Basically, you’re going to have to face the fact that the Optigan is inherently a very buzzy, noisy machine. Unless you want to completely replace the grounding and amplification system, your only hope is to try to minimize the buzz and maybe notch it out with a multi-band EQ or some noise reduction DSP. The first thing you can do is try reversing the way the power cord is plugged into the wall socket. In fact, there’s a sticker on the back of every Optigan which tells you to do this. Find the polarity that gives you the least amount of buzz. In a reverb-equipped Optigan, you have another problem to surmount. If the foam insulation has eroded away from the chord button contact area, you’ll get a nasty buzz as your hand gets closer to the buttons. I’ve yet to find a suitable replacement insulation, but I’m sure there’s something out there that will do the trick.