I haven't dealt with UREI since I worked in pro sound in the 80's. I have a few manuals. The DJ mixer was an updated versioin of the classic Bozak. Like all UREI it used all metal film resistors, TLO and NE55xx opamps, film caps etc. Level controls were sealed. Easy to work on. I repaired a couple amps and they were fun to work on. I still have the rumble filter, a necessity then for dealing with warped records and big subs.