Moog Etherwave sounds crappy - and it's not (just) because I'm a lousy player

Posted: 7/7/2009 6:28:17 PM

From: Stockholm, Sweden

Joined: 7/7/2009

Hi everyone,

I'm new to this, so please bear with me if this is a really stupid question.

I just bought a Moog Etherwave and started practising. Crappy playing aside, there is an issue that concerns me and I hope that someone on this forum can help me out.

My problem is a really nasty overtone, or really UNDERtone because it's about 4-5 semitones below the tone that I'm trying to play. It sounds a bit like a ring modulator, i.e. shitty.

The strange thing, which I discovered just now, is that when I put my left hand on the audio output while still playing with my right hand, not only does the buzz disappear but it also becomes significantly easier to find the right pitch. It's as if the intervals between tones increase. When I let go of the audio output, the buzz comes back again and once more it's nearly impossible to find the right pitch.

So far I've only been playing through a small and quite shitty guitar amp, and since I only have time to play late at night I connect a pair of headphones to the amplifier. I know it's not the ideal setup, but both the theremin and the amp are grounded so that can't be the cause of the problem.

As I said, I'm totally new to this. If anyone has an idea about what might be my problem, I'd be most grateful.

All the best,

Posted: 7/7/2009 8:22:57 PM

From: Los Angeles

Joined: 3/8/2005

Hi -

I suspect a ground problem as it goes away when you touch the audio out. I have setup recording studios before, and ground problems can be tricky sometimes to isolate. Often multiple grounds on a system can cause as much hum as ungrounded systesm. A common trick done in studios is to "lift" the ground of everything except the soundboard - you can try this same trick by "lifting" the ground of either your theremin or your amp (in other words, get one of those grey adapters that allows you to use grounded plugs in ungrounded outlets). Try this as it may fix your problem.

It ia also the sad truth that some house wiring systems just create noise in audio gear - if that is the case, you need a filtered regulated power strip - these are sold for studio gear and also for computers.

You might want to try these first - otherwise you may have a problem with your theremin.

Hope that helps.
Posted: 7/7/2009 8:25:41 PM

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

Welcome to TW, Rickard..
I am not sure I have the answer to this - but I am reasonably sure someone here will.

[i]"but both the theremin and the amp are grounded so that can't be the cause of the problem."[/i]

Hmmm.. saying that grounding cannot be the problem is taking things way too far.. Grounding can ALWAYS be the problem -

1.) This 'subtone' - is it always a fixed frequency? .. Ok, it may intermodulate the Theremin tone to give 'ring modulation' type effects - but is this 'modulation' always the same frequency..

2.) Is this modulation frequency 50 / 60 Hz (mains frequency)?

3.) Is there any ground path from the Theremin other than via the audio lead and amplifier?

Here is what I would guess - but I wouldnt put money on it..

There is something wrong with a ground somewhere - When you touch the audio connector, you are grounding yourself (you are, in fact,grounding yourself the Theremins 'ground' which may, or may not be connected to actual ground..)

For some reason, I think that the Theremin ground and 'real' ground may be 'floating' with reference to each other - or there is only weak capacitive coupling between them .. When you make a strong galvanic connection to the Theremin ground, your capacitive connection to the pitch antenna starts to work as it should, completing the circuit and improving linearity

Try connecting an earth wire directly from the Theremin to mains ground.. Also - it would be wise to check the integrity of your mains sockets.. you may have a fault here, and this kind of fault (broken ground connection, mis-wired socket etc) can be dangerous.

Good luck!

Posted: 7/7/2009 9:06:21 PM

From: Colmar, France

Joined: 12/31/2007

I'm almost sure that this is a grounding issue. Some months ago, I discovered during the theremin festival in Lippstadt, Germany, that there were two different kinds of power supplies for the Etherwave standard:
The "classic" model with a 3 pole grounded mains plug and cable, the transformer block and the cable which leads to the Etherwave via the DIN plug. In this model, the mains ground is connected through up to the DIN plug and grounding is not an issue.

The "cheap" model (I discovered it only because my friend Chris, called o8o8, walked on one and I had to fix it in the night because it would be needed the next day) is a rather simple transformer with an integrated NOT GROUNDED 2 pole mains plug. So naturally there is no grounding of the Etherwave via the power supply.

I learned one thing in these old French half-timbered houses: The Etherwave (and most other theremins too) need grounding via the power supply in order to function correctly since modern instrument and hifi amplifiers have often a floating ground which is more or less decoupled from mains ground. The B3 is the ideal candidate for such tests: When not grounded, I can hear the "Radio France Bleu Alsace" station through either amplifier (Moog TB-15 and Behringer K450FX).

If someone in Europe happens to have only the new (bad) power supply, he/she may contact me for a solution by email: theremin(at)tfrenkel(dot)com.
Posted: 7/8/2009 1:12:18 AM

From: Stockholm, Sweden

Joined: 7/7/2009

Thank you for your replies - though honestly I barely understand half of them... This might be a language-related issue, but I suspect it has more to do with my lack of skills in electronics.

Anyway, I'll start with what I do understand:

@Thierry: I do have the simple transformer that you mention, with only 2 plugs, and no transformer block, just a cable. So I guess that means the theremin isn't grounded? Also my amp's transformer only has 2 plugs as well.

@FredM: I don't really know what frequency my "subtone" is; however it's not fixed, it varies according to what tone I'm playing at the moment. "Try connecting an earth wire directly from the Theremin to the mains ground" - I'm sorry, but I don't understand. How do I do this? (I'm a stupid newbie...)

@Etherspiel: I think I know what you mean and will try it as soon as possible.


Posted: 7/8/2009 7:35:15 AM

From: Colmar, France

Joined: 12/31/2007

Neither the amp nor the theremin is grounded - bad situation - impossible to play! You need a different power supply for your Etherwave!
Posted: 7/8/2009 7:59:30 AM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

Just to make this a little more confusing, I once had a similar problem with my Etherwave Pro.
My house is old (by American standards) and none of my outlets are grounded.

For a couple of months my E-Pro was producing a double tone that changed with the pitch. I tried grounding it to pipes in the bathroom and even ran a ground wire up from a grounded outlet in the basement. Nothing I tried worked.

It turned out that the distortion came from the cheap, "surge protector". 6-outlet strip I was using.
Posted: 7/8/2009 9:30:26 AM

From: Stockholm, Sweden

Joined: 7/7/2009

OK, I'm taking the risk of making this even more confusing... ;-)

I have now tried my theremin with a different amplifier, and I'm happy to say that the strange buzz is gone. So I guess the crappy amp was to blame, after all. Thanks anyway for all your tips.

However, it's still a lot easier to play when I hold my hand on the audio output. What I mean is that it's easier to find the right pitch, and that the intervals between notes become longer. Strange, but not a problem, I guess?
Posted: 7/8/2009 9:33:44 AM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

Ummm....The pitch intervals can be changed using the pitch knob on the front panel. ;-)

That also confirms one thing....
Never ASSUME the theremin is the problem.
Posted: 7/8/2009 10:20:24 AM

From: Croxley Green, Hertfordshire, UK

Joined: 10/5/2005

[i]However, it's still a lot easier to play when I hold my hand on the audio output. What I mean is that it's easier to find the right pitch, and that the intervals between notes become longer. Strange, but not a problem, I guess?[/i]

Not strange.

That the pitch field changes when you touch the earthed metal casing of the audio jack is quite normal. You would get the same effect by reaching back with your foot and touching your toe against a bare radiator pipe, for example. You are part of the theremin circuit, and theremin circuits are designed to be very sensitive to change.

That notes are easier to find when the field is wider is also normal. That's why pianists prefer a full sized keyboard to a little casio toy. Also, when you are touching something with your hand it is possible that you are reducing your amount of body movement - which also affects the pitch field.

Two parts of learning to play the theremin are learning to adjust the field size so that notes are ideally spaced for your hand motions, and learning to stand very still indeed.

You must be logged in to post a reply. Please log in or register for a new account.