The BHK Signature Preamplifier is the culmination of a lifetime of research and design work on the art of analog preamplification by Bascom King, whose longtime collaborator Arnie Nudell was actively involved in the voicing of the preamp, as he was with the BHK amps. “This is the best sounding preamplifier I have ever designed or heard,” said Bascom, and that’s saying a lot for a man of his experience.
The preamplifier is a full function line stage, featuring five single ended and balanced inputs, a discrete Class-A MOSFET headphone amplifier, all classic through-hole construction, PRP resistors, assignable home theater bypass, and a fully balanced design. Based on a pair of zero feedback 12AU7 current-sourced vacuum tubes feeding a class A MOSFET output stage, the BHK Preamplifier enjoys extreme linearity with a rich and open sound. 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.
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. The Signature Preamplifier uses 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. This unique topology turned out to be the most sonically-transparent level control we have yet heard, and can be controlled from either the front panel rotary controller or the remote control. It 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.
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, and is part of the reason the BHK Signature delivers music in such an effortless fashion.
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 as 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. 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.
Beta units of the BHK Signature Preamplifier will ship during May, with production shipments beginning in June. MSRP is $5999 in the US market; pricing may vary in other markets. Pre-order deposits can be made on the PS Audio website, and the first 50 units will be signed in gold by Bascom H. King.