Theremin pitch knob question

Posted: 7/15/2014 9:59:12 PM

Joined: 7/15/2014


Just 3 weeks ago, I purchased an Etherwave Plus theremin, and I'm tuning it so that I can cover an octave with my hand (for example, being able to get a C4 with my hand closed in a position and then a C5 while completely opening my hand in that same position). However, I'm noticing that each day I have to turn  the pitch knob clockwise a bit more in order to get the same tuning. When I first got the theremin I achieved this tuning with the knob in its middle position, and today I'm having to turn the knob fully clockwise in order to play. It's like each day the notes are further apart (and I get a smaller range) so I need to compensate this by turning the knob clockwise a bit more, but the problem is that if this process continues I'll not be able to compensate for this any longer (since the knob is now almost turned fully clockwise).

Please let me know if what's happening to me is normal, if you know why is it happening and if there's anything anything I can do to fix it.


Thank you very much!!

Posted: 7/16/2014 3:25:52 PM

From: Scotland

Joined: 9/27/2012

Hello Ikary

In light of more experienced people (Thierry) to answer this question, I'll have an attempt at answering it.
My guess would be that it is the ambient temperature of the surroundings which are causing the electonics inside to change which means that you have to re-adjust the pitch correction and in doing so, the position of the pitch knob is advancing clockwise from day to day.
It is possible that an internal adjustment might be required if you find that the knob is rotated as far clockwise and needs to go further.

In December (cold and Winter) my Etherwave pitch was adjusted to around the 12 noon position and as the Summer has progerssed, I have had to adjust it so that now, it is around the 3pm position.

Thierry though will shed light on this matter I'm sure.


Posted: 7/16/2014 3:31:41 PM

From: Tucson, AZ USA

Joined: 2/26/2011

Ikary the world of theremin has been thinning in recent years. I understand what you are asking but not technical enough to give you a proper answer. Every theremin owner should become familiar with the proper method of tuning the instrument internally. Thierry should be along when he gets time, definitely the brightest mind for explaining things short and simple.

Most theremins pitch drift at warm up and should reasonably stabilize after that. Are you near Arizona?

Roy beat me to the punch, we should all send Thierry gifts as he gives so much of his time. That's him trying to get some sleep in the photo on the home page.


Posted: 7/17/2014 6:14:07 AM

From: Colmar, France

Joined: 12/31/2007

Ok, it's 07:40 AM here in Europe, I just woke up and feel fresh enough to reply:

There are many factors which influence the pitch tuning of a theremin. In case of the Etherwave Standard and Plus models, there are mainly 5 things to consider:

a) Temperature I: these instruments need a warm-up time from 5 to 20 minutes until they really "settle" and no further pitch corrections are needed. During the warm-up phase, the pitch tuning may vary from -4 hours to +4 hours if you see the pitch knob as a clock with its center position at 12 o'clock. What I do to get rid of this, is letting it powered on the whole time. Seen the low power consumption it has no impact on my electricity invoice, but it is always ready to be played.

b) Temperature II: the Etherwaves are sensitive to the ambient temperature. Increasing it by only 3°C or 5.4°F makes that you need to turn the pitch knob about 1 hour clockwise.

c) Capacitive environment: the more electrically conductive material you have around it, the more the pitch knob has to be turned clockwise. Normally, you should create a metal free space with a radius of 2m or 6ft around your instrument to avoid too nasty effects. When you tune your instrument in such a free environment and then introduce a music stand at about 1m or 3ft from the theremin, you'll also need to advance the pitch knob by 1 - 2 hours to compensate that. In all cases avoid to put electronic devices like visual tuners, smart phone etc. on top of the theremin since that will completely kill the pitch field geometry. If you'd like to use such devices during playing, buy a clip which allows you to fix these devices on the mic stand below the theremin where it is much less sensitive. In case of a visual tuner, a short glance downwards will indicate you if you are in key without affecting the pitch field and without the need to bend over the instrument (see next point).

d) The player's position: once well tuned with the player standing at arm length from the pitch antenna (as written in the manual), coming closer or bending towards it by only 10cm or 4inch will also require to turn the pitch knob by about 1h clockwise to compensate the additional body capacitance inside the pitch field. Remember that the pitch field has always a radius of > 1.5m or 4.5ft independent of your individual setting of the zero point.

e) Grounding: Each theremin must be well grounded for stable operation. This is normally done through the connected amplifier's third pin of its wall plug. The Etherwave's power supply has no own grounding to avoid a double ground connection which would lead to hum and additional noise. But an ungrounded theremin (i.e. connected to a battery driven or otherwise ungrounded amplifier) will have a floating ground potential which will make it much more sensitive to environmental capacitance. That means that you'll never find a stable pitch setting.

Posted: 7/18/2014 2:26:41 AM

Joined: 7/15/2014

Thank you very much for your answers! At moog they told me that I'll have to tune the theremin internally in order to fix this, and they gave me a few instructions. So I'll try to do that and not mess everything up! :)

Thank you very much again for your time, it was all helpful and it's appreciated!

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