Well, those AlphaBass amps are kinda hard to find, supposedly they weren't built very long; I've heard them being called the "poor man's Mesa Boogie 400+" - but since I've never had a chance to try one of those, I can't compare... All I can say is that it had a great, warm tube sound, but one that was cleaner, less "brutal" than an Ampeg SVT.
That shared rehearsal place was really cool because there were 4 bass stacks in there: some Trace Elliot with an EQ with a gazillion bands, with 1x15 + 4x10 cabs, an SWR (sorry forgot the model - that one was my least favorite of those 4), and some cheapo Laney - and the Peavy Alphabass (also eith 1x15 and 4x10 cabs) was by far the best-sounding of the lot.
(As an aside: another cool/weird amp, but for guitar, at that place was a SOLID STATE
Vox AC30 - which actually sounded quite good, too...)