Created By Legendary Designer Bascom H. King: Reference-Setting PS Audio BHK Signature 250 Stereo Power Amplifier Provides Wowing Levels of Musicality, Openness, and Dynamics
PS Audio's breathtaking and breathtakingly great BHK Signature 250 power amplifier isn't shy about its intended purpose and status. Created to be one of the very best power amps in the world, and the end-result of legendary amplifier designer Bascom H. King's 40-year quest for optimal musical reproduction, BHK Signature 250 is available for about one-tenth the cost of any other King-helmed stereo model. Featuring a zero-loss vacuum-tube input stage coupled to a high-bias differentially balanced MOSFET output, this American-made sonic magnum opus delivers glorious levels of musicality, openness, tonal richness, accuracy, immediacy, dynamics, and liveliness. Outputting a mammoth 250WPc into 8 ohms (500Wpc into 4 ohms), BHK Signature 250 drives, controls, and powers nearly each and every loudspeaker with complete authority.
Fully balanced with separate isolated analog power supplies (one for the vacuum input stage, one for the N-channel MOSFET output stage), this no-expense-spared hybrid power amplifier is built to impress with complete through-hole construction (no surface-mounted parts), separate and discrete MOSFET regulators, hand-selected passive parts, and even solid copper gold-plated binding posts. The practical upshot of these decisions relates to the textures, nuances, transients, timing, and information you will hear – and recordings you will experience like never before. Free of signal degradation, BHK Signature 250 passes through even the most minuscule musical cues with phenomenal clarity and truthfulness, and deposits them amidst soundstages that stretch far, deep, and wide. No other hybrid stereo design compares. 100% Music Direct Guaranteed.
"...A powerful, nimble-sounding amplifier that immediately drew me in with fast, punchy, tight bass; rich, liquid mids; and delicate, transparent highs—all effectively well integrated into a coherent whole."
– Michael Fremer, Stereophile
Zero-Loss Input Stage to Preserve the Most Finite Musical Detail
The connection between preamplifier and power amplifier is critical, for
it is at this junction where most essential musical details are
easily lost. When it comes to preserving music's finest nuances, nothing
in a power amplifier's design is more important than its input
stage. In BHK Signature, a vacuum tube serves as the perfect
interface between the preamplifier and the massive power output stage
inside BHK Signature. The input stage's seemingly impossible task of
passing both delicate and powerful musical information without loss is
made possible by massive numbers of free-flowing electrons traveling
within BHK's vacuum tube—electrons quantities that are not to be found
in transistors. The vacuum tube is unique amongst amplification devices:
It boils an abundance of free electrons in empty space while modern
devices pull fixed numbers through solids. A tube's high voltage, empty
space, rich numbers of electrons, and connection through unattached
fields preserve details lost in the solidity of silicon. The BHK Signature input features a classic triode vacuum tube in a
modern configuration. Hand-matched pairs of Russian Gold Lion 6922s are
self-biased with constant current and high voltage, free of timing and
phase distortion without the use of negative feedback. They provide the
ideal interface between the delicate musical transitions output by the
DAC or preamplifier, and are electrically isolated from the BHK power
output stage which is connected to the loudspeaker.
"Well, simply put the BHK 250 rocks and does so with a nimble presence that puts the music in the room with you. I can't recommend the BHK 250 enough."
– Dave Clark, Positive Feedback
Best-of-Both World Hybrid Design, MOSFET Outputs for Degradation-Free Playback
The hybrid approach used in BHK Signature takes advantage of the best
traits technology offers, unavailable in traditional solid state or tube
designs. While vacuum tubes are the perfect input stage, they cannot
make the same claim on a power amplifier's output. Conversely,
solid-state designs are correct for output stages, but suffer when used
as inputs. A hybrid approach takes advantage of the best in both
disciplines. A power amplifier connects its reservoir of energy to the
loudspeaker through a type of valve controlled by the input stage. If
the input stage has done a good job of preserving music's subtle
details, textures, timing, and phase information, transferring it
without loss to the power stage and eventually the loudspeakers is best
handled by a tube-like solid state device known as a MOSFET. MOSFETs
handle power without the additional circuitry needed by tube power
amplifiers, and sound better than tubes or their solid-state
alternatives, bipolar transistors. Not all MOSFETs are the same, and
their differences are characterized by their relationship with the input
signal and power supply driving them: N-types for the positive going
signals, P-types for negative. N-types have lower distortion and perform
better than P-types. Despite this anomaly, most power amplifier designs
use both types of transistor in a configuration known as complementary
symmetry. BHK takes a different approach, and avoids the problem of
uneven performance between N and P devices. Using only N-Channel MOSFETS
in its output stage, BHK produces a near-perfect balanced waveform
without the degradation inherent in a complementary design.
No-Expenses-Spared Build Quality Extends to Through-Hole Construction
Work on BHK Signature began in 2014 with the goal of building one of the
top five power amplifiers in the world, regardless of price. Bascom H.
King took the charge under the condition he be permitted to design and
build the amplifier his way. Starting with a clean slate, he reimagined
traditional transistor and tube-based amplifiers as a hybrid, with
vacuum tubes on its input and transistors on its output, an idea he
invented 30 years ago. In 1979, King designed the Infinity Class A, the
world's first hybrid power amplifier. J. Gordon Holt, founder of Stereophile
magazine wrote: "It is the best sounding amplifier I have ever heard."
To maximize the benefits of the two amplification topologies inside the
amplifier, it should be built as if it were two separate systems, each
with their own power supply tailored to fit. Thus, BHK has two power
transformers, one for the vacuum-tube input stage, the other for the
MOSFET power output stage. Separate and discrete MOSFET regulators are
used throughout to preserve details found in the music and keep noise
levels to a minimum. Each passive component is hand-selected to provide
the cleanest path possible. PRP resistors, film and foil Rel Caps, and
the finest-sounding parts possible are hand-soldered onto BHK's circuit
boards. King insisted no surface mount parts be used in the signal path.
No expense was spared. Even the output connectors are custom-machined
out of copper, then polished and gold-plated for best connection.