The more than 50 years in audio of Bascom H. King, the BHK behind PS Audio’s BHK Signature preamplifier, extend back past the entire 43 years of PS Audio itself. King has been a reviewer, designer, and technical consultant -- and, in that last role (full disclosure here), measures preamplifiers and power amplifiers for SoundStage!. (Check out PS Audio’s website for videos of Bascom King’s thoughts on his creations and on the high end in general.)
Several years ago, Paul McGowan, the P in PS Audio, was growing dissatisfied with the progress being made on a new power-amp design he hoped would be considered among the world’s best. Following the advice of his longtime friend and collaborator, Arnie Nudell, founder of Infinity Systems, McGowan contacted King, who agreed to be involved in the project on the condition that it be a hybrid design that included a tubed input stage. The fruits of their efforts include PS Audio’s BHK Signature preamplifier ($5999 USD), BHK Signature Stereo 250 power amplifier ($7499), and BHK Signature Mono 300 power amplifiers ($14,998/pair). The voicing of the BHK Signature models was together done by King, McGowan, and Nudell, who collectively have more than 150 years’ experience in the audio industry. PSA sent me both a BHK Signature preamp (my subject here) and a pair of BHK Signature Mono 300s (for a future review).
The BHK Signature preamplifier arrived here from PS Audio’s home in Boulder, Colorado, in unorthodox packaging. The preamp, which weighs 22 pounds and measures 17”W x 4”H x 14”D, came tightly sandwiched between thick sheets of clear, semiflexible plastic attached to a substantial cardboard surround. The packaging acts as a suspension for the preamp during shipping. Neat.
The BHK preamp and amps are available in silver or my review sample’s black. Both come with a wooden top panel in gloss piano black, bonded to a panel of sheet metal to block electromagnetic radiation, this metal panel in turn attached to the rest of the case. Inset in the rear half of the top panel is a black, slotted plate that can be easily removed to access the tubes. Inside, below the vents, is a red LED that goes dark to indicate when it’s safe to remove the tubes. The chromed screws holding the access panel in place are the only brightwork visible.
The BHK’s glossy top nicely contrasts with the powder finish of its 1/2”-thick side panels. The front and sides are slightly beveled at top and bottom, with a horizontal groove machined into them about a third of the way from the top. These panels are connected with smoothly rounded corners. An accent strip runs across the top of the rear panel, continuing the styling around all four sides. The build quality of my review sample was rock-solid, with only a single, small misalignment on the rear panel; otherwise, the unit was fabulous to the touch.
The PS Audio logo at the top left of the front panel doubles as a standby/on switch. After the BHK Signature has been turned on, and any changes have been made to its balance and/or other settings, its small OLED display reverts to a numerical indication of the volume level that I found easy to read from across the room. The only other things on the BHK’s faceplate are a 1/4” headphone jack, a small button for cycling through the displays and entering information, and a good-size volume knob.
The rear panel is about as simple as a preamp’s rear panel can be: On the left are a tight grouping of power switch, IEC mains input, replaceable fuse, and two trigger outputs. Spread out across the remaining real estate are one pair of outputs and five inputs. Each input and the output has balanced XLR and single-ended RCA connectors, for maximum hookup flexibility. Each input can be custom-named using the display menus, and each can be configured as a home-theater bypass.
The BHK Signature has a solid-state output stage, and an input stage that includes two Psvane 12AU7 TII tubes. The circuitry is built up on dual-layer fiberglass boards with through-hole parts installation, all by hand. The fully balanced circuit achieves the industry-standard frequency response of 20Hz-20kHz, ±0.1dB. Only N-channel MOSFETs are used in the output stages of the complementary symmetrical topology, which, per PS Audio, results in lower distortion than can be provided by a mix of P- and N-channel components. The BHK Signature’s claimed total harmonic distortion plus noise (THD+N) at full scale (1kHz) is less than 0.03%. A power consumption of 60W is specified, with all power needs met by fully regulated, discrete MOSFET voltage regulators that draw from a single, oversize toroidal transformer. During my time with it, the BHK never ran hotter than mildly warm to the touch.
For this review, my sources were iTunes and Tidal, streamed from my iMac via a Nordost Blue Heaven USB cable to a Benchmark Media Systems DAC2 HGC digital-to-analog converter and headphone amplifier. PS Audio recommends balanced connection, advice I followed for all connections. The Benchmark passed along analog signals to the BHK Signature preamp and from there to the pair of BHK Signature 300 monoblocks via Dynamique Audio Shadow interconnects. Transparent Audio MusicWave Ultra speaker cables delivered signals from the amps to my KEF R900 speakers. For headphone listening, I used my NAD Viso HP50s and a 1/8”-to-1/4” adapter. Everything else in the system was the same as when I reviewed the Simaudio Moon Neo 350P preamplifier in March 2016. I still had the Simaudio on hand, and compared its sound with the BHK Signature’s (see below).
The sound of the BHK Signature was incredibly smooth. Everything I played through it had a palpable presence that washed over me like a slowly moving stream -- no pressure, no haste, no fatigue, just music. Voices emanated tangibly from the soundstage, easy to pinpoint in space. Kat Edmonson’s vocal in “What Else Can I Do,” from her Way Down Low (16-bit/44.1kHz, OKeh/Masterworks/Tidal), was lush and full of nuance. She sounded pained yet brightly optimistic. Her sibilants seemed true to the original recording’s intent. The supporting band was also vividly present. The double bass supporting the melody was deep, superbly firm, and effortlessly filled its space without any sensation of twang or overplucked notes. The piano was beautifully rendered, clear and present, with a realistic fullness of sound: left-hand notes never sounded bloated, right-hand notes never sounded sharp. The flute, violin, guitar, and supporting vocal snuck up on me gracefully, beautifully layered -- each appeared in the mix as a fully fleshed-out instrument or voice. This recording, through a less-able preamplifier, would have had a notably flatter presentation. Instead, the BHK reproduced from this digital recording a remarkably smooth, “analog” feel. In all respects, singer and band were more “here” through the BHK Signature than I’d ever heard them before.
On a Tidal playlist of world music I found “Gislene,” performed by the 12-member Haitian band Tabou Combo, from the compilation Tanbou Toujou Lou: Meringue, Kompa Kreyol, Vodou Jazz & Electric Folklore from Haiti 1960-1981 (16/44.1 FLAC, Ostinato/Tidal). “Gislene” has a Caribbean sound, with a frenetic beat and a wildly complex arrangement that showed just how articulately the BHK Signature could reproduce the music I fed it. Melodic, twangy electric guitar and a delightfully nasal voice (singing in, I guess, French or Haitian Creole) is accompanied by a busy mix of conga, tambourine, snare, cymbal, various hand and struck drums and assorted other percussion, and accordion. Through the BHK Signature, the male vocal was as fleshed out as Kat Edmonson’s, and intoxicating in its unusual (to my American ears) inflections -- the music’s remarkably complex style is a high-energy version of the Haitian Compas dance beat. Amazingly, it was quite easy to pick out single percussion instruments from the fray. Despite the wildness and complexity of the music, the BHK reproduced all of the higher-pitched percussion clearly against the very smooth vocal. This was not the hyper-vivid, “etched” articulation I’ve heard from highly resolving solid-state preamps; more important, through the BHK, the clarity of each instrument was musically compelling. That’s something that’s very hard to put my finger on; I’ll just say that the music sounded so natural and so right that I was drawn into it more than I usually am.
The soundstages presented by the BHK Signature may have been the largest I’ve heard from any preamp. It was able to present a Phil Spector-esque “wall of sound” without all of Spector’s postproduction wizardry. Electronic music frequently makes clear the boundaries of the available soundstage space, with sounds commonly moving about, giving the illusion of depth, or just appearing in unusual places. I put on the large and forceful “Magellan,” from Mike Oldfield’s The Songs of Distant Earth (16/44.1 AIFF, Reprise), and was astounded by the immense soundstage. The main melody is played on bagpipes, which were solidly anchored to my speakers’ positions -- but the supporting piano, percussion, and deluge of electronic sounds seemed to come from almost everywhere in the room, except for directly behind me -- a real wraparound effect. There was also a notable illusion of height -- some sounds seemed to come from a couple of feet above the speakers. The BHK Signature presented a remarkable illusion of space.
My earlier remarks about the BHK Signature’s smoothness and clarity also apply to Oldfield’s “Magellan.” Electronic transients never sounded harsh through the PS Audio, but were still clearly rendered -- its sound was smooth, without smoothing over transients in an unnatural way. The music had real presence, seeming to occupy a three-dimensional space, instead of being a flat plane of sound without body or substance. Through the BHK, even electronica had a spirited, enlivened feeling. Anyone familiar with electronic music will understand what I’m trying to say here: the BHK was articulate with electronica. Then there was the bass -- or rather, THE BASS. My KEF R900 speakers have never produced such strong, controlled, subterranean bass as they did when fed signals by the PSA. Bass lovers looking for a preamp should order a BHK Signature now.
Shifting from raw electronic power to something much more delicate and detailed, I keyed up the Overture of J.S. Bach’s Orchestral Suite No.2, performed by the Academy of Ancient Music under the direction of Christopher Hogwood (16/44.1 AIFF, London). Although the BHK Signature’s absolute resolution was very good, it was not superior -- I couldn’t hear more through the BHK Signature than I do through other preamps. With this recording, the BHK’s subtle warmth made itself evident in the solo flute’s higher octaves and the higher-pitched violin sections -- attacks were slightly rolled off or smoothed on just those notes where I would expect a bit more hardness or detail. In both cases, there was an absence of the shrillness that these instruments can actually produce, and that are audible through more highly resolving gear. Nor did the harpsichord have quite the hyperdetailed feel of plucked notes that I’ve heard from some all-solid-state high-end preamplifiers. That said, the violins, violas, and cellos sounded wonderfully sweet and delicate, and the music had a beautifully engaging presence. Overall, I found that the BHK Signature erred on the side of musicality and presence rather than leaning toward high precision and clinical neutrality.
Simaudio’s Moon Neo 350P preamplifier is a rock-solid performer overall, with good build quality for the price ($3700), attractive styling, and neutral sound. Reinstating it in my system after living with the BHK Signature for several weeks was enlightening. I prefer the look of the Simaudio to the black-on-black styling of the PS Audio, but when it comes to build quality, the story is different. The BHK Signature feels more solid and sturdily assembled than the Neo 350P, which feels flimsy in comparison. The BHK’s front-panel buttons and volume control had a feel of greater precision than their counterparts on the Neo 350P. The Simaudio’s eight-segment red LED indicators look dated next to the BHK’s more informative and modern OLED screen. The PS Audio costs $2299 more than the Simaudio, and feels like it.
The enormous soundstages I’d grown accustomed to with the BHK Signature shrank back to “normal” size with the Neo 350P. The Simaudio also removed much of the depth and three-dimensionality that I’d enjoyed with the BHK. The leaner-sounding Simaudio never quite exhibited the PSA’s bass slam, which sounded weightier down low. Mike Oldfield’s “Magellan” was smaller and flatter from front to back, and less hard-hitting in the bass. With Tabou Combo’s “Gislene,” the BHK Signature reproduced all of the many different percussion lines with a remarkable degree of separation that the Neo 350P couldn’t match. But while the PS Audio preamplifier’s sound was bigger, smoother, and clearer than the Simaudio’s, it couldn’t top the Neo 350P’s neutrality and utter lack of tonal coloration. That said, when the 350P was in the system, I dearly missed how the BHK could present music with almost tangible three-dimensionality.
Compared to its line-level outputs, whose sound had plenty of presence though never too much, the BHK’s headphone circuit had a more traditionally tubey sound, with much “fatter” midrange and bass. Comparing the built-in headphone amps of the two preamps through my NAD Viso HP50 headphones, I again found that the Simaudio was more clinical and neutral: the bass in Kat Edmonson’s “What Else Can I Do” tightened up and lost most of the tubey pudginess that I’d heard through the BHK, while in “Gislene,” the percussion cleared up to the extent that I was able to more easily track individual instruments on the soundstage. Most notably, the electronic sounds and bagpipes in Oldfield’s “Magellan” were crisper through the Simaudio than through the PS Audio. As with its line-level outputs, the BHK Signature’s soundstage was broader and more encompassing. The preamps’ headphone amplifiers clearly showed the effect that tubes can have in a circuit: the BHK had a stereotypically smooth, warm, tubey sound; the all-solid-state Neo 350P excelled at precision and strict neutrality.
In the BHK Signature preamplifier, Bascom H. King has designed, and PS Audio has built, an outstanding performer. It possesses the top-quality fit and finish that one would expect to get for $5999. Its sound was beautiful and alive, re-creating three-dimensional soundstages that were the largest I’ve heard in my room. Its excellent clarity of sound let me easily decipher even the most complex music, its bass was superbly firm, deep, and controlled, and its treble extension was clear and articulate. Through its preamp outputs, the tubes didn’t give the BHK the conventional, warm midrange sound of tubes -- though it did through the headphone output -- but I suspect that the tube(s) did give the sound more presence, which I think really helps it come alive.
PS Audio’s BHK Signature preamplifier is a statement product that produced beautiful music. I highly recommend that anyone willing to spend $6000 on a preamp arrange to hear one. I absolutely loved what I heard.
. . . Erich Wetzel
PS Audio BHK Signature Preamplifier
Price: $5999 USD.
Warranty: Three years parts and labor.
4826 Sterling Drive
Boulder, CO 80301
Phone: (720) 406-8946