sound quality using moog etherwave plus and headphones?

Hi everyone!

I'm a completely newbie to the theremin (I started playing it just three days ago), so I'm probably going to bore you with some trivial matter. I have a moog etherwave plus that I use in combo with a small Kustom bass amplifier (10W, at the moment I can't remember the exact model id) and a pair of AKG k121 headphones. Here is my problem:

config1) I link the amp to the "audio" output of the theremin and the headphones to the "phone" output of the amp and the sound quality is reasonably good :)

config2) I link the headphones directly to the "phone" output oh the theremin and the sound quality is TERRIBLE! I mean, I'm perfectly able to practice anyway, but the timbre is far more similar to an annoying buzz than to a violin or a human voice :(

Fine tuning of pitch, waveform and brightness slightly improves the sound, but however it's far from being accettable or similar to what I obtain in config1...I'm a bit disappointed about it because occasionally I have to travel abroad for work and I would like to bring the theremin and the headphones with me, leaving the amp at home. In fact, this is one of the the main reasons why I chose the "plus" version...

Can I somehow improve the timbre in config2? Is it just normal and should I simply accept it? Or should I be afraid of a malfunction of my theremin?

Two reasons:

a) the headphone output amplifier stage of the EPlus is crappy by design, a cheap TL082 dual op-amp with 330Ohm series resistors as current limiters at the outputs. Thus you can never expect a good sound quality there but rather a thin beeping.

b) as soon as the theremin is not longer connected to an external amplifier, it will not longer be grounded. This leads to a different pitch field geometry and eventually distorted sound and/or ghost tones.

Summary: what you encounter is quite normal and you should use an external amplifier with a grounded power supply even when playing with headphones (battery powered devices will not resolve grounding issues).

Many thanks Thierry!