● Input Voltage Range: 90 to 135 Vrms
Nominal Output Voltage: 1 Amp to 15 Amps
120VRMS with 1% Tolerance
Low-pass Filter: Dynamic, not Passive
Protection: Over Voltage, Over Temperature,
Over Current, Under Voltage
Peak Repetitive Output Current: 46A Peak-to-
Dimensions: 3.5" H x 17" W x 14.2" D
I have long known of the ExactPower unit. Though it works differently than
the PS Audio Power Plant, regulating and correcting power rather than
completely regenerating it, the ExactPower is claimed to have equally major and positive
effects on the sound of one's system.
A number of years back, when the first ExactPower units were released, Mark
Schifter of AV123.com sent me one for evaluation. Alas, it emitted an
unacceptable hum that interfered with my listening. Unable to evaluate music
over the noise, I returned it.
Two years ago,
reviewed the EP15, so we felt it was time for a follow-up, testing the
changes that have been made with the EP15A.
I am happy to report that such noise problems have been
corrected. The ExactPower EP15A operates flawlessly, emitting very little
noise even when channeling tons of current to current-hungry Parasound
Halo JC 1 monoblocks.
My revisit to the ExactPower (which still resides in my system) was
triggered by the need to review those self-same Parasound Halo JC 1
monoblocks (see review in the Secrets archives). These amps require more
power than my P600 Power Plant can deliver. The ExactPower unit can supply
up to 1650 watts of clean power when fed 120 volts from an AC wall socket.
It easily provides enough clean power for the monoblocks and my entire front
When I told Joe Reynolds of Nordost that I was having difficulty reviewing
the Parasounds because of the limitations of my otherwise highly prized P600
Power Plant, he strongly recommended that I contact Quan of Sonic Integrity,
U.S. distributor of ExactPower. Nordost has spent quite awhile evaluating
various power conditioners, regenerators, and the like, and is firmly
convinced of the ExactPower's efficacy.
For those wondering why I didn't simply plug the mighty Parasounds directly
into the wall or something simple like the PS Audio Ultimate Outlet, the
answer is that the sound was unacceptable. Even with a dedicated 30-amp
power line, Oakland's power is too �dirty� to permit optimal listening. The
difference between the sound of these amps and the rest of my components
when switched from wall power to clean power is huge. We're not talking gray
to white; we're talking congested, cacophonous, monochromatic, brittle, and
uncontrolled, to musical. The noise floor drops tremendously, instruments ring
out from an otherwise flat and gray soundstage, the soundstage size increases,
bass gets much fuller and in far more control, highs become listenable, and
the enhanced level of detail throughout the spectrum makes all the
difference. Most of all, instruments and voices begin to take on their
proper color and size perspective. Major, dude, major.
The ExactPower website supplies a fairly complete description of what the
unit can accomplish. In addition to quoting and paraphrasing some of that
information below, I include a conversation with Bill Whitlock, the designer
of the original technology. I also relay information shared by Quan of Sonic
Integrity, the organization that handles the business affairs of ExactPower
The ExactPower unit is capable of supplying 15 amps of clean current through
its eight high quality AC outlets. These are claimed to work substantially
better than �hospital grade� devices. ExactPower claims that the EP15A will
not vary beyond 120 Vrms �
1% when loaded from 1 amp to 15 amps.
If a fault occurs, the unit shuts down and turns back on once the fault is
eliminated. If, for example, an over-current occurs when an amplifier is
being powered up, the EP15A does not shut off; instead, it automatically
switches to wall power. After the over-current event has passed, the unit
switches the outputs back to regulated mode. Having just observed this
phenomenon in action when I powered up the two Parasound monoblocks, I can
attest that the process proceeds smoothly and without the need for user
The ExactPower 15A actively removes high frequency irregularities from the
waveform; it does not filter them. The work is accomplished by a high
efficiency, pulse width modulated power amplifier. Instantaneous correction
and wide bandwidth automatically improve the THD of the waveform. Current is
stored, supplying bursts when needed. Output impedance is significantly
lower than the impedance of the power delivered by the wall receptacle,
allowing equipment to function more efficiently. Custom EMI and RFI filtering
are included. A detachable AC power cord is provided, with the option of
ordering a unit with a Nordost Vishnu. (I powered the unit with Nordost
Valhalla.) Optional brackets are available for mounting in a standard 19�
rack. (I floated the unit on Ganymedes.)
Quoting from the website:
�ExactPower's engineers designed a patent-pending [the U.S. Patent, No.
6,653,824, was granted Nov. 25, 2003], error-free, 'feed forward' technique.
A sophisticated differential comparator circuit monitors incoming AC power
from the wall socket, instantaneously compares it to an internal
amplitude-stabilized AC reference source. It then corrects any imperfections
in the incoming AC signal. That corrected signal, in turn, serves as the
source for a high efficiency power amplifier. Since this technique's speed
is theoretically unlimited, it corrects even high frequency sub-cycle
disturbances without the instabilities that can cause oscillation problems
in functionally comparable but far less sophisticated products.
ExactPower products provide rock-stable 120 volt output with up to 46 amps
of peak-to-peak current capability even when wall socket AC voltage varies
from 90 through 135 volts. In fact, the ExactPower EP15A high current output means
that even large power amplifiers will rarely tax its capabilities.�
A Talk with Bill Whitlock
When I contacted Bill Whitlock, originator of the ExactPower Technology, he
supplied the following bio:
Bill Whitlock has designed pro audio and video electronics and systems for
30 years. In 1989, after seven years with Capitol Records, he became
president of Jensen Transformers. He has become a recognized expert on
system interfacing issues through his writing and teaching. His paper on
balanced interfaces appears in the June 1995 AES Journal, which has become
the most popular ever printed. Other writing includes the popular "Clean
Signals" column for S&VC magazine, three chapters for Glen Ballou's
1500-page "Handbook for Sound Engineers," and numerous magazine articles and
Jensen application notes. Since 1994, he has helped thousands unravel the
mysteries of grounding and signal interfacing by teaching at trade shows,
technical colleges, and professional organizations. Bill holds several
patents including the InGenius(R) balanced input circuit and the
ExactPower(R) waveform-correcting AC power voltage regulator. He is an
active member of the Audio Engineering Society and the Institute of
Electrical and Electronic Engineers.
BW: I'm a well-known lecturer on the subjects of ground loops and system
noises such as hum and buzz, an area that the industry as a whole seems to
treat as some sort of a black art. I have an upcoming tutorial seminar
scheduled for the San Francisco AES the first week of November, and another
for Lighting Dimension International. I deliver about a dozen lectures or
tutorials a year at trade shows, universities, and technical societies. I
also write magazine columns for Sound and Video Contractor and Live Sound,
and have written chapters in textbooks about grounding and interface issues.
It's my specialty niche.
JVS: One difference between the ExactPower unit and the PS Audio Power
Plants is that the latter produce balanced power. The EP15 by itself does
not. Please discuss the issue of balanced power.
BW: Balanced power is largely overrated in terms of its noise-killing
ability. With that being said, the ExactPower people have chosen to make
their own balanced power transformers available as an accessory to the
regulator. (See below.)
If you look at what balanced power does, you can typically expect about 10
dB of noise reduction. It's not a breathtaking reduction in noise. Given
what it costs, that's not a very cost-effective way to fight noise. I
recommend the silver bullet solutions made by the company I own, Jensen
JVS: You work with hum issues. I have a long-standing ground loop in my
system that I usually solve by putting a cheater plug on my Jadis amplifier
or other unbalanced amps I review.
BW: The academically correct way to solve hum problems is to find out where
the problem interface is and then install a ground isolator transformer. Our
Jensen ground isolator transformers don't compromise sound in any way. We
have hundreds of thousands of our transformers in recording facilities �
even on the space shuttle. We are the world's premiere quality audio
JVS: Why would we not want that 10 dB of noise-quieting capacity?
BW: If you don't care about parting with your money, you can buy any
transformer you want. ExactPower, Equitech, Furman and others make them.
They usually list for well over $1000.
Our transformers are passive, go in the signal path, and fully deal with the
JVS: Talk about the differences between your technology and PS Audio's.
BW: The PS Audio Power Plant is a total regenerator � it regenerates 100%
of the power. The problem with doing that is that the unit is inefficient �
it's hot, big, heavy, and costly. We instead convert only what is required to
correct the impurity of the incoming power.
The basis of our patent is that the process is extremely high-speed � it can
actually fix the sine wave on the fly. There's nothing else on the market
that is as fast. Therefore, the ExactPower runs at 90% plus efficiency.
(It's definitely lighter, cooler, and more efficient than the Power Plant.
And it can deliver a lot more power than the mighty and far more costly
ExactPower units do have a peak current limitation, but you have that
limitation from a power cable as well. Every time you add resistance to a
circuit via a wire, you lower the amount of current available.
JVS: The EP15A has four outlets for digital equipment, and four for analog.
What's the difference between them?
BW: The ExactPower unit offers different filtering on analog and digital
outputs. We do this largely to keep the two from talking to each other. The
analog outputs use a combination of common mode and low-pass filtering, a
technology pretty well known in the industry.
JVS: How would I go about correcting the ground loop problem that makes my
BW: We have a troubleshooting guide posted at our website that will help
pinpoint where the problem is. The process involves using shorting plugs
with resistors in them and moving them around. You can make the shorting
plugs on your own by soldering in resistors available at Radio Shack. Or you
can buy them readymade from us.
JVS: Why do you oppose lifting the ground or using cheater plugs?
BW: It's a legal liability and safety issue. There are a number of people
killed each year from ground lifting. If you lift the pin, there's the
possibility that the entire frame of the equipment can become alive at 120
volts. To make matters worse, the 120 volts then travels through all of your
signal interconnects and makes all the other equipment a live 120 volts,
thereby creating an intense electrocution hazard.
Lifting the ground has also been known to cause fires. Let's say there's a
ground on the cable TV connection. The defective piece of equipment will try
to send its current flowing through all the intervening audio cables to try
to get to the grounded cable TV connection. In the process, these high
currents will often set the cables on fire.
While researching my seminars, I've spoken with some product liability
attorneys. They tell me that there have been a number of lawsuits brought by
customers of installers who have used ground lifters to fix ground loop and
JVS: PS Audio touts the Power Plant's ability to lower impedance and help
equipment run more effectively. They also offer a variety of sine wave
manipulations via MultiWave.
BW: We make no attempt to manipulate the sine wave other than to make it pure
and correct the flattop distortion commonly experienced on the top of the
waveform. Because high current devices on power lines especially need the
current at the top of the waveform, voltage tends to be reduced at the top
of sine wave and the wave gets flattened out. This results in voltage drops
in the distribution grid. It's a very common phenomenon, and limits the
amount of power that comes into your home and is available to your
This means your amp, when plugged directly into the wall, will be starved
for power exactly where it wants it most. We restore the sine wave to its
optimal form, enabling your amplifiers and other equipment to get all the
power they need.
I have no bones to pick with PS Audio's product. It is just larger, less
efficient, and more costly than ours.�
More on the ExactPower
After speaking with Bill, I received further clarification from Quan of
Sonic Integrity as to what the ExactPower EP15A offers in the way of power
regulation, conditioning, and protection.
Long-time readers of audiophile reviews will discover that the price of the
EP15A has risen from $1799 to $2499 since the spring of 2002. Besides the
rising costs of material and commerce, the price increase reflects major
changes in EP15A's construction and design. The unit has cleaner lines and
improved metalwork. There have also been many costly changes in the
circuitry to improve performance. The EP15A now offers active surge
protection; it will recognize anything that could potentially damage your
equipment that it can't correct and shut itself down. It can even protect
your equipment against huge voltage swings (brown outs).
The company makes a number of different units in addition to the EP15A. Even
though the EP15A does not supply balanced power, they consider it the best
single solution, especially for those using it with power amplifiers. When
you plug an amplifier into balanced transformer-based units and place large
power demands on the amplifier, you will create a voltage drop in the
amplifier that causes current limiting. This is due to the extra resistance
created by an additional transformer. What this can translate into is sound
that seems slow or sluggish with less pace, rhythm and dynamics.
(It is important to note that the PS Audio Power Plant does not create such
a problem. The Power Plant produces balanced power while regenerating power
totally; it does not create extra resistance. It does, however, have limits
as to how much current it can produce, especially on peaks when current
requirements momentarily balloon.)
For those wanting balanced power, the ExactPower SP15A is a separate
balanced transformer-based unit designed for low-powered front-end gear (CD
player, processor, preamp, DAC, etc.). The SP15 balances power by producing
two 60-volt legs to make 120 volts and running residual noise down the
ground. While the SP15A does provide extra noise-reducing benefits, the
majority of clean power benefits come from the EP. The SP retails for $1099.
ExactPower also manufactures the SPX4. This unit takes balanced power
one-step further. Most balanced units employ only one transformer for all
equipment plugged into them, placing filters between the outlets to reduce
noise. This results in less than perfect noise isolation. The SPX4 provides
a separate 500W transformer for each of its four outlets, resulting in total
and complete isolation. It retails for $1599.
I spent considerable time comparing the ExactPower EP15A to the PS Audio
P600 Power Plant. I listened extensively on many occasions, inviting a
visiting dealer to listen with me at one point, playing many different kinds
of music. The EP15A in fact remains with me, for use during the blind power
cable comparison test Secrets is running in conjunction with the Bay Area
Nordost Valhalla Power Cables powered all components in the chain including
the PS Audio and ExactPower units. Since I don't have a zillion of these
power cables on hand, I had to plug and unplug when moving between units.
Readers who adhere to the belief that power cables do not make a difference
may wonder why I went to the trouble of switching cables on four pieces of
equipment each time.
The long and short of it is that I do hear differences between power cables.
PS Audio's Paul McGowan hears differences, recommends upgrading power cables
on the Power Plant, and manufacturers a variety of power cable models. EP15A
distributor Sonic Integrity also hears differences and makes the Nordost
Vishnu Power Cable available as a purchase option for improved sound. I
stick with the Nordost Valhallas because I think they deliver more extended
and open sound throughout the spectrum with astounding vibrancy and
transparency. Though I acknowledge that I've tried only a fraction of the
after market power cables currently available, the Nordost Valhallas are the
most neutral, revealing, and sonically satisfying power cables I've ever
Because I had to constantly move power cables between two different units in
the cramped space behind my rack, comparing the P600 to the EP15A was no
easy task. The process also necessitated repositioning Styrofoam squares
between power cables and interconnects to minimize interaction. Doing so
does not a relaxed listener make; it most certainly tests one's sonic
memory. While I have done my best to figure out which way was up, if I were
called to testify before Judge and Jury, I'd be tempted to take the Fifth.
What I Heard
Despite their differences in technology and approach, both units do a fine
job. The Power Plant's advantages, in addition to fully balanced, completely
regenerated, voltage-adjustable clean power, include its MultiWave options,
which alter the sine wave and definitely affect the quality of the listening
experience. While the EP15A offers neither balanced power, voltage
adjustment, nor MultiWave, it cleans up the sine wave, uses much less
electricity, runs cooler and more efficiently, and can easily power
amplifiers that tax even the largest, heaviest, and most costly Power Plant
How does that translate sonically? Auditioning the P600 in SIN mode, without
utilizing MultiWave, I found that the EP15A gave Ariana Savall's exquisite
soprano and harp on Bella Terra a bit more life. There were beautiful
overtones to the harp, a glow to the sound, with very natural edges on
everything. The sound was also remarkable quiet.
On Rachmaninoff's Symphonic Dances (a Reference Recording disc that never
fails to stun listeners), I initially found the EP15A's bass leaner and less impactful, yet paradoxically more in control. Was this because less bass
meant less room interaction? Did it mean that what I considered the P600's
extra slam was actually extra smudge? Going back and forth between the
units, I felt the P600 had more snap, but the ExactPower sounded less
bloated and more in control in the bass. If it had leaner bass, it was
The dealer who dropped by days later (who does not sell either of these
products) favored the P600. He thought the sound more three-dimensional, the
soundstage larger, and the percussion more correctly positioned and
stronger. I continued to sense more clarity from the EP15A.
In a subsequent listening session, I pulled out my favorite Terry Evans
�Puttin' it Down� track from Blues No More and the first movement on Michael Tilson Thomas' hybrid SACD of Mahler's dynamic
Symphony No. 3. I also
revisited the Rachmaninoff. Perhaps the Nordost power cables, not fully
broken in before, needed the extra time, because my feelings were now
Listening to the last few minutes of Mahler's massive first movement, I
actually heard more bass impact from the ExactPower. While I personally
continue to favor the P600's P-1 MultiWave setting for the outstanding
clarity, three-dimensionality, and bass slam it lends to recordings (and
others complain that the results sound artificial with highs overly etched
and midrange slightly constricted), I thought the P600 in normal SIN setting
sounded a little less crisp and clear than the EP15A. Instead of delivering
leaner sound, might the ExactPower render sound just a bit more exact?
The bottom line is that you cannot go wrong with either unit. If you prefer
the sound of the Power Plant and have or may eventually upgrade to multiple
power hungry amps, you will need multiple Power Plants and power cables,
silent air conditioning, and/or a very large room, and enough money to pay a
substantial electric bill. The ExactPower EP15A, with its 1650-watt maximum
capacity and 90% efficiency, presents a more flexible and cost-effective
In the end, it's the difference between oranges and grapefruits dyed the
same color. Both units have their strengths. Beyond the differences I hear
between them when using premium components, cabling and supports �
differences that will be less noticeable (albeit nonetheless present) on
more modest systems � lies the reality that both units perform wonders by
transforming sonic hash into music.
The most significant choice you can make is whether you
compromise your listening and viewing pleasure with dirty power, or whether
you will allow yourself more of the joy your gear can deliver. If you
opt for clean power, the unique attributes of the Exact Power
EP15A make audition indispensable.
- Jason Victor Serinus -
Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII DAC/Preamp
Theta Carmen II transport
Jadis Defy 7 Mk III or IV modified with a Siltech silver harness
Parasound Halo JC 1 monoblocks
Talon Khorus X speakers MK. II (with latest modifications and Bybee filters
on woofers and tweeters)
Nordost Valhalla single-ended and balanced interconnects and balanced
Nordost Valhalla bi-wired speaker cable
Nordost Silver Shadow digital interconnect for DVD-V
Nordost Valhalla Power Cables
Also on hand and sometimes used:
Interconnects: WireWorld Gold Eclipse 5 and Gold Starlight 5 digital,
Harmonic Tech Magic One, Acoustic Zen Silver Reference II balanced, and
Nirvana BNC-terminated digital.
Power cables: Elrod EPS Signature 2 and 3 plus EPS 1, 2, and 3; WireWorld
Silver Electra 5, PS Audio X-treme Statement, Harmonic Tech, and AudioPrism
PS Audio P600 Power Plant power synthesizer with MultiWave II
PS Audio Ultimate Outlet; PS Audio Power Ports
Michael Green Deluxe Ultrarack, Basic Racks and Corner Tunes
Ganymede supports in main digital chain and under speakers
Michael Green Audiopoints, and Black Diamond Racing Cones elsewhere
Shakti stones on amp, Theta, and transport
Stillpoints ERS EMI/RFI sheets on most components
Bedini Dual Beam Ultraclarifier
Audioprism CD Stoplight
Marigo Signature Mat for use atop CDs
Ayre demagnetizing CD and the original Sheffield/XLO demagnetizing and
� Copyright 2004 Secrets of Home Theater & High Fidelity