Jun 27

Jun 27 PS Audio BHK Signature Preamplifier

There are times when the sound quality of one’s audio system exhibits significant improvement due to an upgrade of a component and no one would question why. Main examples are the upgrade of speakers, amps, or digital-to-analogue converters (DACs)—all of which I have gone through over the years. But is a significant improvement in sound quality possible due to the addition of a standalone preamplifier when such a component was not even part of your system before? In other words can a ‘middleman’ be allowed to interfere with your musical romance and help seal the deal? Well, as we shall see, the answer is yes: the middleman is the new PS Audio BHK Signature Preamplifier, at $6K retail, the subject of this review.

This is its first review. A very special thanks to Bill Leebens/PS Audio for making this review possible.

For several years now, I have been using a DAC that has a built in volume control, and hence allows a ‘direct to amps’ connection: the PS Audio DirectStream DAC (DS). Very pleased with the clean, transparent and natural sound, even my turntable connects to the DS via a phono stage (PS Audio NuWave Phono Converter) that converts on the fly to digital, and thus it too has no need for a separate preamplifier. The DAC does it all and does it beautifully, taking on responsibilities that never cease to amaze me.

As a reviewer, however, the practical necessity of allowing for many inputs so as to compare several sources of various kinds has become an issue. So, I have occasionally experimented by inserting a preamplifier in my system. Almost always, I found that it mucked up the sound. The bass would become muffled, bloated or fluffy, or the high-end frequencies would become edgy—or both. Perhaps a nice warm, sweet and silky sound emerged in some cases, but at the expense of covering up inner detail and natural timbre.

On the rare occasion when I found a preamplifier that came very close to or just about equal to the sound quality of the DS DAC’s own internal volume control, other annoyances prevailed: not enough inputs, or only RCA inputs, no sleep mode, or no front panel control even for volume (only remote control), or all vacuum tube based both input and output (not my cup of tea for practical reasons), and often priced way too high for what it offered my system let alone what I could afford. In short, I got into the habit of not trusting or wanting to use preamplifiers in my system.

The addition of the PS Audio BHK Signature into my system, however, changed all this. Not only did it significantly best the sound of the DS volume control, it suffered none of the annoyances just mentioned. This was a very unexpected and a welcome surprise to me. Add to that (icing on the cake) some other features that confirmed its uniqueness: it has a very fine and convenient built-in headphone amp, and an all encompassing remote control of the first water. When I summarized my reactions to my friend Mike Levy, CEO and Founder of Alta Audio Speakers and then went over with him the design and implementation of this preamplifier, he commented, ‘The design is ingenious’.

Some background: ‘There is no preamp like no preamp’

PS Audio has a history of being against the inclusion of external preamplifiers in a system, with its classic, ‘There is no preamp like no preamp’ motto. In fact, in one of his posts from August 12, 2012, titled ‘The era of the preamp is over’, CEO Paul McGowan made the following statement: ‘We’re all interested in music and its reproduction and the preamplifier has been central to most of us for most of the music we enjoy. The day of the preamp is over and I want to explain how we got to where we are and why.’ Fortunately, unlike most of us, when McGowan learns something with his ears that contradicts what he previously thought was true, he admits it, he then tinkers and he acts.

In some recent email exchanges with McGowan, he told me about his transformation as follows: ‘When I wrote that article the facts were correct, I had never heard a preamp that bettered no preamp. It wasn’t until I spent time at Arnie Nudell’s [Founder Infinity Systems, Genesis] house my opinion changed. I told him my story and he laughed and suggested I simply hadn’t heard the right preamp and promptly put my conclusion to the test. Arnie had the Aesthetix Calypso preamplifier [all vacuum tube, front and back end] as well as the DirectStream DAC. It was a simple test and the results were conclusive. With THAT preamp in the system, the music came alive in a way I hadn’t expected nor had ever heard.’ McGowan went on to use one in his own system. He ended his email to me with, ‘I would change my August 12, 2012 statement to read more like this: “Most preamplifiers do more damage to a great DAC and should be avoided when possible”.’

Meanwhile, legendary and passionate designer Bascom H. King (BHK) (Infinity, Marantz, Constellation Audio and Audeze, too) had been tinkering/listening to and helping design amplifiers and preamplifiers for many years, and came to the conclusion that, as he told me in a recent email, ‘an active system preamplifier, especially a real good tube unit, did something that made things sound better.’ Then more recently, he too was introduced to the Aesthetix Calypso preamplifier by Arnie Nudell, and as he told me, ‘Well, the Calypso handily trounced my solid state unit’. So he too acquired one for his system.

Around this time, McGowan commissioned BHK to design power amplifiers for PS Audio, culminating with the new highly praised PS Audio BHK Signature Amplifiers–endowed with a tube front end.

The amp collaboration led to the preamplifier as their next project. McGowan wanted a newly designed preamplifier that would best the Calypso. When I asked BHK how did the preamp project come to be, he told me, ‘I believe the preamp had it’s genesis at a lunch meeting at Arnie’s house and we laid out what would be the topology of the design. Well, I went off and started the design and working with the very talented Bob Stadtherr, Chief Engineer of PS. We worked out the schematic and many other details that ended up with a first physical prototype. I got that and worked out some bugs with it and put it in my system. Holy God Almighty! It sounded incredible and handily beat my Calypso preamp.’

That is how the PS Audio BHK Signature Preamplifier came to be. Lucky we are.

A quick list of some key features and specifications

Here I list some of the specs, but also add in some personal comments that further explain and elaborate. For a full listing of specifications and more, go here.

100% analog signal path. Weight, Dimensions, Color: 22 lbs, 14” x 17” x 4”, Silver or Black. (I reviewed a black one.)

5 inputs (stereo pairs), with each having both XLR and RCA (you choose which to use); both are fully balanced. Labeled 1-5, they can be named, and each can be assigned Home Theater (HT) Bypass.

2 output pairs, one XLR, one RCA.

Input and output stages: Two 12AU7 dual triode vacuum tubes in the input stage; zero- loss. (One can swap the tubes for others if you want to roll with different ones.) Output stage is a high-bias class A MOSFET design. All inputs are converted to a pure balanced signal by the dual triode vacuum tube. (Fully balanced input to output.)

Volume Control: stepped discrete input attenuator is combined with a switched gain adjustment controlling the gain of the vacuum tube. (0.5 dB steps.)

Output level/impedance: 4.0 Vrms/less than 100 Ohms.

Bandwidth: -3dB 0.1Hz - 200kHz

Power supply: internal oversized toroidal analog power supply feeding 5 MOSFET based discrete regulators.

Headphone amplifier (built in, discrete MOSFET) with a 1/4” output on front panel of unit.

Standby Mode, which has the effect of turning off the vacuum tubes to preserve their life span, while keeping on the solid state circuitry. (PS logo button (blue light) located on the upper left of the front panel of the unit.) It also controls two +12 volt trigger output ports that can be used to turn on/off compatible amplifiers at the same time as the preamp when using the Standby Mode button.

Front panel manual control: Volume, balance, input selection and naming, HT bypass assignment.

Infra red remote control: Not only does it control the basic functions of the preamp, it also controls other PS Audio equipment in your system such as a DS DAC. For example, you can control the volume of both the preamp and the DAC, and you can switch among the DAC’s modes (USB, I2S, Bridge, etc.). Fantastic. Another nice feature is that when you first push a button, the remote lights up so you can see all its functions (good for night time), then goes off after some seconds. There also seems to be items on it that relate to some future components/use. It is a very nicely thought out remote. During my review, I put the DAC’s own remote out of service.

Setting up and using the PS Audio BHK Signature Preamplifier

The unit is elegant looking, discreet, quiet and simple. At a glance, on the outside it looks similar to the PS DirectStream Junior DAC; it even has the same length and width except it is thicker (4” versus 2.75”). On the front there is just a knob (for volume control, etc.), a small button, a monitor for displaying the volume level (0–100), the headphone output, and the Standby Mode button in the upper left corner. In addition to the 5 inputs and 2 outputs on the back, there is a power switch (highly recommended to always keep on), an AC input, the 2 trigger outputs, and 1 fuse. The top has the same beautiful piano black cover as does the DS DAC, except now it has a grille and one can see through it an attractive dark red glow of light inside (back left) when the unit is powered on (even when the two small orange glowing vacuum tubes are off via Standby Mode). It is highly recommended that you use a high-end power cord, I did so; after all, this is a $6K unit, don’t go cheap on the power cord! I set it on its own shelf within my vertical Salamander Designs audio cabinet to isolate it; but, as with many PS Audio products, you can stack it if you wish by taking off the footers.

When you have all your inputs/outputs connected, and the power is on (in the back), it is time to press the Standby Mode button to turn the tubes on. The unit comes with a pre-set amount of warm up time (mine came with 45 seconds, I left it at that) that is displayed on the monitor moving backwards second by second. This amount of time can be changed; its main purpose is for using the trigger outputs (I did not), the idea being to allow the unit to warm up before shooting out the 12 volts into your amps to turn them on (if they are endowed with such trigger inputs).

I attached my DS DAC to input 1 (XLR) and my phono stage (attached already to a turntable) to input 2 (XLR). I did not experiment much with naming these inputs, particularly since as a reviewer I would be attaching all sorts of things over time; but I would expect to always keep the DAC in input 1, so I tried naming it DSDAC. I failed; I ended up inadvertently setting the input 1 to Home Theater (HT) and messing up the volume. I figured out how to get it back to normal at which point I decided not to fiddle around with this feature anymore for now. (These types of nuances are firmware related, and unlike the DS DAC, upgrades in firmware have no effect on sound quality. In fact, the newest firmware contains the ability to see how much time in use your vacuum tubes have amassed.) I also kept the phono stage (PS Audio NuWave Phono Converter) attached to the DAC via I2S, so that I could compare that digital path (input 1) for vinyl with the purely analog path (input 2).

Thus I had the luxury–at the push of a button on the remote-by toggling between input 1 versus input 2 while listening to vinyl to compare it played in the two ways just mentioned. Keep in mind that before I had the preamp installed, I could only listen to vinyl as a pure digital path (phono stage conversion to digital sent to DAC sent to amps).

I found that only a minimal amount of burn-in time for the unit was needed; only the headphone amp required ample time. Even within hours a noticeable change in quality was evident; and it all blossomed over the next days. And the cool thing is that the unit itself continues to burn in even when in Standby Mode (hence no playing music is required; tubes are off). The headphone amp, however, needs music playing. I made a habit (over a 2 week interval of time) of always putting the unit in Standby Mode before going to bed; except every couple of days keeping all on over night with headphones playing music in repeat mode. Suffice to say this did the trick.

Important note: while changing volume, some tiny clicking sounds can be heard at various specific levels as you change (particularly noticeable when using headphones); this is normal as confirmed by PS Audio and is a property of the unit’s volume control.

Sound Quality

In this part of the review I am primarily comparing here the PS Audio DS DAC using its own internal volume control versus inserting the PS Audio BHK Signature Preamplifier between the DS and my amps (Merrill Audio Veritas mono blocks). The DAC was equipped with a Bridge II and the newest firmware upgrade (‘Torreys’ as of this writing). For music player I used my Mac mini (upgraded by Mojo Audio with a separate power supply) utilizing both JRiver MediaCenter 20.0.132, and Roon 1.2, and using both ethernet (as a crossover cable) and USB at my leisure for sending the files from Mac mini to DAC (e.g., Bridge or USB mode). For vinyl, I was comparing three different scenarios as described at the end of the previous section: one using no preamp (purely digital), versus two using the preamp (one partially digital, one purely analog).

With use of the BHK: In addition to exposing a lovely increase of resonance, air, reverb, spacial definition and openness galore, joined with more instrumental density, weight and superb bass, voices in particular became layered with complex, gorgeous textures. Luscious.

Prime examples for male voice include Nat King Cole, ‘Love is the Thing’ (CD rip), Belafonte at Carnegie Hall (24/96) and Elvis Presley’s version of ‘Fever’ (24/96), from the album The Essential Elvis Presley. I also add in Julio Iglesias only because I must admit that my wife at first thought I was crazy when she first noticed this new device (preamp) in my audio cabinet—until I put on one of her favorites by Julio (from the album My Life: The Greatest Hits (CD rip)): ‘Crazy’, as well as his version of ‘Vincent’ (sometimes known as ‘Starry Starry Night’) about Vincent van Gogh, originally written/performed by Don McLean in 1971. She was stunned by the detailed, rich, full sweet sound and the natural textures of his voice and venue–and so was I. She helped me dust off and clean the cabinet! So intrigued was I by the sound quality that I let the entire album play.

No less for female voices. For example, I have never been a fan of blue grass music; but, my gosh, check out the 2000 album (CD rip) ‘Rising’ by Misty River, an all-female bluegrass quartet (including a mother and daughter) involving acoustic guitar, banjo, bass, fiddle, accordion, and more; but above all, absolutely lovely harmonizing vocals. And back to Vincent van Gogh, I suggest the track, ‘Paper Van Gogh’, from Shelby Lynne’s newest album, I Can’t Imagine (24/96). On the BHK, these voices (and all else) sounded heavenly.

Speaking of heaven in a very different way: Oh man, what can I say, David Bowie’s last album (2016), the jazz-influenced Black Star (24/96) released right after his recent death, the track ‘Lazarus’. It left me in such a state after listening to it on the BHK; so spacious, eerie and visceral, and with heart-wrenching lyrics—I reached for the whisky bottle, what else could I do?

For Jazz: Want some deep articulate bass and liveliness in spades? Check out on the BHK the classic ‘You Look Good To Me’, from (CD rip) We Get Requests by the Oscar Peterson Trio.

In addition, never before has my system displayed that triangle (left channel) nor the piano in such a lively manner. Want amazing cymbals? (always my favorite sources of testing): Live album Trilogy by the Chick Corea Trio, Track 16 ‘Piano Sonata: The Moon’. Brian Blade’s complex and delicate cymbal work alone is so full of life and is mesmerizing on the BHK; start listening at about 10 minutes into the track.

Classical? What better than the glorious sound and repertoire of the cello. ‘The (Bach) Cello Suites According to Anna Magdalena’, performed by Matt Haimovitz using a Baroque cello (has no endpin). (2015, PENTATONE Oxingale Series, SACD). The sustained sound of reflections, breathing, together with the mind-boggling natural timbre of the cello as displayed by the BHK just knocked me over. I had always dreamed of acquiring a cello for my apartment (as like a fine piece of furniture) such as the one used by Zuill Bailey, a Matteo Gofriller 1693.

But after listening to the above album by Haimovitz and also learning that Bailey performed once in an HBO series ‘Oz’ in which he played a cellist-murderer who harpooned someone with the endpin, I have decided to play it safe: If I ever do get a cello, it will be of the Baroque kind! And finally, I must mention Brentano String Quartet Plays Beethoven Late String Quartet Op. 130, that I recently reviewed.

I’ll have to get my violist friend Daniel to come by and hear it now on the BHK; even more stellar sounding.

Without going into details, suffice to say that playing vinyl yielded similar results as the digital file examples above. Inserting the preamp significantly bested not using it, and I would rank the pure analog as having the upper hand over using the DS DAC in between, but it was close! Suffice to say, I am now heading towards upgrading my turntable cartridge so as to even better gain the advantages of this remarkable preamp.

Headphone amp

The first-rate built-in headphone (HP) amp it quite cleverly designed within the preamp to take as much advantage as possible of the preamp’s already unique design and quality. It is driven from the main outputs of the preamp, i.e. from the output MOSFET buffers, bypassing being directly driven by the input stage vacuum tubes (which would have been extremely complicated to accomplish). As BHK told me upon inquiry, ‘we use a coupling transformer from the main outputs of the preamp to the HP amp input to gain the use of both output phases for signal summing, gain increase, and noise cancelling. So, the full signal path is used of the preamp to drive the HP amp.’

I used two closed models for my testing: my personal Master & Dynamic MH40 (reviewed here), which are my standard overall reference, as well as the very high level Audeze LCD-XC (special thanks to Wes Bender from Wes Bender Studio in NYC for loaning me these incredible Audeze cans). I have used/heard these two models on many standalone headphone amps over the years.

I was very satisfied with the sound quality; transparent, full and open with ample bass, sweet midrange and detailed highs. The ability to simply snap in cans to the preamp while the music is playing on my system is something I have longed for (haven’t you?). When you do that, your system speakers stop, and only the cans are on playing whatever had been playing. Pull out the jack, and the speakers are back on. I now will never even think about acquiring a separate standalone headphone amp. Remember that there are standalone headphone amps on the market that can cost even as much if not more than this entire preamp unit and are completely devoted to headphone usage; so if your objective is to have the very finest standalone headphone based system, you can look elsewhere (perhaps check out the new ‘The King’ Audeze headphone amp designed by BHK that retails for $4K?). But if, like me, your main joy is listening to music through a fine speaker-based system, and you want an outstanding headphone amp thrown in the deal for good measure, then look no further.

Summary

What the PS Audio BHK Signature Preamplifier brings to the table is a significant achievement. For me, it seals the deal, and I believe it will satisfy audiophiles on both sides of the aisle (digital versus analog, tubes versus solid state), and those in between. Taking into consideration its price, simplicity of use, extraordinary quality of sound, design and features such as an included internal headphone amp, I must honestly say, ‘There is no preamp like this preamp’. Very highly recommended.