Defunct brands-

Yep,

 Years ago I had a SUMO Electra preamp that lost a channel and when I tried to get it repaired, I got the cold shoulder from everyone.

Yea tavish design....no longer selling their phono preamps, but he will still service them i am hearing ....oh, cannot forget about the radio shack Realistic brand...they made some pretty darn good speakers back in the day. I had the Optimus 10's with passive radiator...they were awesome. 

Verity

Altis Audio

Merlin Musical Systems(just had my driver's upgraded by Rich Brkich)

Audio Magic 

Counterpoint 

Jerry Ozment's tube dac(can't remember the name). 

It's easier to think of what IS still around from the high end as it was defined in the 70s and 80s, rather than what brands are defunct.  Nearly all of the best are either gone or someone bought the name and now sells much lesser gear under the same imprimatur. McIntosh, which actually dates back to the 50s, is one of the rare exceptions. I guess Conrad Johnson is old enough to qualify as an exception.