PS Audio BHK Signature Preamp + BHK Signature 250 Poweramp

$19,990

Brand PS Audio

Introducing one of the most remarkable musical instruments in the world, the BHK Signature Preamplifier. This exceptionally built vacuum tube preamplifier opens up the music and reveals nuances, life and space not previously heard on your system. It is the perfect interface between your sources and power amplifier. Designed by Bascom H. King, the BHK Signature distills Bascom’s 50 plus years of high-end audio design experience into a single masterpiece of audio amplification. “This is the best sounding preamplifier I have ever designed or heard,” and that’s saying a lot for a man of Bascom’s experience. Preamplifiers play a critical role in any separates audio system, strategically positioned between sources of music: CD players, phono preamps, DACs, tape recorders and tuners – and your power amplifier – the preamp serves essential roles of control and isolation. Control is simple in concept, but extraordinarily difficult to design in an acoustically transparent manner. Control duties such as input switching, volume, balance, and amplification can place unwanted acoustic thumbprints on the music if not designed with extraordinary care. The challenge in any design is to do as little damage to music’s purity as possible. Details on how each section of the BHK Signature executes control with minimal sonic impact can be found in the Overview section on this page.  

The single most important element of design

Over Bascom’s half century of designing high-end audio products for companies like Infinity, Marantz, Conrad Johnson, Counterpoint,  Constellation Audio, and now PS Audio, one overriding principle has dominated all others when sonic compromise isn’t an option: use of a vacuum tube on the input. The isolation and near-perfect linearity of a well designed vacuum tube input stage cannot be duplicated by solid state means, though many have tried.

Vacuum tubes are simply more convincing and musically accurate than any other input configuration I have ever tried,” said Bascom, and the BHK Signature preamplifier is demonstrative of this observation.

The BHK Signature Preamplifier features two 12AU7 dual triode vacuum tubes in the input stage that act as a zero feedback balanced input amplification pair. A unique self biasing constant current source and user selectable switch combination allows those who like to roll their own tube selections to place any acceptable 6, 7 or 12 series vacuum tubes inside the preamp. The twin hand-selected vacuum tubes that ship with the BHK are the preferred models we recommend and use in PS Audio’s Music Room One reference system.

It all starts at the input

The BHK Signature Preamplifier features 5 identical balanced and single ended inputs. Each of the inputs, whether single ended (RCA) or balanced (XLR) are immediately converted to a pure balanced signal by the dual triode vacuum tube for lowest distortion, highest linearity performance. Input switching is accomplished through hand-selected double-pole double-throw, gold plated relays that we’ve chosen for their sonic neutrality. The signals, once selected, are passed directly the revolutionary new multi-stage attenuator controlling both volume and balance.

If the preamp is going to be part of a home theater system controlling the main left and right channels, each input can be user-assigned as a home theater bypass.

Controlling the volume is a critical task

Perhaps the most difficult challenge facing preamp designers is the volume control. Simple in concept, controlling the level fed to your power amplifier, without damaging the sound, can be one of the most daunting design tasks. During high-end audio’s formative years it had become standard practice to incorporate a high quality rotary potentiometer to control the volume. Over the years designers discovered even the finest of those controls imparted an unacceptable sonic thumbprint, robbing the music of life and openness. Various schemes at removing the potentiometer’s degradation were tried with varying degrees of success. They included stepped attenuators, conductive plastic impedance elements, electronic gain circuits, relay, CMOS switching, and a host of other innovative ideas.

Bascom King decided to try a fresh and novel approach in the Signature preamplifier. A combination of an input stepped attenuator, built around the highest quality passive components for course volume adjustments, coupled with controlling the actual gain of the vacuum tube for finer steps, turned out to be the most sonically transparent level control we have yet heard. This unique topology, which can be controlled from either the front panel rotary controller or the remote control, provides the lowest possible impact on music passing through–and is one of the primary reasons the BHK Signature presents music in such a revealing, open manner.

Once amplified the signal must interface with the outside world

A designer’s best efforts at preamplification can be wasted if the interface between the preamp’s output, the interconnecting cables, and the receiving power amplifier are not optimized for lowest impact, best performance. Cable interactions and power amp input stages can test the mettle of any design, so it is critical a preamp’s output stage provide a high current, class A, low impedance design. The BHK Signature preamplifier output stage is a high-bias class A MOSFET design that is unaffected by cable and power amplifier interface challenges. Simultaneous connections of both single ended (RCA) and balanced (XLR) outputs have minimal impact on the delicate vacuum tube gain stage and provide remarkable isolation between source components and the power amplifier of your system.

This high current low impedance Class A output stage is part of the reason the BHK Signature delivers music in such an effortless fashion. One of the first qualities owners of the preamplifier will appreciate is its remarkable ability to isolate source and control from the power amplifier – and one of the principle factors in the BHK Signatures extraordinary life-like presentation of music, preserving every nuance in your media.

The headphone amplifier

Not every system is based exclusively around the loudspeaker and power amplifier. Many of today’s finest systems incorporate high-end headphones as either an adjunct to the main system or are the main system. Built into the BHK Signature is a state of the art headphone amplifier capable of delivering near perfect performance for any high-end headphone. Take the time to click on the video tab above these words to hear what designer King has to say about his design philosophies when it comes to headphones. The BHK Signature headphone amplifier was borne from years of work on such products as the Audeze King (designed by Bascom) among others. Extremely low–near zero–output impedance, zero feedback, transformer coupled, MOSFET and discrete, the internal headphone amplifier inside the BHK Signature is a tour de force that honors the music the designer worked so hard to preserve.

Specifications:

Physical

Unit Weight 22 lbs [13.5 kg]
Unit Dimensions 14” x 17” x 4” [ 36cm x 43cm x 10cm]
Shipping Weight 31 lbs [19 kg]
Shipping Dimensions 20.5”x 24” x 10” [52cm x 61cm x 25cm]

Power requirements

Input Power Model specific 100VAC, 120VAC, or 230VAC 50 or 60Hz
Power Consumption 60W

Audio inputs

Coaxial RCA single ended (5), XLR Balanced (5)

Audio Outputs

Coaxial RCA single ended (2), XLR Balanced (2)

Analog Audio Output

Connector RCA/XLR Unbalanced /Balanced (X2)
Output level 4.0 Vrms
Output Impedance <100Ω
Frequency Response 20-20KHz +/- 0.1dB
THD+N @ 1KHz (full scale) <0.03%
Bandwidth -3dB 0.1Hz - 200kHz

DC Triggers

+12V 2

 

BHK Signature 250 Stereo Amplifier

A forty year quest for musical perfection

“The first amplifier I gave up a lifetime obsession with tubes for” Arnie Nudell, founder, Infinity Systems.

Have you ever wanted to own the finest stereo amplifiers in the world but were scared off by a six-figure price tag? All that is about to change. The BHK Signature Series power amplifier is a stunning achievement in power amplification and Bascom H. King’s finest work, unequaled in performance at any price. Power amplifiers are the make-or-break component in the music reproduction chain. Everything in your system funnels into this critical component; anything lost can never be recovered.  The BHK Signature features a zero-loss vacuum tube input stage coupled to a high bias differentially balanced MOSFET output. This amplifier has few rivals at any price and, in terms of sheer musicality, openness, tonal richness and accuracy, none.  

Features:

  • Zero-loss vacuum tube input stage
  • Differentially coupled balanced MOSFET output stage
  • All through hole construction (no surface mount parts)
  • RCA Single ended input
  • XLR balanced input
  • 250 watts per channel 8Ω Signature
  • 500 watts per channel 4Ω Signature
  • 2Ω stable Signature 250 stereo
  • Less than 0.1% thd 20Hz to 20kHz at rated power
  • Damping factor 100 for excellent loudspeaker control
  • Front panel standby button for vacuum tube input
  • -3dB greater than 200kHz
  • Dual, custom, solid copper, gold plated output binding posts
  • Fully balanced from input to output
  • 38 kgs
  • Input 12 volt trigger
  • Easy access for tubes

Specifications:

 

BHK Signature 250 Stereo and BHK Signature 300 Mono

Unit Weight 38 kgs
Unit Dimensions 17.1” x 8.7” x 14” Chassis only. 15" deep including connectors.
Shipping Weight 92 lbs
Shipping Dimensions 21”x 13” x 19”
Color Options Black
Silver
Voltage Options
Factory set only
Japan 100V
North America 120V
Europe/Asia/Australia/New Zealand 230V
Mains Power Inputs IEC C14
Fuse Compliment all Countries 4 - 10 amp fast blow H-Rated 5x20mm Rail Fuses
Fuse Compliment Mains 100vac Countries
1 - 2 amp slow blow H-rated 5x20mm
1 - 12 amp slow blow H-rated 5x20mm
120vac Countries
1 - 1.6 amp slow blow H-rated 5x20mm
1 - 10 amp slow blow H-rated 5x20mm
230vac Countries
1 - 1 amp slow blow H-rated 5x20mm
1 - 5 amp slow blow H-rated 5x20mm
Accessories Included US (NEMA 5-15P) (all versions)
Schuko (CEE7/7) (230V version)
UK (BS 1363) (230V version)
Audio Inputs RCA (Unbalanced)
XLR (Balanced)
Speaker Outputs Signature 250 Gold plated copper binding posts (2 pair per channel)
Speaker Outputs Signature 300 Gold plated copper binding posts (2 pair)
Other DC Trigger Input
3.5mm 5-15VDC
Warranty 3 years parts and labor on unit
1 year on vacuum tube

Power Consumption

@Ready 75 Watts
@Idle 175 Watts
@Rated power 8Ω 850 Watts
@Rated power 4Ω 1600 Watts

Signal

Gain 30.5dB +/-0.5dB
Sensitivity for rated output power of 250 watts into 8Ω 1.3V
Noise 100-20KHz <-85dBV
Input impedance Signature 250 stereo Unbalanced 100KΩ
Balanced 200KΩ
Input impedance Signature 300 mono Unbalanced 50KΩ
Balanced 100KΩ
Output Impedance 50Hz, 2.8VRMS <0.1Ω
Frequency Response @2.8VRMS
10Hz – 20KHz +/- 0.1dB
10Hz – 200KHz +0.1/-3.0dB

THD

1KHz, 1W/8Ω <0.01%
20-20KHz, 1W/8Ω <0.1%
1KHz, 200W/8Ω < 0.1% (120VAC Mains input)
1KHz, 400W/4Ω < 0.1% (120VAC Mains input)

Signature 250 Stereo Amplifier

Output Power

Both channels driven 120vac mains, 1kHz, 1% THD
8Ω 250W minimum
4Ω 500W minimum
2Ω Stable for musical transients

Signature 300 Mono Amplifier

Output Power

120vac mains, 1kHz, 1% THD
8Ω 300W minimum
4Ω 600W minimum
2Ω 1000W
 
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