Thanks for the input folks! I'm very interested in power converters, but certainly no expert in them.
It could be a single-switch forward converter.
That's interesting, never heard of such a thing. I presume that means roughly the same kind of circuit but the majority of the energy is transfered during the "on" period... will have to look it up.
Do you have a schematic or are you guessing from looking at the board.
Well... a bit of both. The amps are both made by Lab.Gruppen (Sweden, I think) and are a PLM10000 and a LA48a. Now, Lab don't release schematics for these (and I don't think I'd be allowed to share them if they did), but I have found a service manual for the FP3400 floating round the web - this is part of the same product series as the LA48a (which was re-badged for another manufacturer).
I've attached the relevant pages from that - you'll see that it's "described" as a flyback converter, but that could be mis-translation... or mis-information?
Looking at the boards (without doing an exhaustive trace) they look very much like what's pictured.
As to the power ratings , I'm always a little skeptical about these - in general it tends to be thermal capacity that limits the output of this kind of equipment to a <100% duty cycle over timescales in the minutes. Nevertheless, they're certainly capable of pulling quite a current.
Spec, thanks for the link. Can't prommise I'll read all 153 pages tonight, but I'll certainly have a look!
In general, people are coming back with reactions similar to my own - namely "that seems unlikely". As I say though, it's a topic I'm tying to learn about so I'm keen to discuss it.
If I can get some photos of the transfomers I'll post them for your perusal.