HifiZine
The enthusiast's audio webzine

PS Audio BHK Signature 300 Mono Amplifiers

If you have followed the audiophile press over the last couple of years, you have no doubt read a fair bit about PS Audio and their new product releases. While most of the attention has been on their award-winning digital players and DACs, the company that seemingly never sleeps has also launched a new line of power amplifiers, bringing back a product category PS Audio had not been actively manufacturing for some time. While chief Paul McGowan had provided hints about the emergence of these amps on the PS Audio online owners’ forum, the final product surprised more than a few people: the company known for its cutting edge digital and Gain Cell designs decided to incorporate a tube circuit in the new high power amps. Wasn’t this the same man who once said he’d never have a tube in any of his products?

The story of how PS Audio’s BHK series of amplifier came into being is now well-documented elsewhere (see a video history of the design at http://www.psaudio.com/bhk-signature-300-amplifier/). In short, after boldly stating his intention of creating one of the best sounding amps in the world, Paul McGowan was not satisfied with the sonic results he was obtaining from his initial designs so he brought in outside help in the form of legendary audio designer Bascom King. This pair, together with Arnie Nudell, set to work to really deliver on the stated goal of building a truly world-class power amp. Yep, I know, most companies claim to offer world-beating products, but when you learn that Bascom King required complete control over the design and eventually convinced the digital diehards at PS Audio that only a tube would do, you have to believe something special was in the works.

The end result is a large, weighty hybrid amp with a unique circuit design that employs a tube input stage coupled to a high-bias balanced MOSFET output stage. A pair of self-biasing Golden Lion 6922 tubes run in each BHK 300 monoblock (there is also a stereo version available). Since replacement tubes of this type are easily found, this offers owners a form of tailorability if inclined to experiment. Tube life is estimated at between 12-24 months of regular use, which entails the owner turning the input stage off between listening sessions by means of the front panel switch, leaving on the rear main power switch to keep the output stage ready to go. As a guy who leaves his gear on all the time, I had to learn this little habit from scratch.

I was on hand for the debut of these amps at RMAF a couple of years back, but as I recall, a problem there prevented me forming an impression of anything on the day. I was intrigued by the seriousness of the effort so I kept an eye on the emergence of these amps. As I picked up early reports of what these amps could do from other listeners, I really wanted to hear them properly for myself. Thanks to Bill Leebens at PS Audio, the opportunity finally arrived and I’ve had these in my reference system since April, shortly after shipping back the thoroughly lovely Valvet monoblocks I reviewed earlier this year.

The BHK 300s are heavier than most other amps I’ve handled, though physically they are not the biggest, with the chassis being only 14” deep. Each mono is over 80 pounds and you feel every bit of that weight as you manhandle these into place. The poor delivery guy puffed as he waited for my signature, and the boxes showed signs that more than a few people had struggled to handle these safely en route to chez moi. That said, with a little effort and some sliding of boxes across the carpet, I had these unpacked and ready to connect up within minutes, giving them the suggested 24 hours of on-time to prepare for listening.

Let the music flow

If you asked a handful of audiophiles which components make the most difference in a system, I suspect the majority would pick the speakers, then maybe the front end components, with amps occupying the space above cables and cords as determinants of sound quality. With all due respect to the ‘garbage in-garbage out’ brigade, I accept this hierarchy of performance although I do recognize that everything in the chain has some effect on what you hear.

I mention this as it’s interesting to determine just what an amplifier does that impacts the sonics. As the differences between tube and solid state amps seem to have narrowed, there is a plausible argument to be made that any well designed amplifier should just increase the signal and add little else. That’s all good in theory, but in practice, many people report hearing differences between amps, and these differences seem meaningful enough for some to spend a whole lot of money on one box rather than another.

In my experience, amplification does matter, and some amps just sound better than others – in my room with my gear. Sure, I can run my Von Schweikerts satisfactorily loud with an old Naim Nait integrated or with a 20W Raven tube amp, and in both cases I can appreciate the sound I am hearing. But again, in my room, with my gear, the beefy BAT VK 500 sounds quite different than those lower powered models, and all of these sound darker than a pair of Spectron monoblocks. So when I connected the BHK 300 monos, I was expecting I’d hear something different… but it took almost no time for me to appreciate that no matter what amps I’d heard before, there was something quite distinctly different happening here.

While I am loath to ever state that anything is the best I’ve heard, I am going to break that tradition here. The BHK Signature 300 Monos really are the best amps I have ever had in my home system. There, I said it. They are not just better sounding than every good amp I’ve heard in my own room, playing my music, but they have shown up my long-lived references, the Bybee-enabled Spectron Musician III Mk2 SE monos that have seen off all other challengers for years (a list that includes some I’ve owned such as the BAT VK500, and others I’ve had the joy to review, such as the DAC Cherry Jr and Nuforce 8). I’m not in love with the looks of the BHK 300s, I hate the weight, and it annoys me that I have to remember to turn them off else risk burning out those input stage tubes too soon, but I’ll tolerate all that to listen to them dig out more musical reproduction from disks I’ve heard hundreds of times. You can leave now if you just wanted my conclusion.

Here comes the music

First impressions are that these amps sound big. The music just flows out and fills the room. It extends a soundstage beyond the speakers in both depth and width. And, despite the presence of tubes, these amps do not in any way sound warm, in the classic tube sense, but come across as solid bodied and resolving at the same time. Coupled with the size is a degree of precision that is a little startling when you hear it. Instrument placement is clearly delineated, not just in giving solid phantom images but even two instruments leaning toward the same channel can be separated cleanly in the soundstage. How much of this is an artifact of the recording is not the issue – the amps are able to delineate instruments that other amps seem to blend more closely, and they do it by making the whole presentation life-sized.

Over several months I made copious notes, exhaustively registering what I was hearing in a long list of track names and musical details. Let me give you a small sample. Take a dated chestnut we’ve all heard a million times, like Floyd’s Dark Side of the Moon, and imagine what it might be like to experience it anew, with Gilmour’s guitar on Breathe now reproduced more as a live player, not just adding an overlaid riff or lick here or there. This iconic studio opus sounded like I’d stumbled on a new mix, yet nothing had changed but the amps. Floyd aficianados argue endlessly on forums over which version of this album is the best sounding, and I have a few copies of this recording myself. To my ears, the differences rendered by playing them through these amps dwarfed any sonic difference heard between the various releases. That is how much impact the BHK 300s have on my system.

Joan Armatrading’s LP Show Some Emotion is an album I use to set up cartridges as it enables me to hear small changes in arm height and alignment. Used with these amps, I heard Joan deliver vocal lines that propelled the lyric in a percussive delivery more physically real than I’d heard in 40 years of listening (yes, I’ve had that album that long). When this happens with old 1970s staples I know intimately, it tells me something very good is in the system.

I ran through a litany of tracks I use to calibrate my ears to a new component, and my notes show that this sense of hearing something different with these amps is consistent. Ronnie Earl’s Grateful Hearts album has been played on every rig I’ve used for the last 20 years and for every review I’ve written for the ‘Zine. I love the music, but I acknowledge that the bass can be be somewhat vague, lacking distinction on some tracks. Here, with the BHK 300s, it was articulated and present to a higher degree than I’d previously heard. On Patricia Barber’s Modern Cool, percussive details came across with a realism that was startling; Tord Gustavsen’s trio recordings presented more space between bass and piano; and on Bob Dylan’s Changing of the Guards from Street Legal, the rhythm section had a sense of swing where I used to hear only a shuffle. Change indeed.

What’s most impressive here is that few of these recordings are considered audiophile classics, but the BHK 300 monos brought a sense of realism to the reproduction that made every one of them sound better. Even mining old rock recordings from Queen such as Sheer Heart Attack or the Doobie Brothers’ Greatest Hits, I found myself remarking that music just sounded better. In fact, so surprised was I by this that I found myself dipping into music I’d not listened to carefully in years, across various genres, spending many enjoyable hours re-hearing the depths of my old collection. From Shostakovich on vinyl (the Borodin String Quartets on Melodiya) to Joe Pass on CD (My Song, on Telarc) I found myself smiling repeatedly at the joys still to be mined in my collection. Is there a better recommendation than this for a component?

It can prove difficult to isolate just what it is these amps do that improves on others. Yes, they offer very good, articulate bass, but they are not as warm or dark sounding as my old BAT VK500. They reveal the distinctive sounds of different cymbals, but so did my Spectron Musician IIIs. There’s a loveliness to the midrange that is almost as sweet as the Valvets I spent happy months with earlier this year. Taken together, this sounds as if the BHK 300s are an amalgamation of the best parts of other amps. That is true, to an extent, and one should not underestimate the value of such a combination of qualities, but even this does not tell the full story.

What I find myself thinking after several months with these amps is that there is a wholeness and ease to the reproduction of music that makes everything sound a little more real, a little more present, a little more spacious and a little more pleasing to hear (and to be honest, sometimes it is not just “a little” but a whole lot more). When you try to describe the difference between a live instrument sound and its recorded equivalent, you run into a similar challenge. The differences are easy to hear but less so to describe, and that’s the realm I find myself in here.

Many amps sound good but the BHK 300s just seem to sound bigger and better. It’s not just about frequency extension or resolution, attack or decay, the typical audiophile attributes we tend to listen for in auditions. These are surely important and give rise to the experience of music in physical space. But it’s actually something about the completeness of the instruments’ sound signatures, the one you hear in real life which makes it more palpable than any recorded version. It speaks to how a string’s vibration is launched and sympathetically enhanced by the wooden body of a cello; or to how a cymbal’s splash seems to hang slightly above the metal, suspended in the air for a moment before tailing off into space. There’s something whole about the live experience of music that is quintessentially different from the version launched at you by most stereo systems, and we hear this difference without even thinking about it. But sometimes a piece of gear seems to take you nearer, to be a little more complete, more lifelike in its presentation, to make you react a little more like you do to the real thing. The BHK 300 monos have that quality. Once experienced, it is very difficult to imagine being completely satisfied with less.

Yet there is something further these amps provide that captures attention. They have sufficient power to sound at ease even on complex music. Multi-instrumental recordings are untangled, allowing you to hear into the complex soundstage in a manner that I believe explains something of my re-experiencing of old familiars. Each instrument seems more fully delineated, allowing guitars and keyboards on rock music to occupy distinctive spaces, even as they interact and react to each other. I always felt that was one advantage of more powerful amps on my speakers but the BHK monos take this beyond simple resolution of details. Music seems to float freer from the confines of the cabinet, side to side and front to back, allowing you to follow individual lines with ease, layered and woven together into the sonic picture that emerges. All told, these amps give form to music in a manner that is most pleasing to this listener.

If there’s a caveat here, it comes from my somewhat brief experience of these amps with another speaker, the JWM Alyson, a pair of which I received some months into the BHK review. The Alysons will be subject to their own review shortly and they are a fine speaker. That said, I found the difference between the BHK 300s and other amps, such as my BAT VK500, less dramatic with these speakers than I did with the Von Schweikerts. I would not read too much into this as I still preferred the results with the BHK 300s, but it’s a reminder that the amp-speaker interaction is a partnership you should always audition for yourself.

Power and cables make a difference

In a rather direct pointer to the importance of power cords, the BHK monos ship with what they describe as ‘courtesy’ versions, basic ones that will allow you to plug them in but which PS Audio recommend you replace as soon as possible. In fact, my review pair did not even have these – no matter, I have more than a few cords lying around.

I started with the Thunderbolt cords developed but never brought to market by Spectron. They sounded very good, as they usually do with any amp I use them on. Over the course of time I changed to a pair of Pangea AC9s and was surprised to find that these affordable thickies produced a satisfying, warm sound that many people will find as easy on the ears as they are on the pocket. While I’ve had mixed experiences with Pangea power cords on other components, there’s no doubt they work well on the BHK monos.

From here I had to try a pair of old Virtual Dynamic Davids, a mid-level offering from the now defunct cable company (re-born now as High Fidelity cables). Still found used, the Virtual Dynamic cords are famous for an impossibly stiff construction which requires pre-bending to sit comfortably in most components. On the BHKs these sounded excellent in the midrange and above but could be a bit ‘lumpy’ in the bass on some recordings,

Wireworld were mentioned in several online forums as a good match and the company was kind enough to let me try a pair of their Platinum Electras with the BHK 300s. I’ll sum these up by saying it’s a good news, bad news situation. The good news is these sounded better than anything else I had to hand, even the usually great sounding Thunderbolts. The bad news is that these cost a lot of money ($1700 for a 1m cord). Worse, Wireworld believe strongly that they are optimized at 2m lengths, which is what they sent me, adding a further $1300 to each cord’s price.

I can’t speak to the length issue but I will say the Wireworld cords brought out that last bit of magic that made me prefer them over all others. Their particular contribution was to make instrumental lines just that little bit cleaner, the bass a little more articulate, the soundstage a tad wider. I know, a ‘tad’ of improvement might seem a poor return for a significant price hike over the Pangeas but in audiophilia, it’s those little extra qualities that really matter. If you have the money, or are considering these amps as your final purchase (and they are that good) then you might want to factor in the benefits of cords such as these.

Are other power cords likely to be as good? Everybody has their own preferences and favorites, and PS Audio have their own up-market cords which surely work well. But in my room, the Wireworld Platinum Electras are definitely a synergistic match with the BHK 300s. So much so that my interest in further comparison stopped there.

The amps accept both RCA and XLR interconnects, with the latter strongly recommended by PS Audio. I listened with High Fidelity RCAs and various PS Audio and Grover Huffman XLRs and found the differences meaningful. While I love the High Fidelity cables generally, the XLR connection seems to give everything just a little more life. As such, I concur with the manual’s recommendation to use the balanced connection if at all possible.

As for power conditioning, PS Audio naturally recommend a P10 conditioner just for the amps. Worse, they tell me that one P10 per mono is optimal. Yikes! I use a P5 for my front end and find it an important contributor to my rig’s sound. I never power my amps from it since I found it whitewashed the bass out of my Spectrons and anyway, PS Audio suggest the P5 would not quite cut it powering these monos. I do routinely use a two socket Audience Adept Response for my mono amps, and it has proved excellent with every amp I’ve tried. However, I am hard pushed to tell if it has any real benefits with the BHK 300s which seem to sound very similar plugged into it or not, particularly with the Wireworlds. What this tells you about the reaction of these amps to other conditioners, I can’t say, but it does suggest the PS Audio BHK 300s are able to deal with the vagaries of typical house wiring quite well.

As mentioned, given the use of two 6922 tubes per mono amp, there’s more than few options out there for those who like to roll. Tungsram 7DJ8/PCC88s are recommended by many, but I can’t comment on their sonic impact as I didn’t have any on hand.

Throughout the review I kept the amps on PS Audio Powerbases which are a great fit, unsurprisingly perhaps. They might even have improved the sonics but I did not feel too much like lifting these 80-pounders on and off for serious comparison. PS Audio suggest that supports do matter, and I am inclined to believe this is so, but at 80 pounds per amp, choose any footers or supports wisely.

Conclusion

When PS Audio decided to re-enter the amplifier market with a statement product, I am not sure even Paul McGowan anticipated what would result. That they have succeeded in creating something special is clear from my listening. The process of bringing on board a legendary designer and allowing him freedom to design to a sonic target while keeping costs in the realm of reasonable (ahem!) is more than mere advertising hype. At nearly $15k for a pair, these are not highly affordable products but they are superior to any amp I’ve heard in my room, or most other rooms for that matter. How many products can you say that about? Yep, these are the best I’ve heard, and by no small margin.

Manufacturer/product information

• Manufacturer’s web page: http://www.psaudio.com/products/bhk-signature-300-monoblock/
• Price (RRP): $14,998 per pair

Specifications

• Zero-loss parallel vacuum tube input stage
• Differentially coupled, paralleled, balanced MOSFET output stage
• RCA Single ended input
• XLR balanced input
• 300 watts 8Ω
• 600 watts 4Ω
• 1000 watts 2Ω
• 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
• 83 pounds

Associated Equipment

• Digital: PS Audio PWT/PWDII
• Analog: Artisan Fidelity Garrard 401, Ikeda 407 arm, Charisma 103 and Ikeda 9TT cartridges
• Preamplification: ARC Ref 2SE phono, SMcAudio VRE-1 preamp
• Speakers:Von Schweikert VR5 Anni II
• Cables: Spectron Thunderbolt and Absolute Fidelity power cords, Von Schweikert loudpseaker cables, PS Audio, Harmonic Technology, Purist Audio, and High Fidelity interconnects.