Theremin help

Hi, I've had my theremin for a few months now, an etherwave standard and I had some general questions I needed answered. 

1. When I plug my headphones into my amp and directly into the theremin I only hear sound from the left ear, is this normal?

2. The pitch range gets smaller everytime I play it and I've had to open it up and tune it a couple times just to get the pitch knob to be in an acceptable range, what's causing this, and can I prevent this from happening?

Thanks!

I know the answer to number 1, but not number 2

1. It is normal! The output is a mono instead of stereo -- meaning when the theremin sound is "fed" into the amp, it isn't split into two. Therefore when you use headphones, it is still feeding one, unsplit, sound into the headphones.