Yeah…a stereo jack doesn’t make sense to me. I’d either want to run a head into the pair, or two heads - one into each speaker.I don't know if you saw my edit. I don't want to make this complicated and I certainly don't want any reliably issues.
My switch solution works, but feels ghostly…in the event of a short, there would be bad things.
My 3 jack solution works, allows perfect isolation for running two heads(stereo), and solid confirmation for mono use.




