Exactpower Ep15a or PS-Audio p500

I own an EP-15A and like what it does.

The rap on the older PS Audio regenerators was that they necessarily were somewhat inefficient due to their use of a traditional linear amplifier to regenerate the entire powerline. Though I don't know the details, and haven't myself heard either the old or new PS units, it would appear that they've changed over to switching amplification now instead.

This would make them more similar to the EP, but without the feedfoward comparator technique, i.e., they still regenerate the entire powerline. Since the switching-amp architecture allows this to be done efficiently, it seems there'd be less relative advantage in EP's method other than greater compatibility with power amps and TVs, while on the other hand the PS approach allows additional features like MultiWave (of which I don't personally know the benefits) and balanced output (which I do, courtesy of my API Power Wedge Ultra's balanced isolation tranformers for sources only, and wouldn't want to give up). I guess one other potential advantage of the EP technique remains that if momentary demand exceeds capacity, the unit simply switches over uninterrupted to unregulated wall power and then back again after demand subsides. However, in my time with the EP using fairly high-powered amps driving 3-way towers in a mid-sized room, this function has never been necessitated at any volume level I can comfortably play.

But I will say this for the EP: Defying some 'conventional wisdom', my present power amp (a McCormack DNA-500) sounds distinctly less impressive plugged straight into the wall than into the EP. So -- maybe an EP for the plasma and power amps, plus a PS (old or new) for the sources?

Well, scratch my speculation about the new Power Plant Premier using a switching output amp. When I ACTUALLY WENT TO THE PS AUDIO WEBSITE AND READ ABOUT IT (real tough, that!), it was made clear that what's different now is a new type of tracking power supply, but it's still a linear amp, said to be pretty much the same as before otherwise but with a claimed 85% efficiency instead of 50% (Exact Power claims 97% efficiency for the EP15A). PS maintains that class-D topology isn't compatible with a power regenerator (they do use ICE in power amps) because of ultrasonic noise.

The Power Plant Premier (they dub it P3) now also features the ability to switch over to unregulated wall power if capacity is briefly exceeded (such as when an attached power amp is turned on from cold), like the Exact Power. Strangely if you ask me, PS doesn't play up their product's ability to deliver balanced AC without having to resort to an outboard balanced isolation transformer-based device. But it does now feature five of what they call "Iso-Zones" -- what appears to be a combination of inductive and parallel filtering applied to each of the five outlet duplexes, said to provide inter-component isolation -- similar to (but presumably not quite as absolute an isolation as) what I presently get from the API Power Wedge Ultra iso-tranny unit following my EP (who also offer balanced iso-tranny units to follow the EP15A). But I'd need to add yet another transformer-based component to get balanced AC to my power amp. Seems PS have also added a remote control, turn-on sequencing, cable and tele connectivity, and reduced the Multi-Wave complement down to one choice, the most popular one. And incorporated the surge protection into a removable module that can be more easily replaced in the event of protective failure.

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?

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.