www.hifiplus.com

EQUIPMENT REVIEW
The ExactPower EP15A Sub-cycle Regulator

by Roy Gregory

Huh? I can almost hear you scratching your heads. What on Gods green earth is a sub-cycle regulator? Well, thats a good question and when it comes to ExactPowers EP15A, its pretty much the only question. Okay, so lets back up a bit. Mains quality and its effect on hi-fi performance isnt exactly news. Nor are most of the many and various responses to the problem, ranging from battery power supplies through to the dogged insistence that any deviation from a bog standard IEC mains lead (as supplied with your shiny new unit) is not only a waste of money but actually detrimental to the sound quality. Leaving the religious crazies aside for the moment, most of us have reached the conclusion that what we use to connect our equipment to the wall socket has an audible effect. How important that effect is: how big; how manageable and ultimately how relevant; is where we generally differ. However, slowly but surely theres a school of thought emerging that says that your mains cables are not just the first link in the chain but also the most important. Once you get your head round the fact that there are good reasons to take that point of view seriously even if, ultimately, you reject it, then the vast expenditure of energy on just about anything to do with getting electricity from the socket and into the system begins to fall into some kind of perspective. Of course, the range of cures on offer goes way beyond simple cables. Isolation transformers, parallel and inline filters, various bits of black magic, all are out there and all have both their advocates and their detractors. But the Rolls-Royce of mains treatment remains, unquestionably, the regenerator. Like just about everything else to do with the mains, regeneration has received a mixed press. The first and in many ways the most impressive units Ive come across are the well-received Accuphase designs. However, these are both seriously expensive and offer a strictly limited capacity, such that a CD player and solid-state pre-amp is about all you can connect to the smaller version. Even a low-powered integrated proved too current hungry, while valve electronics are seriously problematic. Other cheaper incarnations such as those from PS Audio are not nearly as successful, while attempts to jazz-up the formula with additional features seem to have diluted the engineering rather than reinforced it. Enter then the ExactPower designs (there are two, the EP15A reviewed here, and the EP20A which offers higher capacity and more outlets). The basic principle that underpins the concept of regeneration is that you take the mains as presented by the wall-socket, clean it and break it down (generally to DC) and then use that DC to run a high-power amplifier which outputs a steady 50 (or 60) Hz. This is fine in theory, but with two major stumbling blocks: any grunge that you dont eliminate is promptly amplified and the power rating of your amplifier limits the available current at the output. And thats before you even get to the issue of internally generated grunge from the device itself. Perhaps its not surprising that regenerators that work cost an arm and a leg! ExactPower have managed to pulloff that cleverest of tricks, employing some seriously sophisticated technology to actually simplify a process. Rather than trying to smooth or filter the incoming signal, what they do is amend it! The EP15A generates its own internal, amplitude stabilized AC reference. This is then used for comparison with the incoming AC power. The clever bit is that the unit then applies real-time, feed-forward correction to that incoming waveform, trimming and shaping both it and the voltage as it goes. Naturally this requires some considerable on board capacitance as well as a blindingly quick response from the circuit itself. The capacitance is there to see, the circuit is, frankly, well beyond my ken. However, for those of a technical bent theres a ton of material available in the form of a white paper published on the companys website. ExactPower claim correction within the space of a millisecond, while the ability to deal with discrete parts of each individual cycle explains the unfamiliar terminology adopted for the name. (We could of course just call it a mains conditioner and have done with it, but that rather misses the point.) The resultant, cleaned signal is then used to drive the output power amp, resulting in plenty of

REPRODUCED FROM HI-FI+ MAGAZINE www.hifiplus.com
headroom and a significantly less intrusive overall solution one with a few interesting fringe benefits. Because it doesnt stand between the supply and the amplifier, the circuit is in no way current limiting, supplying 15 Amps from each of its output sockets, while the amplifier itself can handle a continuous output of 1300 Watts. Its output impedance is also actually lower than that of the wall socket, further aiding audio performance. Whats more, if the unit senses
possible high-frequency oscillation of the output circuitry. The unit itself is housed in fairly slim, standard width chassis, unsurprisingly, roughly the size of a compact, solid-state power amp. But dont let the svelte exterior put you off. Lift the lid and the interior is packed, which probably accounts for the substantial 14kg weight. The front panel is beautifully contoured and visually its relieved by a feature line that surrounds the single, centrally mounted, blue LED alpha-numeric display and its flush-
on the US version offer a significant potential advantage here. However, in theory, all you have to do is plug the ExactPower into the wall and the system into it and away you go. In practice there are actually a few decisions to make. Yes, you can do it the ExactPower way, but I actually preferred a slightly different approach. First issue is the question of mains leads. ExactPower actually offer the option of buying a Nordost Vishnu power cord along with the unit, which is advice worth noting. Whether you use Nordost or an alternative brand of mains leads, youll want to use them both into and out of the EP15A.
over-current or over-voltage conditions at its output (often caused by power amp switch on or really thrashing a big rig) then rather than shutting down the system, it simply shuts itself down. The system simply reverts to unregulated power, direct from the wall feed until the EP15A is able to re-impose the corrected signal, normally after four seconds or so. I dont know exactly how long because even my most enthusiastic efforts failed to cause a flutter. Over voltage at the input is another matter, and spikes of over 245V or dips below 200V cut power to the outputs in order to protect the system. Also, because it doesnt employ brickwall filters to block high-frequency irregularities, but simply corrects them, it remains a truly wide-bandwidth device. However, both EMI and RFI filtering is included, thus preventing

mounted control button. Below it youll find the main on/off switch. The EP15A is available in either a black or silver finish to suit different set ups; and while were on the subject of finish, it, the fit and graphics are all first rate. This is a product that can be sat happily next to even the most esoteric equipment without spoiling the view. The rear panel offers an IEC input and five (eight in the US) 13 Amp sockets. These are divided up, three for analogue units and two for digital, the latter employing additional filtering to prevent digital nasties getting back into the unit. Thats about your lot. The EP15A has sufficient capacity (if not outputs) to run even large and complex systems. The extra outputs
This unit is not an alternative to decent leads, rather it complements and underpins their performance. Likewise, I preferred the sound of the system running from the Thor distribution unit, itself plugged into the ExactPower, rather than connecting the system direct. Now, there are a number of possible reasons for this, not least the fact that the Thor itself is not a passive unit. However, the most prosaic is that employing the Thor not only star-earths the system but allows connection to my clean-earth spike sunk in the garden. The lack of an earth post on the ExactPower is, in my opinion,
a regrettable oversight, albeit one that should be easily correctable. With the system connected as described, operation is simplicity itself. Turn the EP15A on first, then turn everything else on. The display will tell you the output voltage. Toggle the switch and it tells you the output current. Toggle again and you get the total power load being drawn (useful to ensure that youre not over taxing the unit). A final push disables the display, leaving just a single blue power indicator to show the units status. Right, lets cut to the chase: Theres no way Id have spent the time and trouble describing this device if it didnt work. Whats more, given the cost, Id not have bothered unless it worked really, really well. It does. In fact, whilst I dont have an Accuphase unit available for comparison Id say that the ExactPower is just as convincing, somewhat cheaper, and to all practical purposes, far less limited in application. All good stuff youd have to agree. As to the specifics, connecting the system in the way described, using an analogue output from the EP15A to drive the input of the Thor distribution block, the differences are far from subtle. Breaking them down, lets start with the soundstage. Youd expect added stability and a quieter, blacker background and those you get. But the upshot of those improvements is a deeper and far more coherent soundstage, with far more solid and dimensional images. Playing the Andante from Haydns String Quartet Op 64 No 6 (Opus 3 8403) the overall acoustic is far more apparent, as is the location of the instruments within, both contributing to a significantly greater sense of spatial coherence. But that

coherence extends to the music as well. The instruments are richer and more present, their contribution to the whole delivered with greater poise and purpose. Likewise, Wes Montgomerys Full House (OJC20 106-2) has greater body and presence. Take the opening title track: its easy to lose the contributions of both the piano and the double bass. With the ExactPower feeding the system, the various instruments are physically fleshed out and better separated in depth. The piano speaks with a quiet authority from behind the sax while the bass takes on a far greater
Wes Montgomery disc. Ive Grown Accustomed To Her Face is a poignant ballad played with minimal accompaniment. Montgomerys notes are delivered with a delicacy and poise that is quite captivating, the shaping of his phrases a thing of beauty. But what really comes to life is the brush work of Jimmy Cobb and the beautifully restrained interjections from Paul Chambers bass. Not only are the instruments clearly placed and separated,
sense of definition and independence, contributing rather than simply stumbling along. Whats happening here is that the notes from each instrument are developing their full harmonic character. It gives them a rounded richness and weight that rings true, yet at the same time the massive improvement in micro-dynamic resolution that enables these changes ensures that the shape and placement of notes is far more explicit and precise. In other words the sound is both sweeter and clearer, rather than trading one attribute against the other, as so often happens. Or to put it another way, the presentation is more natural, both in terms of tonality and presence. Just listen to track two on the
but the bass in particular takes on its proper size and shape, the full complexity of the plucked notes. The system even does a better job of separating off and rendering irrelevant the low-level tape noise thats present. But the best Ive kept for last. Suddenly the intimacy and directness of contact between Montgomery and Chambers is as plain as the nose on your face. The depth of their relationship, their shared musical appreciation is writ large, the contribution to the impact of the haunting, almost melancholy track huge. When the last note dies away and the audience explodes into applause for this, the least flashy of the tracks on offer, you really understand why. An enhanced listening experience? I should co-co In many ways the acid test for the ExactPower is removing it from the system. Playing Midnight Shift with the EP15A operating, I marvelled

at the solid presence and natural warmth in Greg Sarfatys voice, the clearly resolved tonality of each acoustic guitar string. The harmonica was utterly convincing,
only used it in two different environments my old listening room and the new one. Different equipment in a different place might produce different results. I can only report what Ive heard and to date the results have been remarkably consistent.
Meanwhile, and with those caveats understood, Id heartily recommend experimenting with the ExactPower EP15A. I rather suspect that, if you put it into your system and get accustomed to it, then like me youll be loath to do without it once you hear what happens when you remove it. In fact, theres one other thing that ExactPower should fit and thats a by-pass switch. That way you could reassure yourself that you are not imagining the magnitude of the difference that this outwardly simple box makes. It looks like regeneration is finally coming of age and getting cheaper too! I like it when that happens
the drumming crisp and insistent. Remove the ExactPower from the supply chain and the soundstage collapses, the images shrink and congest, the sound goes edgy, thin and tinny. Its quick and theres plenty of pace on proceedings, but the subtltys gone and with it the naturalness and most of the expression. Whilst there are those that will find the regulated supply smoother and less exciting, I say listen a little longer, cos in reality theres plenty been added and nothing taken away. In fact, dynamics are quicker and wider, theyre simply more natural. Any piece of hi-fi that seeks to interpose itself between your system and its environment is subject to several important caveats and the ExactPower EP15A is no exception. Ive not tried it with enough equipment, and perhaps more importantly, enough types of equipment to investigate its universal application. In particular, Ive mainly used it with smaller Class A and Class AB amps like the Rogue Audio Atlas and Tom Evans Linear A and B. A really powerful Class AB design might well find it out. Likewise Ive
US purchasers receive units fitted with four digital and four analogue output sockets (high-quality Hubble designs). Against this the five large 13 Amp sockets on the UK version seems a bit mean, even if the limitation is imposed by the case dimensions. Of course, used the way I prefer it isnt an issue, but those wanting to connect an entire system directly to the EP15A might actually investigate purchasing one with NEMA type socketry and mains leads to match. Hard to do mind you, if you already own a mains loom. Id also like to see that earth post fitted. One thing I havent tried is connecting non-critical components direct to the ExactPower rather than to the Thor mainly because I dont have any. But imagine a high-end, two-channel set-up with a DVD player and surround sound decoder attached for watching the odd movie. Attaching those two units to the EP15As digital output sockets rather than the main distribution unit could be a very good thing indeed.

T ECH NIC AL SP E CI FI CAT IONS
Type: Phase-locked, feedforward AC power correction and protection device. Outlets UK: US: Output Voltage: 5x 13 Amp sockets 8x Hubble Nema sockets 230V 2%
Input Voltage Range: 200 245V (UK) Peak Output Current: 25 Amps peak-peak Dimensions (WxHxD): 17 x 3.5 x 14.7 Weight: Finishes: Price: Manufacturer: www.exactpoweraudio.com sales@exactpower.com 14kg Black or Silver 2250

86equitech

8/9/04

10:10 AM

Page 46

Equipment Review

ExactPower EP15A & SP15A AC Line System

Part II

L A C K B U R N
ExactPower EP15A And SP15A AC Line System
A Second ExactPower Addition
In Part I (Issue 78, November 2003), the $1,995 ExactPower EP15A AC Line Voltage Regulator turned in a surprisingly adept performance given its modest size. It proved capable of providing power for 650 watts of amplificationreal amplifier watts, not receiver watts, which are considerably inflatedplus all the power for rest of the system including the direct-view HD moni-
Happily, the performance is commensurate with the price, making this one of the very best power conditioning solutions available
tor. The only elements of the system not powered by that single EP15A were the five subwoofers (1500 watts) and the two amplifiers located in the rear of the room powering the left, right, and center surround loudspeakers. The EP15A actively eliminates distorted portions of the AC power. The portions of the AC power that are removed get replaced by a high-efficiency digital amplifier (see Part I or www.exactpower.com for a more detailed description). This allows the EP15A to provide prodigious amounts of power without its internal amplifier having to provide 100 percent of that power. This contributes to the relatively moderate price of the EP15A and its modest physical size. There are other products available that completely recreate the AC power using an analog amplifier. These products are much more expensive, generate far more heat, and have less current capability than the ExactPower EP15A. At the end of Part I, I wondered how the system would perform with a second EP15A powering the rear amplifiers and subwoofers and another ExactPower product, the $895 SP15A that provides 15 amps of

Specifications:

ExactPower EP15A
Input Voltage Range: 85 to 140 VAC, 60 Hz Output Voltage: 120 VAC 1%, 60 Hz, 1 amp to 15 amps Peak Output Current: 46 peak-to-peak amps Warranty: 3 years EP15A Retail Price: $1,995 Weight (In Pounds): 45 Warranty: 3 years SP15A Retail Price: $895 Manufactured In The USA By: Atlantis Power Quality Systems, Inc. 9411 Winnetka Avenue Chatsworth, California 91311 Tel: 2822 / Fax: 0504 Tel Outside USA: 5364 E-Mail: info@exactpower.com www.exactpower.com

ExactPower SP15A

Input Voltage Range: 120 VAC nominal, 60 Hz Output Voltage: 120 VAC 2%, 60 Hz, 1 amp to 15 amps Dimensions (WHD In Inches): 17 x 3.5 x 13.2
balanced power. ExactPower sent a second EP15A and an SP15A for Part II, so lets see what the additions did for the system.
Adding An EP15A For The Back Of The Room
Passive power conditioners added to the rear channels have minimal audible impact. Theres a subtle improvement in the sound, but you really have to listen for it. Many movie soundtracks arent good enough to reveal the sonic differences. You have to rely on the very best movies, DVD-A and/or multichannel SA-CD to hear the small improvements in detail, spaciousness, and

lower noise floor. Active power conditioning equipment produces a much more obvious level of improvement in rear channel (side and rear-center) soundas Ive been convinced by equipment from ExactPower and Equi=Tech. The EP15A powering the rear channels really kicks up the sound quality. The DVDA of Toy Matinees self-titled album was the first thing I picked to evaluate the addition of a second EP15A for the rear channels. The space the detail the delicate nuance the EP15A was clearly making the sound from the back half of the room special once again. Toy Matinee includes almost every surround image that can be

Page 1/3

Widescreen Review Issue 86 July 2004

Page 47

incorporated in todays sound recordingmid-room images, flyovers, images to the sides, and ambient sounds. The second EP15A improved the execution of all of them. Moving on to X2: X-Men United and Finding Nemo, the improvements held up quite audibly, reinforcing that it really is possible to get more from any given back of the room system with the right sort of power conditioning. The improvements were audible on every 5.1 movie, even those originating from standard-definition cable TV on one of the movie channels. Even analog matrix surround from LaserDiscs like Blade Runner and Braveheart were clearly improved with the EP15A in the system. Putting the second EP15A on the rear channels resulted in more detail, more distinct individual sounds, better sorting out of complex mixes, cleaner and tighter sounding bass (assuming full range loudspeakers in the rear), and better integration with the sound from the front of the room, providing you are using similar power conditioning up front. Localization of sounds is improved to the point where there is pin-point imaging across the rear of the room, along the sidewalls, and at mid-roomassuming you are using point-source loudspeakers rather than loudspeakers more suitable for older matrix surround applications. Big music soundfields from DVD-A or multichannel SA-CD take on a new feeling of being a completely integrated whole without connection to any of the loudspeakersthe sound exists in the room as if there are no individual loudspeakers. The Lord Of The Rings: The Two Towers Extended Edition DVD provides nearly four hours of fascinating sound. The active rear channels really close the loop with the front channels on the flyovers, weapons fire, wizard spells, and all manner of environmental sounds from wind to battlefield noises. The rumble and integration of the talking trees was

Page 2/3

obviously improved over the sound of the (full range) rear loudspeakers driven without the EP15A. It was actually easier to understand what the trees were saying with the additional EP15A in the systemnot something I would have expected from a rear-channel-only improvement. The EP15A is an easy recommendation for all the channels in your surround system. Smaller systems with less powerful amplifiers may even be able to run the entire system from a single EP15A.

Adding The SP15A For Balanced Power
The final piece of the puzzle fell into place after installing the SP15A. This 45pound device is the same size as the EP15A (17 x 13.2 x 3.5 inches), but 12 pounds heavier. The SP15A has 10 electrical outlets on the back. Four of the AC outlets have special high frequency filtering for digital components like surround processors, D/A converters, and DVD players. This filtering keeps high-frequency noise generated by digital components from getting to other, non-digital components in the system. Two outlets are on a ground-fault type outlet with test and reset buttons. To make sure the ground fault outlet sounds as good as the other outlets, I listened to a Belles 21A two-channel tube preamp connected to one of the analog outlets and to the ground fault outletno problem, the ground fault outlet sounded just as good as the analog outlets. The SP15A is available with additional filtering for the incoming power line if you intend to use it without an EP15A. Just in case you are coming into the world of power conditioning and balanced power late, there are three sorts of technology in general use for home theatre equipment. Passive power conditioners use filters employing capacitors and/or inductors. They will remove high frequency noise from the power line but not low frequency noise or distortion. Nor will passive devices main-
tain a steady 120 VAC to your equipment. Active power line correction devices include voltage stabilizers, power regenerators, and power correction and regulation devices like the EP16A. These devices will have a mixture of capabilities so its important to know what the product you are considering will do, lest you find you could have gotten more functionality for your money. Balanced power conditioners deliver two 60VAC lines and a ground to components connected to them. Wall outlets and most power conditioning products, including the EP15A, provide 120VAC, Neutral (close to 0 volts) and ground to the connected components. The two 60 VAC lines provided by balanced power conditioners are shifted in phase so that they add to 120VAC. The two 60VAC lines allow a significant reduction in common-mode noise that would be present on the 120 VAC and Neutral lines of conventional power conditioning equipment. Essentially, the identical noise in both 60 VAC lines cancel each other out by adding to zero volts the same way the two 60 VAC lines add to 120 VAC. The result is cleaner power for your components. The simple front panel contains power and standby switches, each with a single blue LED indicating they are on. Inside, the SP15A is almost all transformera specially constructed toroidal transformer that has features to make it effective in a lownoise balanced-power application. An electrostatic shield between primary and secondary windings shunts high-frequency power line noise to ground. Bifilar winding is used to wrap the wires around the transformer core to reduce electrical noise. The more components you can power with direct power, the more your system will benefit from balanced power. The SP15As ability to deliver up to 15 amps of balanced power makes it considerably more powerful than any under-$1,000 balanced power product I know of. In fact, some similarly capable balanced power conditioners sell for as much as $2,000. Atlantis Power is very clear in their instructions to connect the SP15A to the EP15A and not the other way around. This means that the SP15A receives clean power from the EP15A. This connection allows you to connect high current devices, like separate amplifiers, directly to the EP15A in the event their current draw is too much for the SP15A. Heat is not a big concern for the SP15A. It needs some ventilation, but it is not a big producer of heat. The

www.WidescreenReview.com Issue 86 July 2004

10:11 AM

Page 48
two EP15As do produce a fair amount of heat, so plan accordingly. Video performance was clearly improved when the Sony XBR HD direct-view monitor was connected to the SP15A. There was a distinct reduction in grainy noise from every sourceHD cable, DVD, standard cable, standard broadcast, and HD broadcast. This is after the monitor was connected to the EP15A, by the way. The EP15A alone made some noticeable image quality improvements in color purity and noise. Graininess from noise was reduced at all illumination levels from blacks to highlights. Adding the SP15A pushed the envelope and made the video image quality about as good as I could reasonably expect it to get with perfect AC power. Interestingly, to get the most out of the EP15A and SP15A you need to re-use your favorite Test and Setup DVD to re-set the black point, white point, color and tint/hue controls. Fail to do that, and youll miss some of the improvements.
Comparing The Complete Package
If you were to total the cost of the two EP15As and the SP15A, youd be knocking on the door of $4,900. Thats right up there with some of the most expensive power conditioning products you can buy. The question for potential owners is whether this sort of investment is justified by the performance. The $600 more expensive Equi=Tech 5Q has a very slight advantage in dynamics and noise floor over the ExactPower trio because all the amplifiers in the system can be connected to the 5Q. But the ExactPower products have a slight advantage over the 5Q in subtle detail, spatial recreation, and pinpoint imaging. For many people, the 220VAC requirement and 185 pounds of the 5Q is just too much hassle. The combined 115 pounds of the three ExactPower products spread over three chassis makes them very easy to deal with
for install-it-yourselfers. The 5Q gives you passively filtered balanced power with nearly unlimited current capability, so a couple of thousand watts of amplifiers can be powered by it. The ExactPower trio gives you sufficient balanced power for the entire front-end and video display, though it may be a bit short on balanced power current for amplifiers. The ExactPower trio actively regulates the power line to 120 VAC and actively removes not only noise, but distortion on the power line as welltricks the 5Q cannot do. The bottom line is that the ExactPower trio is among the most expensive power conditioning solutions for home theatre use. Happily, the performance is commensurate with the price, making this one of the very best power conditioning solutions available for audio and video quality.

Provided By

This review, Copyright 2004 Widescreen Review, has been reproduced in its entirety from Issue 86, July 2004 of Widescreen Review, The Essential Home Theatre Resource. Take advantage of our no-risk subscription offer: 13 For $34*1 free trial + 12 monthly issues + 1 special edition + full access pass to WSRs paid subscriber Web sitea 56% savings off the monthly newsstand price (over $43 savings off the cover price)! Phone WSRs Customer Relations Department at 4914 or 888 WSR SUBS, or fax at 2960 to order, or request on-line at: www.WidescreenReview.com/13. Or you can mail your request to: Widescreen Review, 27645 Commerce Center Drive, Temecula, CA 92590. All major credit cards are accepted. * Foreign subscription rates are $40.00US Canada/Mexico, and $75.00US International. Canada/Mexico and International Special Edition Offer Plus Shipping Cost.

Page 3/3