You won't believe the problem this one had! Customer brought it by complaining of 'noise' and generally 'bad sound'. It'll be obvious why when we get a look inside.
The Sunn Coliseum Bass amps are known for being used by John Entwistle of the The Who during the early 1970s. Here's an ad from the era depicting Entwistle's endorsement: http://www.thewho.net/whotabs/images/sigs/74JAESunn-JAE.jpg
"The Coliseum head first appeared in the 1970 catalogue. It featured two channels and five simple controls: Lo Bass 20-80Hz, High Bass 80-250Hz, Mid 250Hz-1Khz, Treble 1-10KHz and a master volume. There were also tone range switches for the mid and treble controls and a Norm/Brite switch for the input. The Coliseum was fully solid state, boasted an output of 320 watts at two ohms and was built to power a pair of 1×18” bass reflex cabinets."
Source: http://www.bassguitarmagazine.com/tests/sunn-coliseum/