I think we need to know how this has been constructed, wiring from OPT, conditions of test when this happens (i.e. what's on the output XLR/ jack) and amp input to understand what is going on.
The XLR out is supposed to connect to PC to be used with IRs. The problem occurs either way when the Jensen circuit is disconnected from PC or from the reactive load. I'll check with my PC scope if any oscillation is present when ground is lifted.
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