Defunct brands-

Cambridge Soundworks who actually had stores in malls to sell their equipment.  Bought equipment about 30 years ago.  I had a 5.2 system and a 7.2 system with a pair of 4 way towers with 300 watt amps in each to power the woofers.  After they went out of business one of the amps went and after several attempts at repairing it I sold the towers and center channel.  I still use 4 of the surrounds and I’ve replaced the 5.2 system with a Sonos system.  

Boston Acoustics speakers which were great in the late 80s and early 90's.  Dartzeel integrated.

Sonic Frontiers SFP-1 phono pre. I recently had Parts Connexion out of Canada refurbish and spruce it up. Replacing all of the caps with Mundorfs. The filtering caps were easily 5 times the size of the original caps. I replaced the tubes with Gold Lions. And now it is quiet as hell, sounds great, and will probably last another 30 years.

Brands I’ve owned that are gone

KLH

Rectilinear speakers

Connoisseur turntable

Shure cartridges 

Cambridge Soundworks

NYAL-New York Audio Lab. My one and only experience with tubes. Tube Pre and hybrid tube MOSFET amp. Back in the 90’s. Heat and tube noise cured me.