get thee a Chase RLC-1 Remote Line Controller. They were made to add remote control to existing non-remote equipment.
105 db Signal to Noise Ratio is true: I and my friends are simply unable to hear whether it is in or out of the signal path. In, you get remote volume, balance, mute, treble, bass, and it has 4 selectable Line Level Inputs. Use it direct, to an input, or thru a tape or processor loop.
You MUST have the remote, there are no controls on the unit. Any RLC-1 remote will work, they all use the same KP-1 Remote.
Adjusting balance, from your listening position, for your specific needs, or for specific tracks, once you have it, it is amazing how much improvement to imaging a small adjustment can make.
You can have a problem with balance in your system, from who knows what: compensate, keep listening, enjoy, find and fix the issue later at your convenience.