Marshall 8004 Power Amp Solid state 40W per channel mono/stereo power amp. It can be run in either mono or stereo and both outputs can drive a minimum of an 8Ω cabinet. 1u high rackmount The output is switchable from a liner to the Valvestate mode, which is supposedly more valve like according to the blurb. There are two inputs A & B, and B can be used as the mono input if you're not running in stereo. There are two matching 8Ω outputs, A & B, which can be again run in stereo or mono.