I am very impressed with this preamp--yes, it's a preamp, though you can use it as a stomp box in front of another preamp if you must. I play it into the effects return on my Fender Rumble for practice, but I can also send the signal straight to my audio interface and into my computer via the XLR Out. This would also work for a live gig as a DI box that allows your signal to go straight to the mixing board. It can be powered by 9V, AC adapter, or phantom power via the XLR, so there's some good versatility in terms of supplying juice. Two inputs--A and B--for two separate basses and three presets for each, or if you only need one input then you have six presets to cycle through.
Tone-wise, it's incredible. I can go from mellow to flip-top to over-overdriven in a heartbeat. It emulates the Ampeg SVT (hence the VT Bass name) very, very well. With some knob-twisting on my Jazz Bass, I can use this preamp dial in some great Geddy Lee-style tones--from Moving Pictures to Counterparts (a la "Leave That Thing Alone") to Clockwork Angels (a la "The Anarchist").
I don't know that I'll ever need to use anything else in my bass rig--except maybe some effects like delay and chorus (and the VT Bass Deluxe provides an effects loop just for that purpose). Buy one from Sweetwater today and be amazed!