PS Audio BHK Signature 250 User Manual

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POWER AMPLIFIERS

ascom H. King is a hi-fi legend.
If you haven’t heard of him, you
may have come across some of
the amplifiers he’s designed for
brands that include Constellation

Audio, Marantz, Infinity and Conrad Johnson.

His latest creation was commissioned
by Boulder, Colorado-based PS Audio, a
company with roots in innovative audio
stretching back to the early 1970s. The
new amplifier (two, actually, if you count
in the monoblock version) is notable for
several reasons.

Firstly, it’s the first amplifier deemed
good enough by King to bear his initials
(BHK). Secondly, it’s a hybrid design
that links a valve-based input stage to
a MOSFET output stage, at a time when
much of the focus in amplifier development
is focussed on variations on the Class D,
switched-mode power supply genre.

It’s also the first power amplifier from
the PS Audio since the now defunct HCA-2
(an ahead-of-its time Class D switch-mode
amp) and the pure solid-state Classic 250,
both dating back to the early 2000s, as
well as the GCA Series amps, which inci

­dentally were also hybrids, linking a
Class A solid state input stage to a Class D
power output stage.

It’s interesting then that the amplifier
now being touted by PS Audio as almost
without peer features a tube-based input
stage, combined with a solid-state output
stage. Does it tell you something about
Class D switch-mode designs? I think
it does …

What is indisputable is that Bascom
H. King has seen it all and done it all in
a career spanning half a century. And if
King believes that the BHK Signature 250
stereo power amplifier represents every-

thing he’s been aspiring too, then the
chances are it’s going to be something
special.

Having been spoilt by a succession of
new-generation, lightweight switch-mode
amplifiers from the likes of Wadia, Classé
and McIntosh Labs, manhandling the PS
Audio into our listening room and onto a
spike-coupled plinth felt like a blast from
the past. At close on 37 kg it’s a hefty
beast that can make grown men cry, and
chiropractors clap their hands in glee.

The casework reflects PS Audio’s current
design language, which is attractive in a
form-follows-function kind of way. At least
the heatsinking is internal and the corners
are rounded, so you don’t end up with
post-installation bleeding knuckles …

The all-metal enclosure is crowned by
a glossy acrylic top, while substantial,
isolating feet locate it sturdily on what

B

PS Audio BHK Signature 250

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POWER AMPLIFIERS

had better be a strong, solid surface.
Those familiar with PS Audio components
will recognise the blue square logo on the
otherwise plain faceplate that acts both
as a power-on switch and indicator light.

Things get a little busier at the rear:
a choice of RCA single-ended or XLR
balanced inputs, an IEC power socket, and
two sets of binding posts for each channel,
which will please those with dual runs of
fat speaker cables for bi-wiring purposes.

The overall impression is smart and
upper class, with a definite emphasis on
the kind of solid, reassuring engineering
that speaks of care and quality. There
aren’t any frills, because there’s no need
for them.

According to PS Audio, the BHK Signature’s
valve input stage features matched pairs
of Russian-made Genelax Gold Lion 6922
triodes that are self-biased with constant
current and high voltage. Without the need
for introducing negative feedback, timing
and phase distortion are no longer an issue,
while the valves remain electrically
isolated from the power output stage.

However, tubes can’t offer the power,
speed and authority of solid state designs
— which is why the BHK signature adopts
a hybrid approach, benefiting from the
purity, delicacy and richness of the valve
input stage, while delivering it with the
punch, gusto and impetus of a MOSFET­based solid-state output stage.

PS Audio claims MOSFETs sound better
than bipolar transistors, and sound more
like tubes than transistors, making for
an easier sonic transition from tube to
solid state. The BHK Signature employs
low-distortion N-type MOSFETs only in
the interests of lucidity and consistency.

While it is a hybrid power amplifier,
the BHK Signature treats the input stage
and output stage as two independent
entities, each with its own power supply
and power regulation. Particular attention
was paid to signal path purity, with passive
circuit components hand-selected for
performance and sonic integrity, and then
hand-soldered onto the circuit boards —
there are no surface-mounted parts.

The result is an amplifier featuring
a level of bespoke attention to detail

Power output per channel ........................250 watts (8 ohms), 500 watts (4 ohms)

Frequency response ..................................................10 Hz – 20 kHz (± 0,1 dB)

Signal-to-noise ratio ............................................... <-85 dBV (100 Hz – 20 kHz)

Inputs ...............................................................1x stereo XLR, 1x stereo RCA

Outputs ..........................................2x gold-plated binding post sets per channel

Power consumption ..................................... 75 watts (standby), 175 watts (idle)

Dimensions (WxHxD) .......................................................434 x 221 x 356 mm

Weight ........................................................................................ 37,6 kg

Price ........................................................................................ R113 000

Verdict

Effortless control and authority allow a fleet-footed, engaging delivery without imposing
a specific sonic signature. Purity meets power to deliver unfettered musicality.

Supplied by PL Computer Services
082 578-5708

e-Mail [e-mail]

Website www.psaudio.com

OUR RATING: 92 / 100

VITAL STATS

unusual even at much higher price points,
and with a focus on absolute fidelity that
suggests exceptional musicality. The best
way to find out? Take a listen!

The BHK Signature reviewed here arrived
brand new — even the official importer
had not laid eyes on it — and I proceeded
to run the amplifier in, with sporadic
listening sessions confirming that progress
was indeed being made. However, let me
warn any prospective buyers up front: this
amp needs time to settle in.

In my opinion, 200 hours should be the
absolute minimum before you can expect
the BHK Signature to approach anything
close to its full potential, even though the
PS Audio team recommend 100 hours. By
the time I finally had to send the power
amp back, it had amassed around 320 hours,
and I felt that it was still improving.

Thus, the comments in this review
should be read in that context, with most
of the listening notes compiled at about
250 hours or so. They were balmy hours,

here is a gentle giant of an amplifier that

pays close, deferent attention to fine details

and nuances without relinquishing any

control or focus. It’s also very, very quick