A professional quality
sound card created by
Emu. The APS used to be
the shit. It's still a pretty good card, but it's kind of
dated.
The great thing about the APS is/was that it provided the same kind of sound quality as the Proteus 2000 sound module but cost a lot less (presumably because all the UI was handled through the computer you'd plugged the card into, and not through a bunch of knobs, dials, or switches on the front panel), and that on top of that you could create new samples with it, whereas to do that for a Proteus you'd need another rackmount sampler from Emu.
The APS uses the SoundFont format, which Emu created for Creative.
The bad thing about the APS isthat it can only handle 32 megs of samples at a time. This seems like a lot when you start playing with the card, but the simple fact is that if you want high-quality samples, you need a lot of RAM. Emu intended to release a new set of drivers for the card that would expand this to however many megs of RAM you wanted to use, which had a lot of people very excited. However, as of this date, those drivers are 'permanently on hold'. A lot of people took Emu to be saying that they were definitely releasing the drivers, and are now quite pissed off at the company for not doing so. The truly painful thing is that the drivers apparently exist in an alpha state, and have been demoed to great applause, but Emu won't allocate the time to debug and release them.
Why the hell not?, you ask? Well, near as anyone can tell it has to do with the fact that Emu was bought out by Creative. More detail can be found in my Emu writeup.