Originally posted by AndrewT
However if two sources or a source and an amp have both got audio ground connected to safety ground then isolation when deselected is not the issue. HUM, lots of it, when selected is the major issue.
There is a solution but I suspect the switch type is not readily available if at all.
The signal could be switched break before make and the ground could be switched make before break. That may give you what you need. A selector with the tracks specially made for this purpose could easily be manufactured. Similarly relays with delays could achieve the same.
I favor this approach. It's fairly easy to custom order a switch like this. Making the grounds before braking while switching may prevent pops and hum while switching. Also, if the input jacks have grounds isolated from the chassis, connect the input jack grounds to the chassis via a capacitor or capacitor resistor combination with leads as short as possible to prevent the "antenna effect".