Robin, thanks for the insight. I am using a switching jack on the input and it does short to ground when nothing is plugged in. The input is isolated when a plug is plugged in though. The issue I’m having appears at the output side of the amp between the OT black wire and, in my case, the yellow and white wires. From Beelzebum I understand that this is how those wires should read with a multimeter from the OT.