Exactpower Ep15a or PS-Audio p500

Zaikesman, I said pretty much what you did (about the new PS) on another thread. It has a lot of bells and whistles and features with fancy names, but only the variable power supply is really new. Still handles noise with filters and inductors -- old technology IMO. I think powere amps do benefit from the EP-15A but I do not think they benefit much from balanced power. I save that just for front end stuff.
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Not sure that filters ever become "old technology" in the sense that we will ever be without them, but regardless, if the entire waveform is being regenerated, it seems to me PS is not depending on filters to make a dirty waveform cleaner. But will the tracking power supply actually sound better, or even as good? Supposedly the technology is new and proprietary, but as far as I know power amps with tracking power supplies of different sorts have never enjoyed much of a high end reputation (Krell's bias plateau scheme excepted). The approach, when it's been used at all, has usually been for attempts at providing increased peak power capability in what are essentially lightweight, low-cost mid-fi amps (such as the NAD 2200 I once owned), not increasing efficiency per se. I assume this is more sophisticated stuff though, and PS posts some customer testimonials to the effect that the Premier outperforms the older Power Plants sonically.

I'd think power amps would benefit from balanced power just as much as front end compenents, or nearly so. The real hitch in that theory might be getting them the balanced power at an acceptably low powerline impedance, and that's where an efficient balanced regenerator could have an advantage over a balanced isolation transformer in terms of weight and size. I thought EP offered a tranny that could run power amps, but taking another look at their site I see that's not the case, same as with my Power Wedge Ultra -- the transformers used are simply not big enough, and the outlets designated for power amps bypass them. Since I've never tried a bigger BPT or Equi=Tech unit myself, I still don't know the answer to this one. Upon what do you base your feeling about this?

Zaikesman, I think with power amps, the most important issue is the AC energy transfer. Obviously a good 10AWG PC is a plus, as well as good available AC. With balanced power units, I think the essential feature is common mode noise rejection, especially important for preamps, phono, etc., but not quite such a necessity for power amps IMO anyway. Plus of course, the size of the required transformer would be pretty large as you already mentioned.

In my reading of various threads/posts, most folks always concluded their amps sounded best plugged right into the wall, but that was usually compared with they're using some kind of conditioner. The only device which seemed not to limit t5he dynamics of a power amp was the use of BIG isolation transformers, which many people like Albert Porter seem to favor.

I did an A-B plugging my Levinson 23.5 into the EP-15A vs. the wall, (both on a ded.ct.) and couldn't really tell a big difference, so went with the EP; but I wouldn't plug a power amp into anything else (other than the wall ;--)

Now I'm using a new McIntosh MC275 Mk IV (tubes! oh Boy) which doesn't draw that many watts. Maybe I'll feed it some balanced power and see what it does?
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One thing I wonder about is whether feeding my DNA-500 balanced AC would somewhat quiet its moderate physical transformer hum. Of course, using an even bigger transformer to accomplish that task might result in even more hum in the room. But as I said, the 500 does unequivocally sound better plugged into the EP than straight into the wall, more clear and lively.

Also in the case of this amp, it so happens that it's a fully-balanced device in terms of the signal path, including the speaker output, whereas the majority of amps are +/ground rather than +/-. Steve McCormack apparently feels that differential drive of the speakers is required to get the level of fine control he's after. Based just on the sound of this amp he could be quite right, but that's not a controlled test so I have no way of knowing the validity of this. But if there's something to it, then it seems plausible the same thing might apply in some fashion to an amp functioning as a power generator feeding other gear.