"** It does if you mix up devices. "

Not much. In each bank you got the bases all connnected directly together
and the emitters are only separated by 0.33 resistors.

** If you have 3 of one kind on one side, then 10 ohms drops to 7 and the
pre bias is skewed.


"** The relay contacts will arc and burn soon as they open under a DC
fault. "

Well now I got a solution to that believe it or not and I am surprised that
noone does it. (or maybe they do)
take a nice 47 uF or so bipolar cap across the contacts. Period. think
aabout it no before to go saying anything.

** Far cheaper to use a triac, DC crowbar to protect speakers.

OR a changeover relay wired to open the output link PLUS short the speakers
to ground under DC fault conditions.

Must have installed 50 of those in PL400s and PL700s years ago.



.... Phil