The Audio Beat - BorderPatrol P20 EXD EXS Stereo Amplifier

BorderPatrol • P20 EXD EXS Stereo Amplifier

by Roy Gregory | October 17, 2014

© www.theaudiobeat.com

The BorderPatrol P20 is no ordinary amplifier. In fact, there’s nothing ordinary about the company or the man behind it, one Gary Dews, late of Yorkshire and Brighton in the UK and now Maryland, USA. That’s an eclectic, contrasting, even contradictory path, an odyssey that has left its own indelible imprint on the very nature of his designs. If the audio world is constantly being divided and subdivided into ever more clearly defined pigeonholes (each with its own matching set of deeply held and just as deeply divisive prejudices), here is a product that defies categorization and confounds stereotypes. The amp uses 300B output tubes, but it isn’t single-ended (although there are BorderPatrol models that are). It’s a power amp, although it’s also available with a variable-gain input to create a single-channel integrated. The open chassis might look ultra-traditional, but in fact both the materials and the modular construction are anything but.

Even the product range is more difficult to understand than it looks at first glance, but only because you expect it to share the same logic as more conventional lines. However, once you get your head around the fundamental thinking here, it all starts to make considerable sense -- even the fact that the amps sound as different (and assumption busting) in musical terms as they are on paper. These aren’t just tube amps, they’re 300B tube amps -- yet they sound anything but "tubey." Their power ratings place them firmly in the low-powered category -- yet the BorderPatrol amps drive a quite astonishing range of speakers and do it with considerable authority. In fact, anybody who sat through the speaker setup seminars at RMAF last year will have heard the P21, something that tells its own story. Let’s face it -- if I’m selecting equipment for use in those seminars, I’m looking for a product that will deliver reliably and on cue, withstand the necessary abuse that constant system changes necessitates, and yet still ram home the musical point in no uncertain terms. Oh -- and I’ve got to want to listen to it for three days solid. Make no mistake, the inclusion of the P21 in that seminar system is a serious recommendation in itself. The full review comes more by way of explanation.

So, the place to start with the P20 is with the logic behind it and the rest of the BorderPatrol line, because as will quickly become apparent, they are inextricably linked. While much is made of the inherent linearity of triode amplifiers, that is, just as with any other amplifier topology, only part of the story. That linearity is a function of the extreme simplicity of both direct-heated triode tubes themselves and the circuits within which they’re used. But that simplicity is a double-edged sword. As transparent as it makes the amplifier to the signal, it also makes it transparent to operating parameters and system loading. Throw in the inherent inefficiency of triode output tubes and the low power ratings that result and you have a scenario in which the amp sounds as sweet as a nut -- just so long as it can drive the speaker it's hooked up to and meet the complex dynamic demands of the signal its receiving. Hence the frequent association of SET amplification with horn speakers and other ultra-efficient designs -- and the limited bandwidth that results. Remember those prejudices I referred to: now’s the time to trot out that old saw, "Triode amps -- nice mids, shame about the frequency extremes." Which is exactly where the BorderPatrol story starts. As a successful Audio Innovations dealer, the young Mr. Dews wondered to himself just why we had to put up with the limited choice of speakers and that soggy, rounded and disjointed bass response, just to enjoy the clearly audible magic of tube mids. Experience convinced him that the issue wasn’t so much the efficiency of the speakers but their load characteristics and the inability of the amplifier’s power supply to meet their demands -- something their very transparency made all too obvious.

The very first BorderPatrol product was a direct response to just that conclusion -- an add-on power supply originally aimed at the Audio Innovations Series 500 integrated and First and Second Audio power amps. Nearly as big as the amps it partnered with, and almost as heavy, it offered an independent high-voltage supply to the tubes. But this was no ordinary supply, instead featuring massive choke input regulation and tube rectification. Now, a lot of tube amps offer tube rectifiers and choke-smoothed power supplies, normally through capacitor-input configurations. Choke-input supplies are rare indeed, partly because they are big, heavy and expensive to build. But what they also do is deliver superior voltage regulation and noise rejection, resulting in quieter, stiffer power supplies -- just what the tube doctor ordered.

Hook up that original supply to the (ultralinear EL34) Audio innovations Series 500 or a First Audio and the sonic transformation was frankly astonishing. Turbo charging an engine will deliver twice the power, but in sonic and musical terms this was way, way more than that. It wasn’t really more power; it was great dollops of honest to goodness musical authority -- right across the musical bandwidth. Suddenly, rather than folding at the knees every time the going got tough, the amp responded promptly and enthusiastically irrespective of frequency. It didn’t deliver more power, it just delivered more of its rated power more of the time. Suddenly the top-end had air and poise, real energy and a stable acoustic, bass notes had leading edges and a shape -- and caught up with the rest of the music, starting (and stopping) on time. For anybody used to the polite, charming and inoffensive performance of the standard Audio Innovations units, the dynamic grip, musical substance, drive and sheer sense of purpose that exploded out of systems driven by the BorderPatroled versions came as a considerable shock.

Of course, the limited range of tubes used in audio circuits meant that you could easily use the BorderPatrol PSU on other designs too, so it wasn’t long before BorderPatrol supplies were cropping up connected to all manner of different amps. Fitting such a supply is a professional job, not a DIY task or a plug'n'play upgrade, but significant numbers of people were shipping their amps to BorderPatrol to have them modified -- to considerable musical effect. The rest, as they say, is history, but the existence of that first power supply serves to explain just how and why the BorderPatrol product line developed the way it did -- and why any BorderPatrol review needs to embrace not just one product, but the whole range of available options. Let’s take a look at the landscape.

BorderPatrol now offer three different power supplies, starting with the original version that can still be fitted to existing designs from other manufacturers (those using EL34, 6L6, 5881, EL84, 300B, Super 300B, 2A3 output tubes, as well as some that use the KT88/6550). Having worked out what made tube amps tick, Mr. Dews’ next logical step was to design the complete amplifier. Having control over the composition of the audio circuit (rather than having to produce a universal device) meant that the power supply could be further refined and the units that pair with BorderPatrol’s own amplifiers might look outwardly identical but are in fact significantly more complex and sophisticated than the original ones, with independent high-voltage supplies for the output tubes, input driver tubes and negative bias, along with filament supplies for both the output tubes and small-signal tubes. Latterly he has also added the larger and significantly more expensive EXS version reviewed here.

When it comes to the audio-chassis side of the range, the original SE300B design was a stereo amplifier that used a single pair of 300B output tubes to deliver 10Wpc, but it quickly spawned a whole family of options, all using the same basic bodywork and power supply(s). The S10 is also a single-ended 300B design, but uses two power supplies, one for each channel. The S20 adds a second pair of output tubes in parallel to the first, and uses two external power supplies. The P20/P21 is a push-pull 300B design with the same power-supply options (the '20 using dual supplies to the '21’s single external unit), while there’s also a line stage, again with upgradeable external power-supply options. Finally, as if that weren’t enough, each audio chassis is available in an EXD version, featuring upgraded components, copper chassis parts and cryogenically treated transformers -- as well as with the (separate) variable gain input and front-panel volume-control option.

So to recap, if we take the example of our P20 review unit, it is available in standard configuration or the EXD version, with one (if you include the P21 option) or two standard or EXS supplies -- making for eight configurations in all, each upgradeable to the next, with the P20 EXD EXS reviewed here representing the top of the P20 tree. You might be wondering just why BorderPatrol should offer three ostensibly similar amps all based on the same 300B tubes, but actually, given the purist nature of their customer base, the option of single-ended, parallel single-ended and push-pull output stages makes considerable sense, especially given the doubled-up output power of the S20/P20 options. Each amp offers its own particular blend of musical strengths and weaknesses, as well as preferred partnering systems -- a world away from the dubious pleasure of the switchable triode/pentode output stages you find on some amps.

With three amps, two component/parts levels and two power supplies that can each be used singly or in pairs, the BorderPatrol range offers users the ability to mix and match the ingredients to match their musical tastes, system and budget requirements. What might look confusing and alien at first (customers can, on the whole, stretch to the concept of monoblocks, but three chassis for two channels?) is in fact incredibly logical -- and only possible because the no-nonsense approach has dispensed with compromises that other products take as given. BorderPatrol might sacrifice the practicality and aesthetic elegance of single-chassis construction and machined casework, but it’s hard to argue with the sonic benefits that accrue.

Anybody totting up the parts and drawing sonic conclusions about the BorderPatrol P20’s expected sound is likely to find those suppositions rammed rudely down his throat -- assuming he is unwise enough to voice them, that is. Expectations of lush warmth and cuddly sound will be banished along with the first notes that issue forth. What BorderPatrol does to the 300B should be the envy of diet-food manufacturers everywhere. I can almost see the ads. In the "before" shot you see the familiar, rounded, bulbous shape of the vintage tube -- and the vintage sound that goes with it, all rosy glow, soft edges and soggy bottom. In the "after" you see an athletic, solidly muscled musical athlete. It’s as if a decathlete has just stepped out from inside a fat suit.

Forget prior knowledge and the prejudices that go with it. Forget that this is a 300B amplifier. In fact, forget that it’s a tube amp, period. Speakers driven by this amplifier (and believe me, driven is the word) produce a sense of solid, planted musical presence and purpose that makes you realize just how thin and insubstantial most electronics sound. Of course, one aspect of the 300B’s performance is the shape and body it lends instruments, but what really sets the BorderPatrol amp apart is not the sound of the performance but its mode of arrival. Take the sense of color, texture and harmonic identity that you hear from a great 300B amp and combine it with the sort of speed, agility and explosive dynamic response that you see as a sprinter leaves the blocks or a boxer with really fast hands delivers a stinging combination and you’ll get some idea of the sheer presence, immediacy and musical impact these 20 watts can deliver. This is music with pace and intent, performance with purpose and attitude. But behind those more obvious attributes lies a quality that is more subtle but ultimately more critical: absolute authority.

Now, there’s a term to conjure with. Like most terms appropriated by the audio industry to try and describe the performance of its wares, our meaning is more oblique or suggestive than the dictionary definition -- which is particularly ironic given the term under discussion. So let’s pin down exactly what it means when applied to the P20.

If music is a pattern, then we should be able to plot it on a graph, time on the horizontal axis, amplitude on the vertical. Indeed, that’s exactly what happens when we measure a signal or look at it on a scope. But it’s also what happens when we listen to it. The sense of the music is encoded in that pattern of notes, how loud they are, their pitch and spacing. As we listen we are constantly assessing the gaps, the steps in pitch or level between one note and the next and how long each step takes. Rather like with stepping stones, you can judge the position of the next from the one you’ve just left -- but only if you know exactly where that one was. If the system producing the note fails to track its leading edge, any shift in level or reflect its shape or decay (distribution of energy), then its point on your mental trace will shift -- which will in turn alter the perceived step to the next note. Alternatively, you can compare the location of each note against a fixed reference -- the axes of your mental plot -- assuming that they are stable. In practice, we actually do both. Our brain is clever enough -- and the signal it receives is so messed up -- that it needs all the help it can get. Just bear in mind the variability in the system creating the sound that we have to decode -- and particularly the speakers.

Look at the impedance curve of a speaker and consider for a moment what it’s actually telling you. As the impedance drops, the amplifier needs to supply more current to achieve the same level. Given that the impedance plot of almost all speakers varies with frequency, that presents the amplifier with quite a challenge -- one that’s hard enough to meet under static, constant level conditions. But a musical signal doesn’t just vary in frequency; it shifts -- often dramatically -- in terms of level and density. So the amplifier has to respond to both a shifting load and a constantly varying demand. Think back to our stepping stones and that’s the equivalent of trying to move along a string of small floating rafts in a high sea -- and that’s before we even get to the issue of phase shift through the crossover!

Which brings us back to the definition of authority. In musical terms it refers to the ability of the amp to keep those rafts stable, securely anchored despite the "waves" trying to pull them this way and that. In electrical terms that’s all about the amplifier’s ability to respond to both the signal and the schizophrenic character of the loudspeaker, not just to respond to the shifting levels and power demands, but to do it quickly enough that the timeframe for each note stays in place.

There’s actually a lot more to it than that. As well as phase issues and acoustics, the amplifier has to work with the signal it receives (which helps explain why something as apparently simple as a line stage can have such a profound impact on the musical integrity of a system). But the bottom line here, at least as far as the power amp is concerned, is that it needs to be able to meet the simultaneous dynamic demands of the signal and the speaker -- and above all, it needs to do it quickly, which is where the problems really start. On paper, the answer to the dramatic shifts in demand can be provided by unlimited headroom and bottomless reserves of power -- except that those things involve their own compromises. Multiple output devices introduce tracing errors, while monster reservoir caps take time to empty -- and that’s before you get to the parasitic signal and mechanical issues that are exacerbated by using larger numbers of bigger components. As with all things audio, the answer lies in achieving a workable balance, in this case between the nature of the signal, the power delivery of the amplifier and the load presented by the speaker. Get that right and the amplifier’s ability to respond to the signal while meeting the speaker’s demands will mean that more notes spend more of their time just where they should be, making the pattern easier to read, the musical message more intelligible and the performance more effective. That’s musical authority, and the P20 has it in spades!

In any discussion of musical purpose and attitude there’s no better place to start than P. J. Harvey. In deference to the more sensitive souls in the audience I’ll look at her more accessible material, the 2010 album Let England Shake [Island 2758997], a typically thoughtful and provocative piece. The undulating, almost simplistic melody of the title track underpins the soaring Kate Bush-like vocals, creating a repetitive, almost hypnotic effect, but note how the track shifts almost imperceptibly to something darker and denser. The combination of dense presence and motion, the easy, effortless separation of the elements are your first clues to the P20’s considerable musical impact. Move on to "The Last Living Rose" and listen to the way the subtle texture of the understated drums is clearly apparent, despite being recessed in the mix. Note, too, the instantly identifiable character and textural separation of the solo instruments, the tenor sax and the gentle cascade of the descending guitar lines. It’s a quality that carries over to "In The Dark Places," the grunge guitar and drum contrasting with the purity and soaring clarity of the vocals, held together by the absolute security of the extended rhythmic figure.

You get the picture. The whole album is an object lesson in the creation of dense swirling textures and stark contrast, between the muddy congestion and grain of the backing tracks and the illuminated, almost spot-lit clarity of vocals and solo leads. It’s a high-risk strategy, with the sheer density threatening to overwhelm proceedings, dragging the whole thing down into an impenetrable mess -- as so often happens on lesser systems. The constantly changing pitch, level and density of the music make keeping things separate and organized a real trial, especially given the intrusion of Harvey’s characteristic edge and attack. But with the BorderPatrol amp doing the driving, it’s not just the solos that stand proud, the density of the backing and its interlocking textures are also laid bare, making the gradual shifts in its depth, nature and its rhythmic development instantly apparent, the slow evolution of the tracks’ feel and mood all the more effective, the contrast with (and impact of) the main message that much more apparent. Nothing else sounds quite like P.J., and nothing else makes that quite as obvious (or musically engaging) as the P20, its easy authority taking the stress out of deciphering the recording and putting the onus firmly on appreciating it.

It’s an object lesson in just what I was describing -- the ability to keep everything in its place, both in terms of level and time. In turn, that comes down to the amplifier itself and the quality of its power supply. Of course, at 20 watts rated output, the P20 is hardly a powerhouse, but contrast that number with the combined weight of its power supplies -- a cool 160 pounds, most of which is ironwork rather than reservoir capacitance. Perhaps it's not surprising that the BorderPatrol amps work from an audibly firmer footing than most.

You’ll notice that I keep referring to the textural definition or distinctions between instruments and voices. The P20 gives each instrument and singer its own identifiable voice, but this separation has more to do with nature and harmonic identity than spatial separation and transparency. Oh, there’s depth, breadth and height to the soundstage, a palpable sense of acoustic volume, but it’s not the kind of airy, walk-in soundstage so beloved of high-definition, high-end equipment and speakers. Try walking in to this soundstage and you’ll have to fight past the music coming the other way. Play Polly Harvey’s The Falling -- B-Sides 2001 -- 2008 [PJH 0108], definitely from the other end of her musical spectrum, and despite the minimalist instrumentation the BorderPatrol amp delivers a properly visceral experience. Play "Kick It to the Ground" and approach at your peril! What you have here is the microdynamic definition and speed of response that give tube amps their characteristic sense of presence, backed up by the kind of substance that comes from deliverable power launched from a really firm base. Which is why sprinters use blocks and a boxer’s power comes from his rear foot. When the BorderPatrol produces music it doesn’t sound like that music is appearing out of thin air -- it really is locked in time and space. And if it gives such physical presence and substance to one girl and her acoustic guitar, think what happens when you give it a whole orchestra to play with.

If you want really over-the-top orchestral music, the place to look is definitely film scores, examples being legion, from Gladiator and Thin Red Line through Gravity and Hunt for Red October, any one of which will likely introduce your woofers to their end-stops if you get enthusiastic with the volume control. But the example I chose was the Glory soundtrack LP [Virgin/Classic Records VR 91329] that mixes a huge orchestra with plenty of drums and the Boys Choir of Harlem. You want big and powerful, you’ve got it. You want stability and control, dynamic grip and a soundstage that stays put -- you‘ve got it. The whole second side of this album sweeps between solo instruments or voices, the rattle of side drums or distant trumpets and full orchestral/choral crescendos with chimes, gongs and organ thrown in. The P20 takes it all in its stride, allowing this majestic music to sweep you along, while never allowing the patriotic bombast to obscure the haunting sub-text. It’s a deftly balanced performance that remains secure and sure-footed despite the dynamic and artistic excess on show.

By now, the more perceptive of you will be wondering what speakers were doing duty while all this musical energy was exploding into my listening room. After all, having made the point that it’s all about achieving balance within the system, shouldn’t that be a primary consideration? Absolutely! You can all go to the top of the class and feel suitably smug about it. So just what were those speakers? The massive and massively expensive Living Voice Vox Olympian five-way horns, including the active, horn-loaded Vox Elysians? Well, you might well think, a full-range horn system with active bass and 109dB sensitivity (not to mention a wince-inducing price tag) darned well should deliver the goods -- even with 20 watts. But what about Crystal’s diminutive 87dB efficient Minissimos? Or the full-range and ceramic/aluminum-drivered Coincident Pure Reference Extremes? Or the Focal Scala Utopia V2s? None of these look like perfect partners for a 20-watt, 300B amplifier, yet each produced stunning results, redolent with the sheer musical substance and authority that the P20 seems to generate so effortlessly. Indeed, I spent more time using the amp with the Focals -- arguably the least likely match, with their combination of wide bandwidth and reactive, 4-ohm rating -- than with any of the others. It was a spectacularly effective combination and the source of most of the musical examples I’m citing here. Yet what was also surprising was just how consistently the character and merits of the BorderPatrol amp shone through, irrespective of partnering speaker. This is an amp that doesn’t just drive a speaker, it will also drive a lot of different speakers. Frankly, anything the right side of 90dB and you’ll be cooking with gas. It’s quick enough with sufficient dynamic integrity and agility to rise to the challenge of a really high-quality, high-efficiency system like the Vox Olympians, but it’s real métier lies lower down the efficiency range, with the mid-90s proving particularly fruitful -- nice, given the sheer range of really good speakers that are edging towards that realm. Coincident, Focal, Reference 3A, Paradigm and the smaller Living Voice Avatar models are just the tip of the iceberg, with plenty more alternatives to choose from.

As remarkable as the P20’s performance is, it’s not entirely without precedent. The Lamm ML2.1 monoblocks (now ML2.2) offer some striking similarities, not least the power rating, physical bulk, enormous power supplies and price. The Lamms also deliver astonishing musical authority and have a reputation for driving awkward speakers. Comparisons between the two amps are interesting, albeit prone to the fickle lens of memory, but I’d characterize them as follows. The Lamm offers a broader tonal palette with richer instrumental hues and a more obviously transparent and spacious stage. What it can’t do is match the absolute authority of the P20, or its ability to really grip a speaker, irrespective of the musical demands. So, although Lamm demonstrate the '2.2 at shows with Wilsons, the scale of the material played is strictly limited -- I remember asking at one show for something musically larger and being offered a Schubert chamber piece. No such concerns inhibit musical range with the BorderPatrol.

It’s a comparison that also neatly raises the issue of which BorderPatrol amp offers what. I deliberately chose the push-pull P20 because experience suggests that push-pull amps deliver the superior immediacy and dynamic integrity that I value. When it comes to tonal color (as opposed to textural character), the P20 is no slouch, but it is bettered by the Lamms and if that’s your bag, then the S20 is the amp you should be looking at, while once you get beyond the 96dB sensitivity mark you are definitely entering S10 territory. Those demarcations aren’t set in stone, and I’ve heard the S10 deliver superb results from the 93dB Living Voice Avatar OBX-R2, but they will serve as some sort of guide -- as well as underlining that, in the case of the P20, the absolute authority it exhibits is down to the output topology as well as the power supplies. You pays your money and takes your choice, but at least it’s a choice you have.

If scale and presence, stability and authority are displayed by any one instrument, then it’s the piano. Just as it serves to illustrate the specific qualities that well-executed direct drive can bring to a turntable, its physical size, complexity and low-frequency extension test the evenness of any amplifier’s textural and harmonic resolution. Maybe it’s to do with the sheer weight of the instrument. It’s no surprise to hear a cello move, or a singer, but pianos should stay put, and it’s incredibly obvious when you hear a system that does just that -- mainly because so many don’t.

One of my favorite Basie albums has always been Farmer's Market Barbeque [Analogue Productions/Pablo 2310-874], partly for the brass dynamics and punch, partly for the tight playing of the well-drilled band, but mostly for the incredibly subtle work of the rhythm section and the Count’s piano in particular. Sparse and understated, his deft contributions are all attack rather than level, stabbed interjections that establish the pace or nudge the track this way or that. The halting staccato piano phrase that opens "Beaver Junction" is a typically understated microcosmic masterpiece, the right-hand/left-hand switches beautifully timed and balanced. It instantly establishes both the nature and the tempo of the track, not slow -- but not too quick, before slowly but inexorably speeding things up, something that has never been quite as explicitly stated or emphatic as it is on the VPI Classic Direct Drive and the BP P20. The BorderPatrol anchors the sound of the piano in space, giving it a very real (in the true sense) weight and sonority. The dynamic contrast between right and left hands, the precise shaping of this fractured musical fragment establishes exactly who is running this show, just as the slow smooch tempo of "St Louis Blues" is dictated by the Count’s meandering, seemingly aimless but perfectly paced lines, the fluency of his relationship with bass player James Leary.

That control over the temporal domain (both the Count’s and the VPI 'table’s) is meat and drink to the sure-footed and planted presentation of the P20, giving the music, the band and above all its leader an inexorable musical momentum and purpose. Basie’s command is absolute, his authority complete, a case of sonic authority reaching the higher plain of the musical -- but that’s exactly what the BorderPatrol amp is all about. When I describe its sound as solid and planted, I don’t mean static or rooted. It’s all about the foundation that underpins the amplifier’s dynamic response, the life and urgency, the drive and propulsive energy it reveals in the recording and performance, being able to jump when the signal calls for it without even waiting to ask, "How high?" Or not, because let’s not forget that stopping is every bit as important to starting when it come to the great scheme of things. That temporal security is just as crucial to the constrained weighting, restraint and the control required to measure a slower tempo or balance an orchestra against a soloist. As impressive as the P20 is when it comes to up tempo pieces and dynamic punch, it’s the way it keeps quieter, slower passages moving forward without any hint of dragging feet or lagging lower registers that really reveals just how evenly this amp delivers its energy across the entire musical spectrum. It’s a quality that, along the way and without any fanfare, reveals not just the shape of the music but possibly the P20’s single most important asset, the ability to unveil the human shape of the performance.

If the acid test of musical integrity is the ability to identify the contrasting character of multiple readings of the same work, then it’s a test that the BorderPatrol aces. Its effortless grasp of tempo and the accuracy of its dynamic tracking cut right to the heart of any conductor’s arsenal. So comparing Karajan’s ’62 reading of Beethoven’s 6th Symphony [Deutsche Grammophon Gesellschaft SKL 1/8] to Bohm’s later reading with the Vienna Philharmonic [Deutsche Grammophon Gesellschaft 2530 142], the difference between HVK’s clumsy, hectoring tempo and overly sudden dynamic shifts and Karl Bohm’s temporal control and grace is almost brutally apparent. Where Bohm lets the music swell and breathe, Karajan has his boot on its throat. If ever two records demonstrated the musical virtues of the velvet glove that wraps the BorderPatrol’s iron fist, then these are they. Likewise, listening to the Goss Guitar Concerto (John Williams and Paul Daniel conducting the RPO, [John Williams JCW-3]) the acknowledged influence of Elgar’s shade over the structure and tonality of the second movement is utterly unmistakable, the composer’s art rarely laid so bare -- or his point made with such aplomb.

Look back over the musical examples I’ve used and you’ll see that they run the gamut, both in terms of scale and genre, from one-take raw recordings of girl and guitar (with a snarl), through jazz and classical to the world of the film score. With the possible exception of the Basie, none of these recordings is exactly audiophile -- in fact, quite the opposite. Which brings me to what is my final and in some ways most important observation about this BorderPatrol amp -- it starts with the basics and builds from there. The P20 is all about the fundamental -- be that in terms of pitch, structure or dynamic discrimination. If you want to hear the drummer’s shoe laces bouncing as he taps his feet, there are amps and systems that will do that for you. If you want to glory in the sheer harmonic beauty of renaissance choral music, losing yourself in the lush, interleaving harmonies, there are amps and systems that will do that too. But if you want to know what makes this noise music -- any music, irrespective of type or recording quality -- and what makes it worthwhile (really, really worthwhile) then there are few better tools than a BorderPatrol. If what the drummer is doing with his hands and how it relates to the rest of the band is more important to you than his footwear; if the structure of a choral work and what is being sung matters more than the wash of reverberation from the vaulted ceiling church acoustic; if you want to know why whoever wrote the music you are hearing bothered to put pen to paper, or why the musicians bothered to record it, then the P20 will come as not just a breath but a gust of fresh air, well and truly dispatching the audio cobwebs. It is all about the why rather than the what, the sense in music rather than the surface details of the recorded artifact, what hi-fi should be rather than what it has all too often become.

That honesty does come at a price, both monetary and musical (although BorderPatrol amps start at a considerably lower cost level than most of the competition, and even an EXD EXS looks cheap compared to many of the alternatives). But what the P20 might eschew in terms of sheer rose-tinted beauty or absolute resolution it more than makes up for, at least in my mind, in terms of dynamic and rhythmic nuance, musical shape and structure. It gives the music a voice and lets it speak. The Yorkshire-born have a reputation for being a direct and no-nonsense folk. It’s a characteristic that has been instilled in this amp, tempered and buttressed by the artistic sensitivities of the more bohemian Brighton, creating a whole that’s even more musically powerful and engaging than the sum of those parts. This is no "tube-mids meets solid-state control and bass" lash-up. It is something altogether different and more significant. Like the Berning Quadrature Z, it is gloriously defiant of sonic categorization, offering its own compelling and penetrating perspective on the musical performance. It speaks with a musical voice that’s hard to ignore and easy, oh so easy, with which to engage.

Make no mistake, the P20 EXD EXS is a demanding, attention-grabbing, domineering presence in your system, but that’s ultimately what makes it so communicative and satisfying. Listen to a BorderPatrol amp and that degree of musical insight could well come as a shock -- in either the positive or negative sense. But one thing this amp won’t do -- and something I really like and respect it for -- is leave you wondering.

Price: $25,750
Warranty: Two years parts and labor.

BorderPatrol
10340 Whittier Court
White Plains, MD 20695
(301) 705 7460
www.borderpatrol.net

Three boxes, but what's inside?

As I’ve stated, the BorderPatrol P20 doesn’t sound like other amplifiers and doesn’t look much like them either. But those two things are intimately connected. The P20 EXD EXS under review consists of three separate parts: an audio chassis and a pair of large external power supplies. The P20 chassis looks pretty sparse, with just four smallish transformers, four 300Bs and a pair of driver tubes disposed about its top plate. Its modest 39-pound weight reflects the wood-framed chassis (selected for sonic reasons as well as a begrudging Yorkshire nod to aesthetics) and the lack of mains transformers. So what are the four transformers up top? Two are output transformers (generously oversized with a 75W rating on a 20W amp), while the small dimensions of the others should be a giveaway, identifying them as interstage phase/splitter transformers used to drive the 300Bs. The pair of small nine-pin tubes tucked away behind the 300Bs are unusual 6DE7 dissimilar dual triodes, each with a medium- and a low-gain section. The medium-gain triode is used as the input stage and is capacitor-coupled to the low-gain section, which then drives the interstage transformer. This arrangement provides more accurate and stable output voltage than a tube phase splitter, while also being time-linear and feedback-free. The 300Bs run fixed bias applied through the driving transformer’s secondary windings. The mains transformer, input chokes and tube rectifiers are all accommodated in the large EXD boxes.

The top plate of the P20 chassis also houses the input/output socketry, ranged along its rear edge, with just a single pair of RCAs (no balanced-input option) and rows of three binding posts per side, allowing for 4- and 8-ohm connections. Two thick umbilicals with multi-pin connectors complete with screw collars connect the P20’s audio chassis to its slave supplies.

Once you pare a triode circuit right back to the bare minimum by removing the power-supply components, you can appreciate just how minimalist it really is, even in push-pull form. Just as that shines a stark light on power-supply quality it is equally critical of the individual components used throughout the circuit. Attention to detail inside the P20 is exemplary, with carefully selected parts from the usual audiophile suspects, although each and every component has been individually assessed, rather than simply "drunk by the label," with the EXD mods adding a copper top plate, cryogenically treated transformers and high-quality film-type bypass caps to the mix. That almost obsessive care and attention are perhaps best represented by the ironwork: both the interstage and output transformers are sophisticated oversized multi-section designs wound from high-purity copper onto M6 silicon-steel laminations -- expensive but with real benefits in terms of high-frequency air and extension, low-frequency control and freedom from saturation. In either case you could build a simpler, perfectly serviceable and far more affordable audio transformer to do the same job -- it just wouldn’t sound as good.

If the audio chassis is stark in its simplicity and surprising for its low weight, the dual-mono EXS power supplies are the complete opposite. Squat and compact, with an internal well that houses the three horizontally disposed rectifier tubes in a cooling chimney, each chassis is heavy enough at 80 pounds to make you wonder whether it’s simply a box full of ball bearings. These are heavy -- heavy enough to think twice before lifting them on your own. While it's easy to look at the P20’s main chassis and wonder why it costs so much, sit it on top of the power supplies (not recommended for listening!) and the material content suddenly seems pretty impressive, with a total weight that’s just a hair shy of 200 pounds backing up the 20Wpc rated output.

The standard BorderPatrol supply features a massive 248-lamination AC transformer feeding three independent choke-input, tube-rectified supplies. A GZ37 feeds the 300Bs, with an EZ80 each for the driver tube and negative bias supply. It is built into an aluminum chassis and weighs 33 pounds. The EXS uses two of the AC transformers in a novel arrangement that Gary Dews claims is unique to BorderPatrol -- which is why he doesn’t want to discuss it. The 300B choke is physically larger with a higher inductance, while the whole thing is built into a heavy-gauge copper chassis, weighs 80 pounds and is cryogenically treated. The EXS is interchangeable with the standard supply(s) on any of the amplifiers.

How does all that stack up in terms of pricing? Owning a BorderPatrol push-pull 300B amp can take many forms, but the basic options are as follows.

P21 (single standard PSU), $9750.

P21 with EXD upgrade, $12,750.

P21 with EXD upgrade and EXS PSU, $17,250.

Upgrade from P21 to P20 (including extra standard PSU), $4750.

P20 (with dual-mono standard PSUs), $13,750.

P20 with EXD upgrade, $16,750.

P20 with EXD with dual mono EXS PSUs, $25,750.

These prices are for new units. The cost of upgrading from one level to the next will not match the cost difference between new units and will depend on any trade-in allowance for standard supplies if upgrading to EXS units.

-Roy Gregory

Associated Equipment

Analog: VPI Classic 4 turntable with SDS; VPI JMW 12.7 and Tri-Planar Mk VII UII tonearms; Lyra Titan i, Scala, Dorian and Dorian Mono cartridges; Clearaudio Goldfinger Statement cartridge; van den Hul Condor cartridge; Allnic Puritas and Puritas Mono cartridges; Nordost Odin tonearm lead, Lyra Connoisseur 4.2PE phono stage.

Digital: Wadia S7i and GWSC-modified 861SE CD players, dCS Paganini and Vivaldi transports, DACs and uClock.

Preamp: Connoisseur 4.2 LE.

Power amps: Berning Quadrature Z monoblocks, Jeff Rowland Design Group Continuum S2 integrated amp, VTL MB-450 Signature Series III and MB-185 Signature Series III monoblocks.

Speakers: Coincident Speaker Technology Pure Reference Extreme, Focal Scala Utopia V2, Living Voice Auditorium IBX-RW, Marten Coltrane Supreme 2, Raidho C1.1, Wilson Benesch Square Five.

Interconnects and speaker cables: Complete looms of Nordost Odin, Valhalla 2 or Crystal Cable Dreamline Plus from AC socket to speaker terminals. Power distribution was via Quantum QRT QB8s or Crystal Cable Power Strip Diamonds, with a mix of Quantum Qx2 and Qx4 power purifiers and Qv2 AC harmonizers.

Supports: Racks are Hutter Racktime used with Nordost Sort Kone equipment couplers. Cables are elevated on Ayre myrtle-wood blocks or HECC Panda Feet. Nordost Sort Füt units were used under the speakers.

Acoustic treatments: As well as the broadband absorption placed behind the listening seat, I employ a combination of the LeadingEdge D Panel and Flat Panel microperforated acoustic devices.

Accessories: Essential accessories include the Audio System SmarTractor protractor, a USB microscope and Aesthetix cartridge demagnetizer, a precision spirit level and laser, a really long tape measure and plenty of masking tape. I also make extensive use of the Furutech anti-static and demagnetizing devices and the VPI Typhoon record-cleaning machine. The Dr. Feikert PlatterSpeed app has to be the best case ever of digital aiding analog.