PS Audio is one of the more respected names in the audiophile arena. Even a
cursory inventory of equipment owned by longtime Bay Area audiophiles turns
up a 15-year old PS Audio preamp in one home (still used in the downstairs
system), and an early, much loved amp in another. I continue to use and
admire the P600 Power Plant, whose original P300 precursor received one
publication's coveted "Product of the Year" award back in 2000. I also use
the PS Audio Ultimate Outlet and Power Port wall outlets.
In a design field populated by an unholy conglomeration of music lovers,
hustlers, eccentrics, undisputed geniuses, anti-social geeks, egomaniacs,
visionaries, and pretenders to the throne, Paul McGowan stands out as one of
the most likeable and respectable of the lot.
The man clearly loves enriching people's lives with
music as much as he enjoys interacting with them. I have always found PS
Audio's customer service department a joy to work with, and Paul himself
readily accessible and willing to assist. Anyone who owns PS Audio gear and
has found their system suddenly on the blink a week before that long awaited
guest is finally scheduled to come over for a first listen will find
themselves grateful for the attention the company will pay to their plight.
When I approached Paul at CES 2005 about reviewing one of his new amps, he
knew full well that I in general prefer the sound of tubes over that of
solid state. He nonetheless expressed confidence in the sound of his new
GCA-250, the 250W model in PS Audio's line of three GCA gain cell amplifiers
with power ratings of 100, 250, and 500W. The amp arrived some months back,
and has sat in cue for awhile as I've slowly moved through the backlog of
equipment awaiting review.
The GCA-250 is a dual mono, class D (digital switching) amplifier. With one
pair of single-ended RCA inputs, one pair balanced XLR inputs, and
work-like-a-dream-PS Audio locking speaker binding posts, the marketing info
touts many benefits. These include, besides PS Audio's Gain Cell technology,
little or no heat – a MAJOR factor in tight quarters where the heat of tube
equipment makes listening uncomfortable if not downright impossible in the
warmer months – extremely low noise, rock solid image, deep bass, open and
spacious sound, ultra low distortion, and effortless performance with "any"
loudspeaker. On paper, at least, the GCA sounds like one of the better buys
in high-end audio.
PS Audio offers a 30-day in-home trial with a full refund minus shipping.
Their transferable warranty covers five years if the warranty card is
returned within 90 days of purchase; otherwise, three years, with an
additional two-year extension for $50. To qualify for the extended warranty,
you must purchase from an authorized dealer and submit a written receipt.
The Inner Workings
PS Audio has achieved fame in my book for the simplicity of its online
technical discussions. Rather than regurgitate it all, I shall concentrate
on a few points, and invite you to check out the rest by clicking on a host
of links listed at
First, this is a true dual mono design. Based on PS
Audio's new Gain Cell technology each GCA contains two completely
independent gain cells and two equally independent mono SDAT power modules.
Only the power cable is shared.
Second, the GCA series couples analog Gain Cell Technology at the input
stage to its SDAT (Super Digital Amplifier Technology) Class-D power output
stage. It uses "a fully independent and regulated switching power supply to
feed each of the power modules, virtually eliminating any need for input
power transformers and heavy magnetics." MOSFET transistors inside the
analog power module operate upwards of 85% efficiency.
Note that the GCA is a hybrid design. While someone who reviewed a product
in the company's GCC series for another website seems to have inferred that
the amp's input stage is analog and the output stage is digital, that is not
actually the case. The information on the PS Audio website is a little
confusing, so I wrote to Paul McGowan for an explanation, and he sent the
"The GCA-250 is a hybrid product in the sense that the input stage is pure
class A analog Gain Cell and the output stage is a class D switching power
amplifier. Hybrid because it's two distinctly different technologies married
"When I switch back and forth with the usage of a digital output stage and
an all-analog output stage I use the term 'digital' because people are used
to the term and it helps them relate to what we're doing. Strictly speaking,
it's not a digital stage; in fact, it's all analog.
"Pulse width modulation [PWM] switches the output transistors on and off in
varying lengths of time – thus the use of the term 'digital' because the
output stage is a series of on and offs. However, in reality, a true digital
system incorporates some type of coding scheme of ons and offs that are
later interpreted by a computer-like device and then converted to analog.
"Not so with PWM. The varying ons and offs are converted directly to analog
with a simple filter that rolls off the transitions. This is possible
because it's a 100% analog system to start with."
PS Audio touts their gain cell as "about the most perfect gain block ever
invented." Called the "heart and soul" of every GCA product, a gain cell is
"a single block of analog gain in a potted module, direct coupled from input
to output in one of the cleanest, purest audio paths ever devised."
Gain Cell specifications include:
>80dB input common mode rejection
>0.005% THD+N @1 volt rms
>-100dB SN A weighted
Gain adjustable from -100dB to +30dB
Step resolution >0.001dB
Input impedance 47 kOhms for both +/- inputs
Output impedance 100 Ohms for both +/- outputs (Note: This is the impedance
for the Gain Cell output connections, not the output impedance at the
Boasting perfect linearity, with the same voltage in and out, PS Audio
claims "effortless sound regardless of volume. From micro dynamics to macro
dynamics, this amplifier sounds the same on the softest passages to the
loudest orchestral crescendos."
Please read on to discover how this translates into sound quality.
I replaced my reference Jadis with the GCA-250. Noting that the manual
affirms that the amplifier can benefit from "aftermarket isolation devices
such as cones, spikes, and Sorbothane pads," I chose Ganymede ball bearing
supports, which to my ears provide far more vibration isolation without
damping highs than other supports I've tried.
Again noting that PS Audio's own words, "While the supplied power cable is
adequate for the task it is not going to provide the best performance"
reflect my own experience, I installed my reference Nordost Valhalla power
cable. In my experience, the Valhalla allows components to achieve far more
of their full potential than the single PS Audio xStream Power cable I have
PS Audio recommends the use of power conditioning equipment "such as a PS
Audio Power Plant, UPC-200, or any of the Ultimate Outlet or Power director
series from PS." They do not recommend other AC filter power conditioners,
claiming, "Most of these will 'bleach' the sound and rob the music or video
soundtrack of life and dynamics. If you do not us PS Audio Power
Conditioning equipment, you would be advised to plug the GCA Power amplifier
directly into the AC wall receptacle."
No problem. I wouldn't even think of plugging the amp directly into the
wall, knowing the sonic compromises I've experienced when doing so. Given
how little current the GCA-250 draws, plugging it into the P600 Power Plant
was a piece of cake.
Interconnects and speaker cable were also Nordost Valhalla. The preamp was
my reference Theta Gen. VIII DAC/preamp, whose specs seem totally compatible
with the GCA-250s.
At first I tried the amp's single-ended inputs.
Then, switching to the balanced XLRs, and adjusting the simple input switch
on the back of the amp accordingly, I confirmed PS Audio's assertion that "a
balanced XLR type of output allows the lowest noise connection between
preamp and power amp, and allows owners to take advantage of the high common
mode rejection characteristics found in the Gain Cell of the GCA Series
Power Amplifier. Be sure to use a high quality well shielded and well
regarded interconnect for this critical link."
I stuck with balanced inputs for the duration of my listening experience.
I also kept the amp powered on throughout the five to six weeks I spent
auditioning it. The company claims that keeping the amp on insures that its
internal AC capacitors stay working properly, draws a negligible 40 W
current (well, more like 65 through the inefficient Power Plant), and does
not shorten lifespan. Since the amp really does produce little heat, and the
intensity of the front panel's electric blue logo can be set to medium or
shut off entirely, I found keeping it on relatively painless.
Here to Go to Part II.