Attached to each amplifier is a little trimpot for adjusting the chord/keyboard volumes. On most Optigans, these trimpots can be accessed by the little holes on the back of the unit. If you still can’t get much sound out of an amp, or the sound is particularly distorted, the the amp has gone bad and would ultimately need to be replaced. If you’re clever with this sort of thing, I’m sure it’s very easy to come up with some kind of alterate amplification scheme. Keep this in mind, though, if you plan to switch the chord/keyboard amps around: The only difference between the two amps is the presence of a small jumper in the lower left hand corner of the amp. Only the keyboard amp has this jumper: the chord amp does not. It’s fairly easy to add or remove the jumper if you decide to switch the amps around.