My first tube amp back in 1975-ish was the big sister, a Bogen CHB35A that had two inputs with the old threaded mic connectors. I ran that with a pair of Switchcraft 1/4"-to-threaded adapters sticking out the back. That amp was stock, just a guitar plugged into a cranked-up PA amp. Awesome for a while, but soon replaced with a used Fender Twin, followed by a Hiwatt and many years of Marshalls.
The CHB20A was just used as a donor chassis & iron. There's nothing left of the original circuit, and the old mic connector on the back was cut out and replaced with speaker jacks. I'm still using Bogen's old strip of screw terminals as my speaker impedance selector, though.
"Daddy grips the wheel and stares alone in to the distance. He knows that something somewhere has to break." - Sting