S'not really a powersoak such as those used for valve amps (hence the inverted commas...); it's just that it can be 'tamed' to not belt out 100w or whatever all the time, yet still sound... Well, whatever it sounds like. Useful, maybe, for finding a 'sound' at home, and replicating it in rehearsal without too much faff.
In my day (yes, all those years ago...), our 'system' was to have the amp at full blast, but to lay the cab face down on carpet, and record that. With the Hiwatt amps we were using, it wasn't safe for one's bone structure to stay in the same room, otherwise.