So, been reading about for hours and not getting far. . .but:
. .these "balanced" outputs from the head unit. . . do you need to keep the Vibe switched "High" level inputs even if I have coded the HU to Hi-Fi to put out low level . .
I am thinking that perhaps when switched to "Low" level input, as I have done, the Vibe is expecting the signal on the RCA pin to be the signal and the shield to simply be 0V. . .which is not the case with the Hi-Fi configuration because of these "balanced" outputs.
I have read a thread which says the Vibe amp supports balanced outputs but perhaps only when switched in "High" level input mode?