Vox amPlug / Headphones problem :(

Posted: 4/5/2014 10:32:05 AM

Joined: 4/5/2014

Hi there! I'm new to this forum, my name is Viola and I'm from Italy.

This may be a really dumb question, but... I really can't figure it out by myself  -___-'

I have a problem with my standard Moog Etherwave theremin (perfectly working with a standard amp or mixer)... Last week I bought a Vox amPlug mini amp (one of these little guys: http://www.voxamps.com/amplug/ ) in order to use my AKG K240 II headphones with the theremin.

Vox amPlug mini


Well, the sound comes out from both left and right and it's pretty loud, but it's like something interferes with the antennas. The sound is more... saw-ish, and the pitch is unmanageable. I tried with different headphones, but the problem persisted.

It turned out that if I touch with my left hand the metallic parts of the headphones' connectors the sound gets quite normal, but of course I can't control the volume since my left hand is busy :/ I also tried to connect the headphones directly to the theremin (without the amPlug) and of course the sound was only on the left and really low, but it still made the same thing: it has that saw-ish sound and the crazy pitch until I touched the connector. So I guess the problem is not the Vox amPlug, but the headphones.

Are there any ways to fix this problem? Are there any headphones which can work with the theremin + Vox amPlug?

Thank you all for the attention,



Posted: 4/5/2014 10:46:11 AM

From: Colmar, France

Joined: 12/31/2007

There are no dumb questions, only dumb answers...

The problem of your setup is that as soon as you play with that small headphone amp, the theremin is not longer grounded. Grounding of the theremin is normally done through the audio connection to a "real" amplifier which is connected to a grounded wall plug. The Etherwave's power supply does not have grounding (it's a two prong Euro plug) to prevent hum problems due to so called ground loops caused by double grounding.

To solve this kind of problem I have developed a small grounding adapter which is plugged between the Etherwave's power supply and the Etherwave. From that you have an additional grounding wire with a clamp which can be connected to something grounded, i.e. a heater, some water tubing, or (but only if you know exactly what you do!) to the ground contact of a wall plug.

If interested you may contact me by email service(at)theremin(dot)tf

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