Not tube, all transistors, but it uses FETs in the preamp (must be one of the earliest FET amps), and the output transistors are driven by a transformer - which can saturate (a good thing tonally).
There are two versions, the earlier model has two discrete channels and to use both you need an A/B/Y box - one channel has reverb, the other has distortion/boost. The later version has a single channel with both.
I only have experience with the earlier version, and after a tuneup they're great amps. EXTREMELY loud and tonally quite similar to a 50W nonmaster Marshall.
