I have a H&K Tubemeister 36 which has an output impedance of 8-16ohm. This is from a single output socket without any need for output switching or Tx taps. It has a very over-engineered output stage, 4 x EL84s and an oversized output Tx to prodce 36W, to handle the mismatches involved. I have 2 x 112 cabs with a 8ohm Celestion Vintage 30 in each. I want to wire in the ability to drive either, one of them at 8ohm or the pair at 16ohm, hence series connection through a slave socket on the main cab. Does anyone have any experience with this setup? I'm sure it can be done reasonably with switching on the slave jack socket, but I am leaning towards adding a slider switch to the jack plate to handle the changeover. Yes, I am aware that a blowout in either speaker would unload the output stage which would be a "bad thing" for it. It won't like driving an open circuit but I'm pretty sure the H&K will handle it for a short period and, let's be honest, if your output suddenly cuts out you generally stop playing! No playing, no output valve/Tx signal current, no change to quiescent current, no problem. As an aside, has anyone ever come across a protection unit which senses the presence of both voltage and current at the speaker output of the amp and pulls in a load resistor when it sees voltage but no speaker current?