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PS AUDIO - BHK Signature 250 Stereo Power Amp

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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

Outputs 250Wpc Into 8 Ohms: Fully Balanced BHK Signature 250 Stereo Power Amp Features Zero-Loss Vacuum-Tube Input Stage, Separate Isolated Analog Power Supplies, MOSFET Regulators

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.

“This amp is that rare Holy Grail whose sensible price belies its astounding performance. Hand built in America, it may well be your final amplifier purchase. Enthusiastically recommended!”

—Eric Neff, Hi-Fi+

"...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.

    1x Pair RCA (Unbalanced)
    1x Pair XLR (Balanced)
Outputs: 2prs per channel
DC Trigger Input: 3.5mm @ 5-15VDC
Power Consumption:
    Ready: 75 Watts
    Idle: 175 Watts
    8Ω: 850 Watts
    4Ω: 1600 Watts
Gain: 30.5dB (±0.5dB)
Sensitivity: 1.2V
Noise: Below -85dBV (100-20kHz)
Input impedance:
    Unbalanced: 100kΩ
    Balanced: 200kΩ
Output Impedance: <0.1Ω (@50Hz, 2.8VRMS)
Frequency Response:
    10Hz - 20kHz (±0.1dB)
    10Hz - 200KHz (+0.1/-3.0dB)
THD: 20-20KHz: <0.1% ([email protected]Ω)
Output Power (1kHz @ 1%THD):
    8Ω: 250W (300W)
    4Ω: 500W (600W)
    2Ω: Stable for musical transients
Input Voltage: 120VAC @ 60Hz
    4x 10 Amp Fast Blow H-Rated 5x20mm (Rail Fuses)
    1x 1.6 Amp Slow Blow H-rated 5x20mm
    1x 10 Amp Slow Blow H-rated 5x20mm
Accessories Included US (NEMA 5-15P) (all versions)
Warranty: 3 years parts and labor on unit, 1 year vacuum tubes
Weight: 83 lbs.
Dimensions (WHD): 17.1" x 8.7" x 15

Owner's Reference (PDF, 517 KB)

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