Hello, Thank you all. I am understanding some of the nuances better from your points.
My project does not involve a board. I bought a handmade tube preamp. It is an incredible upgrade for sonically on many levels. We have been using it without the gain disable switch on.
When I flip the gain disable switch, music only comes from one channel.
It is basically one wire to wire connection that needs to be soldered.
I might know a guy down in Greenfield, Mass who repaired my son's guitar amp a while back. I could give him a call and see.
It is just the is question of the time and cost for someone else to do it compared to buying some equipment and trying to learn something new myself.