You know, I have been reading about this speedbox and have been trying to figure out how a speed controller can help the sound?
PRAT is actually something that NAIM is known for. I have often heard their brand and this term together. Seems kind of hard to understand however!
A speed controller will regulate the speed better. I guess I sound like a master of the obvious there.
Everything improves - the sound gets cleaned up, bass gets tighter, faster and deeper (at first sounds rolled off, but it's just getting rid of the bloat), imaging and soundstaging improve, etc.
Just about every tweak improves one or two things at the expense of something else. Not the Speed Box. I was a bit sceptical too, but a trusted friend talked me into it. I bought it from Music Direct - 30 day return policy - and still have it 5 years later. My Xpression sounds slow and boring without it, relatively speaking. After owning it, I think its a necessity, not a nice-ity.
As for PRaT, its very hard to describe and very easy to hear if the room is right and the system has it. Naim, Linn, and Rega are the first ones most people think of in this discussion. Bryston's got at least just as much of it IMO.
Most systems without it do a good job of putting me to sleep - Marantz is the worst offender to my ears. None of their gear has it, from the cheapest to the very expensive reference series. Think very slow, overly smoothed over sound.
Just my opinion.
