Sunn Concert Controller from back in the day. Bought this for $75 some years back. The reverb didn’t work and two of the six channels didn’t work. These are old pics.
An awesome feature of this amp is that is has a tone knob for the reverb — you can control if it’s shimmery and bright or underwater, submersive sounding. Also has a reverb master volume, with individual reverb volumes per channel.
Once you take this out of the chassis and remove screws holding the two chassis panels together it folds open kind of like an oyster.
Preamp is on the left with three identical PCBs with volume and tone circuitry for two channels each. PCB at top left is for reverb tone and volume, and master volume..
In the back is the EQ and the ins and outs for each channel. Right side is the power supply and output section.
This was worked on in my DIY novice days. It had a broken solder connection inside the reverb tank and an intermittent at a jumper wire going from one of the preamp PCBs to the power amp section, making the two channels cut in and out.
Preamp shot. Compared to Sunn Concert Lead and Concert Bass this amp has more clean volume. Makes sense since it is a PA. It also has a master volume which can be useful, unlike Concert Lead and Bass.
Power amp is identical to Sunn Concert Lead and Concert Bass amps. Reference the silver face era of their schematics.
This is the reason all the knobs and EQ sliders aren’t broken off. Thank you Sunn.