It's important to keep the B3s away from compact flourescent, or other flourescent lighting, as these produce RFI (radio freauency interferance).
Usually if you're about 5 or 6 feet away from a CFL or flourescent light, you're ok, and should not have any raspy, or scratchy sounds.
Try the instrument in another location, or even a friend's place, ect. If you still notice scratchy sounds in there with the tone, there may be a deffect at issue, and Dan Burns will need to know. He's good about responding quickly, and will certainly repair the theremin in that event.
Also, avoid playing with the theremin too close to a wall where an electrical lin might be running too close to the theremin. Other electronic devices like monitors, computers, and even cell phones (mobiles) can also cause RFI on theremins.
Some other things to try: Check connections. Check audio cables don't have loose connectors. Make certain the power connector is fully inserted as well as the audio cable. Also, check a different amp, and see if that might be suspect or not.
Also, one way to determine if RFI is entering via the antenna, you can try lowering the antenna a bit each time, and see if the audio artifact goes away. If it does, then you can start looking around the house for whatever might be causing the RFI and turn that item off, or move it away from the theremin, or the theremin away from it.
At the very least, do let Dan know at support@soundslikeburns.com regardless.
Do let me know how things work out.
