for me on this? Is this really normal? I know that I cant expect too much from a theremin that costs 200 bucks, but this still bugs me a bit!

The manufacturer told me that this is normal and a cause of the noise that comes up with amplifying the pitch antenna?!?

Greetings from Germany,
Posted: 1/1/2010 12:45:22 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

Welcome to Theremin World, Tobias.

That does not sound right to me. I think it might help to know which theremin you have. Can you provide a link to the manufacturer's website?

Posted: 1/1/2010 1:32:03 PM

From: Hamburg, Germany

Joined: 12/27/2009

Sure, its from a small german manufacturer called Golem-Instruments. The website is german only though... My Theremin is the Perseus 2
Posted: 1/1/2010 4:20:30 PM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

Ah, German. OK. If you're not getting a useful response from the manufacturer, you might try here:

(Thierry is a regular contributor here on Theremin World, and is very knowledgeable about theremin electronics. I think he might be able to help.)

I was interested to visit the Golem Instruments website - I met a person who owned either an Opaline or a Jupiter theremin from them a couple of years ago. (He was a bit disappointed with it (*)) But beyond that I knew nothing about the company. Now I know that their recent models at least are based on the Glasgow Theremin. I am sorry to report that our electronics experts are not very impressed by the design. (Search ( this forum for "Glasgow" to see what I mean.) Perhaps Golem have found a way to overcome some of its shortfalls.

(*) However, it did validate my idea for a volume-only theremin. I am currently in the process of having my etherwave modified to include this functionality.
Posted: 1/2/2010 6:20:31 AM

From: Hamburg, Germany

Joined: 12/27/2009

Thanks Gordon,
well, if its the digital Glasgow design, maybe this also explains why this theremin does not sound very warm....

I made a recording of the problem and sent it to the manufacturer and now I wait what he thinks of this. If problems are still unsolved then, I'll contact Thierry, although I dont think he will be very happy to get his hands on a Glasgow based design (from what I read in the forums after a search..) ;-)
Posted: 1/2/2010 8:16:46 AM

From: Southampton, England

Joined: 1/2/2010

hi there
i am new here as i only got my theremin for xmas to, I am currently having a problem with it to,
I have the Moog etherwave standard that i got in kit form,

the problem I have is that the zero beat point seems to get closer to the antenna on its own (over the space of abut 15 minutes of turning on and tuning up ) until it stops at about 6" - 8" which makes it very hard to be play accurately,
has anyone heard of this problem before?
i hope it is something that is easily sortable as i have waited about 3 years to get a Theremin and i cant wait to start using it properly,
thanks everyone
Posted: 1/2/2010 8:32:39 AM
Brian R

From: Somerville, MA

Joined: 10/7/2005


Hello, and welcome to Theremin World!

It's normal for a theremin to require 15 min. or so to "warm up" before the control fields stabilize in size. So, try leaving the instrument on for 15 min., and [i]then[/i] adjust the Pitch knob to create the desired size of pitch field.

All best,

Posted: 1/2/2010 10:01:42 AM

From: Hamburg, Germany

Joined: 12/27/2009

Hey all! My problem is solved! And I am soooo happy!

I once again thought about it and found out that my HiFi-Amplifier which the Theremin is currently connected to, is not grounded over power supply. Guitar amps and such normally are.. The theremin is also not grounded over the power supply, so I connected the power supply ground to the audiojack of the theremin - TADAAA! Now I can play perfectly clean frequencies. I got a little bit of groundnoise now though but compared to what I had before, this is heaven! ;-)

Greetings, Tobias
..... who is now going to practise... :-)
Posted: 1/3/2010 1:59:56 AM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

[i]"Now I know that their recent models at least are based on the Glasgow Theremin. I am sorry to report that our electronics experts are not very impressed by the design." - Gordon C [/i]

"based on the Glasgow Theremin" could be hugely different to "it is a Glasgow Theremin"..

There is nothing 'wrong' with the core concept of the 'Glasgow' Theremin.. it is a concept used by Bob Moog in some Big Briar (91 series?) Theremins long before the AWFUL Glasgow implementation of the idea.

Fundamentally, the Glasgow Theremin consists of a 'front-end' capacitive sensing circuit producing control voltages (pitch and volume) which then drive voltage controlled synthesiser circuits (VCO, VCA).. The Theremin is clearly split into two parts - the controller (analogous to a keyboard or ribbon controller) and the sound generator / synthesiser.

The big difference between the above and 'standard' theremins is that, with a standard heterodyning Theremin, the audio generation is an integral part of the 'sensor' circuit.. The 'controller' and 'synthesiser' cannot be split - they are one and the same circuit.

Voltage control offers huge advantages over the heterodyning method - one can scale the CV to whatever one wants, and therebye cover as many or few octaves as one wants.. one can simply add or subtract voltages to the pitch CV which simplifies tuning.. Lots of BIG advantages, and if ithe circuitry is well designed (unlike the Glasgow circuits which are so bad that they are disgrace to the art) then there is no reason why it should not be a good Theremin.
Posted: 1/3/2010 5:03:49 AM

From: Southampton, England

Joined: 1/2/2010

Hi there brian r
thanks for the info, that makes sense about the theremin taking about 15 min's to warm up, i did try that after you said and it did stabilize but it did so at about 6" away from the pitch antenna to the zero beat point, i am assuming that i will have to tune the pots on the circuit board to bring the zero beat point back to arms length, do you think that is what i should do ?
thanks again for your help i really appreciate it,

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