On The Road: A Visit To BorderPatrol

What is an audiophile?

Good question, but more interestingly, how do you think your friends would answer that question? Okay — don’t answer that [shudder].

Back to you — what’s your mental picture of the stereotypical audiophile? Take a second and fix it in your mind. Got it? Now, pivot your mental camera and point it at his system. What does it look like?

I’ll bet you dollars to donuts, it’s a tube system. Probably SET. Paired with a single-driver, high-sensitivity loudspeaker.

Why is that? Why is that the image many audiophiles carry — of other audiophiles? Personally, I don’t know. It’s a cult thing, I’m pretty sure. Like it or lump it, but … there is a reason.

Backstory

I’ve been listening to Gary Dews’ amps at audio shows for a couple of years now, starting with a trip to the Capital Audiofest back in 2010 with my 3 year-old twins (gotta start ’em young). But based on that experience, I came away with an alarming sense that I had just mis-spent a rather large amount of money on other gear. This nagging sense of mis-adventure persisted right up until this past summer, where I cemented that with the early conviction that I’d pretty much fucked up entirely — Gary loaned me an amp and a pair of his Living Voice loudspeakers for several weeks while he was on vacation. To date, this brief interlude remains one of my favorite audio explorations.

So, who’s Gary?

Gary Dews is the man behind BorderPatrol, and he’s been making audiophile gear (and yes, I mean gear that would fit in that stereotypical image you may have of “the audiophile”) for the last 20 years. Gary’s British, but he moved his family and operations to the USA back in 2005 — just enough time to get settled in before the financial collapse. Yikes.

But all that was several moves down the line. I asked him how the ball started rolling, all those years ago:

I met these two guys at college, both called Guy, who were designing record players. After college, they formed a company called Voyd Turntables that made excellent record players with innovative two and three motor drive systems. The fact that people I knew could do this sort of thing really demystified hifi for me.

Guy Sergeant later went to work at Audio Innovations tube amp company in Brighton UK and I bumped into him one Saturday afternoon when I was touring the local hifi shops. He was running the retail side of Audio Innovations. The store had A.I. tube amps, a couple of pieces from Audio Note (Japan), Snell Speakers, Voyd Turntables, Systemdek, Audio Note (Japan) silver cable etc, very esoteric in a time dominated by Linn and Naim.

After meeting up with Guy again, my day job as a pharmaceutical research chemist, which I had already grown bored with, became intolerable and it was only a matter of time before I left and got into the business. My 1st entry into the world of hifi was as a retailer heading up Definitive Audio Brighton selling Voyd/A.I./Snell systems and associated products.

Audio Innovations? I hadn’t heard of Audio Innovations, so I asked Gary about the particulars and how he’d gotten mixed up with them.

AI was a Brighton UK based tube amplifier company headed by the pre-Audio Note version of Peter Qvortrup. PQ later left to set up Audio Note and the AI company folded in the mid nineties.  This company resurrected the market for tube amplifiers in the UK in the late 80’s offering great sounding, great looking, great value tube amps. Some of their amps were really ‘out there’ for the time: Take the Audio Innovations 1st Audio Amplifier, a 7.5W/ch 2A3 amp that cost $2250 in 1989 for instance, and the 2nd Audio, 15W/ch 2A3 mono-blocks for $4500. Back then, that was radical stuff! The company got a huge amount of positive press. Lots of the UK reviewers were using the amps in their own systems. It was an exciting time.

Sometimes, I get lucky, so I kept asking questions — starting with what happened to take him from selling to making. He said it was pretty simple — he got curious, and, well, that’s never good. Guy Sergeant made a trip to Denmark to visit Tommy Hørning; he came back raving about the importance of the power supply — that is, the high voltage supply that feeds the circuit, an intrinsic part of the amplifier or pre-amp, not what comes from the wall or a cleaner/purifier. Guy built a few PSUs and attached them to various amps and pre-amps, and Gary had his “a-ha!” Gary took a trip to “the depot” with another friend, Kevin Scott (later of Living Voice), and they bought an old Solartron power supply for $75 … a great deal … but, of course, they still had to figure out how to lift it. This PSU was a tube-regulated unit, massively overbuilt, and packed with audiophile goodies like tube rectifiers and paper in oil power supply caps and when hooked into an Audio Innovations amp, the sound … was … [cough] … revelatory. From there, it was all PSU, all the time.

Gary wondered if it was possible to make a commercial, “audiophile”, version of the Solartron — and a hundred different prototypes later, he decided that a $3,750 power supply for a $800 amp was probably not a product, at least not in the commercial sense. Lots of experience, lots of trial and error, but nothing he could actually sell. But in 1993 Kevin Scott tells Gary something to the effect of “I’m showing at the London Hi-Fi Show with my new Living Voice Tone Scouts — make me something better than these here amps.” A challenge? In essence, yes — and the result was the first BorderPatrol amp.

The 1st amp I made was a 300B single-ended (quell surprise!). It had a tube rectified choke input filter PSU  (quell surprise deux!) and sounded great but the choke buzzed like a bastard and it had way too much output noise. I (very) temporarily converted the PSU to capacitor input, which solved all the noise issues but elicited the comment ‘no longer suitable for audio work’ from one of my colleagues. It was quickly changed back!

That amp had many of the design features I still use today though all of them have been improved and refined over the years. It did not have an external PSU or inter-stage transformers and it had a steel chassis but it was great start, and it did elicit some orders. Not long afterwards, the 1st BP allowed out in public appeared at a hifi show in London with Living Voice horns.

Oh, and in case you were wondering, the name “BorderPatrol” is something of a joke. Obviously, he needed something other than “random amp from some dude”. A name was required, even if it was just for a one-off, a throwaway. So, what to call it? Something different, obviously. Something off the wall. With no real aspirations at this point, the only real requirement was a name without the word “audio” in it (think, “Audio Note”, “Audio Innovations”, &c). But an off-hand comment by Kevin and Gary had something that was all of that, and memorable to boot — and a name that pulled in quite a few comments from the press. BorderPatrol, the company, was born.

His first commercial product was, perhaps not surprisingly, a power supply. Pulling the PSU out of the prototype 300B amp he used at the London show and plugging it into an Audio Innovations amp, grins went all around. This was good. And more importantly, he could do it for $900. He had a product.

The 1st SET amps were great test beds for trying out different approaches:  fixed bias vs cathode bias, anode follower vs cathode follower, capacitor coupling vs inter-stage tranformer, tube rectifiers vs  solid state etc, etc.

Whilst it is possible to make nice amps with solid state rectifers, tube rectifiers always sound sweeter, more musical and more natural. The sound is more real and less hi-fi.

Once you decide that tube’s the way to go, there are two ways to do it: capacitor input, or choke input.

The capacitor-input design, which is by far the commonest approach used with tube rec’s, I discarded because of lousy voltage regulation. It can’t maintain a constant voltage as the load presented by the music changes. When the amp needs to do some serious work, for instance with large transients or a succession of heavy bass notes, the supply collapses, exactly when you don’t want it to. That manifests in the all too familiar early compression and out of control bass. You have no choice but to turn it down or choose different music.

A choke-input design has much better regulation. It’s stiffer. You can play a much more demanding music program. It provides a much firmer platform for the amp to work from.

But … it’s big. And expensive. And the approach required huge chokes that had to be very specifically designed and built to a very high level of quality or they are noisy. Such chokes also add lots of weight to a design and brings a rather hefty magnetic field … using them in the dead center of an amp might be suboptimal. But the voltage regulation was the best that could be had, and the sound was glorious. When he compared his design to the Solartron that got him started, he could hear the Solartron behind his SET amp.

The SET amp/Solartron combo had great sound and in some ways it bettered the choke input supply, but I couldn’t get the ‘Solartron’ types to disappear. It was like having two amps in the system, one working behind the other. I decided the tube rectifier/choke input filter PSU had the best overall balance of qualities.

His design was just more … pure. More transparent. More “everything” that made the SET experiment interesting in the first place.

Time to productize. From 1993-1997, this was the game for BorderPatrol — PSUs.

The dynamic limitations of tube amplifiers are mainly a result of soft high voltage supplies which collapse when working hard causing early compression, lack of composure and over-blown, loose bass.

The BorderPatrol PSU provides a stiffer high voltage supply, tightening the bass and improving the overall dynamics and power delivery of the amplifier. Your tube amp will now remain in control on complex musical passages and reveal interplay between musicians that was previously blurred and ill-defined. The effect is as though the amp went away to a fitness farm and came back 40lbs lighter, stronger and more athletic.

Most high voltage supplies provide little or no (RF) noise rejection, and many actually create noise themselves. This noise pollutes the noise floor, burying vital micro-dynamic information and dirtying the tone. The BorderPatrol PSU uses noise free tube rectification and a high inductance choke to kill RF and produce a pure, clean supply.

Almost all tube amplifiers will be substantially improved, including those that already use tube rectifiers and chokes in their power supplies.

Tough words — and, interestingly, backed up by a series of reviews from HiFi+, by Alan Sircom, Roy Gregory and Jason Kennedy.

It was curiosity, and a perhaps a little desire to do more than mod, that led him to build his first commercial amp (post London Hi-Fi show), a design that’s evolved into the currently-available SE300b. A push-pull design came about 5 years later (in 2002) to satisfy the demand for a higher-output amp; a parallel SET followed about 6 months after that. Interestingly (at least to me), all were based on 300b tubes.

I think many of us feel that “The Problem” with SET amps is the low output. The sound is great, but what loudspeakers will they really work well with? The answer is “not many”, of course, but sheer SPLs aren’t the only problem. I asked Gary about the 845 tube, a higher-output tube that can still be run single-ended, and why he chose a 300b instead of it or one of those other highly-regarded higher-output tubes. I was thinking about bass performance, particularly, as I know the 300b tube is notorious for its big, loosey-goosey bass. I was thinking about treble response, also, because no one in their right mind would ever call a 300b tube particularly extended. In fact, I was carrying around a lot of “thinking”, and pretty much convinced that the 300b tube is exactly the wrong tube to use in an amp — not just for my taste, but for anyone not using some frequency-compromised single-driver loudspeaker. Gary, took all this in with a somewhat gnomic smile and proceeded to help me untangle some of my audiophile mis-/pre-conceptions.

The 300B is a much maligned device, but it’s not the tube’s fault. A 300B is very linear and can be operated without negative feedback. It gives a healthy power output from a relatively low voltage supply meaning designing a great PSU for it is possible. Output transformer design is relatively straightforward compared to things like 211’s. It has a lot of things going for it.

Unfortunately the ‘classic 300B design’ with cathode bias and tube rectified capacitor-input PSU (which is what everyone makes for reasons of cheapness and tradition), has given rise to the opinions of what constitutes Classic 300B sound; loose flabby bass, pathetic dynamics, and rolled off treble.  But put it in a better circuit with a stiff PSU and it’s a different ball game.

….

In a well designed tube amplifier, the output transformer defines the frequency response and the inductance of the output transformer defines the low frequency extension.

The inductance required to generate any particular frequency is proportional to the impedance of the driving tube. This is 700 Ohms in a 300B vs 1700 Ohms in a 845. Therefore a 845 amp output transformer will need approx 2.5 times more inductance to produce 20Hz than a 300B transformer will.

To produce this inductance more turns of wire and more metal are required. A lot more of both, so an 845 output transformer must be big. This has implications at the other end of the scale. More turns equals less high frequency unless very fancy techniques are used.

All BorderPatrol output transformers are designed for a full power -3dB point below 10Hz. That’s why they are so big relative to the power output of the amps. Very few, if any, 845’s will get close to that. And the BP designs are sectioned to go high as well.

….

I prefer the sound of triodes to tetrodes and pentodes. The 50W Class AB 6550/KT88 design is very popular and works for a lot of people but it’s too compromised for me. I prefer the smoothness of Class A operation and being able to operate without negative feedback brings forth resolution and realism that those designs can’t match.

“Sectioned” — an interesting word, and one I’ve heard him reference a couple of times. The first thing to know is that transformers aren’t just a bobbin with a ginormously long wire spun around them. They’re bobbins with with wire spooled around them, yes, but there are arranged in sections . If it was one giant wire, you creat a giant capacitance, called inter-winding capacitance, and that’s bad — what you’d hear is a whole lot of nuthin’ in the treble. You’d also create a lot of leakage inductance, and that’s bad too — what you’d hear is a whole lot of nuthin’ in the treble (did I just say that twice?). However, by interleaving the primary and secondary sections, and insulating them one from the other, this capacitance & leakage inductance drops dramatically — and this increases your bandwidth. Most transformers used in high-end audio are sectioned — somewhere around 5-7 sections is typical. The ones Gary uses in his SET have 22 sections. Yeah, they’re custom.

So, what does this give you? Imagine, if you will, a 300b tube amp that can bring the shimmer of a cymbal and tinkle of a piano but that also doesn’t do bass like a farting cow. If you’re having trouble imaging this, no worries — let’s just say that I was dubious, too.

I borrowed a P21, a single-PSU push-pull integrated design, but as thrilled as I was by that amp, I was very curious what the other designs sounded like. So, I asked Gary if I could swing by to find out. Surprisingly, he said sure.

Roadtrip

Early October found me winding my way around the Washington DC Beltway and out to Waldorf, Maryland to Gary’s one-man shop. Having successfully relocated from the garage to the basement, Gary was starting the long, slow climb out back into the sunlight, so I got to see a couple of different setups.

Let me back up a second and talk about product line.

Gary makes three things: amps, preamps, and power supplies. He’s also just starting to make DACs, but lets leave that aside for now. The amps are all 300b-based, as we said. You can get them a couple of different ways.

Base

• Single-Ended (Models: SE300b/S10)
• Parallel Single Ended (Model: S20)
• Push-Pull (Models: P21/P20)

Options

• Any amp is available with a single outboard “stereo” PSU, or as a dual mono/dual PSU. The exception is the S20, or parallel SET, which is only available with the dual-mono/dual PSU option.
• Any of amp can be had as a stand-alone stereo amp, or as an integrated amp.
• Each amp has three levels of upgrade — base, upgraded (the “EXD” package), or cryo’d.

The EXD package, which is the big uplift, costs $3,000 at the time of order, but any amp can be converted after the fact for $4,250.

• Complete strip down and re-build of the amplifier into copper chassis parts.
• Changing the inter-stage and output transformers to cryogenically treated ones.
• Re-building audio the circuit with our preferred carbon film resistors.
• Any tweaks and detail changes required to bring up to the latest spec.

We started with a top of the line S10 EXD, a 9wpc dual-mono/dual PSU stereo amp, fronted by a BorderPatrol Control Unit EXT1 preamp with an external PSU. The loudspeakers were the Living Voice Avatar OBX-RW. The source was a custom/kit transport fed into one of his prototype DAC1 converters.

In a very rare treat, I got to hear this setup followed by a parallel S20 EXD. We finished the session with a P20, the dual-mono/dual-PSU version of the push-pull I had borrowed back in July.

Listening

First, let me say this — this is some of the best sound quality I’ve ever had a chance to immerse myself in. With that said, here’s what else I heard.

With the SET, the sound was stunningly clear. I spent a day with superlative Sunray loudspeakers from TIDAL Audio not too long ago, and in that session, I was treated to the most incredible and natural detail retrieval I’ve ever heard — until today. This amp, with these speakers and this source, was the most transparent I’ve ever heard. Ever. I heard things on this system I’ve never noticed before on my reference Chris Jones album, Roadhouses & Automobiles. I’ve talked about the “cricket test” before, and how on the title track “Roadhouses & Automobiles”, there are crickets buried 10dB or more down into the mix. On many systems, they’re lost. On good systems, you hear them in the opening sequence. The more clear they are, the more present, the more the system is able to put you outside on a summer night, the better. On the TIDAL loudspeakers, with that unbelievable Diacera diamond tweeter, you hear how the very first audible thing on this track is, in fact, crickets. It was eye opening, hearing that startling clarity — the first time, and every time. But here, on the S10 with the Living Voice loudspeakers, I heard the crickets everywhere through the entire track. Not just the opening sequence. Not just the closing sequence. But everywhere. I was gobsmacked.

More — the treble was clear and extended. I was just as clearly not listening to a 300b tube. Piano, triangle, cymbals … all fully captured, rendered, and separate. World class. The mid-range? Fuggedaboutit. This is a 300b after all — and for the record, we were using two different pairs of tubes for this session. The first was a spectacular pair of Sophia Electric Royal Princess tubes ($1,200/pair). The second was an even more spectacular Takatsuki TA-300b tubes ($2,000/pair). Both were unbelievable. Both were completely not what I expected out of a 300b-based system.

I was enthralled.

I suppose you could say that the the trouble, such as it was, came in the bass region. It is a 300b, after all. With a pair of these stock BorderPatrol PSUs, the bass was big and full and round — but also a bit loose. Did I mention this was an SET? Yeah. Well, I get it. Perhaps complicating things here, the loudspeakers are only 94dB — cranking the volume over into brain damage was totally possible, but the sound did begin to flatten at the highest SPL outputs. And no, the bass never got anywhere near “tight”. Real, sure — at least for an upright double-bass. But for deadmau5, Morcheeba or other stuff with electronically produced throbbing, complex low-end, this was clearly not the ideal pairing.

Moving to the S20 EXD, a parallel design with 18wpc of output, brought that all back in line. Bass tightened up. Midrange stayed locked. Treble remained extended. The sound here might have taken a small step back in overall immediacy. The detail and transparency might have been backed down a notch. I say “might” because I wouldn’t swear to either. In fact, the differences between the S10 and the S20 were pretty minimal — except for the bass. Reaching for an analogy, the hand on the bass was simply stronger. The reach? Deeper. The sound? Fuller. Again, looking at the 94dB OBX-RW, it may just seem obvious that an extra 9wpc would be “just the ticket” — and it was. I think this pairing really started to show what this loudspeaker can do.

That was pretty much picture-perfect, right up until we brought the P20 into the game. Now, YMMV — and I fully expect that it does and will — but for my taste, the linearity of the P20 was perfection. I really appreciated what the SET (and the parallel) brought to the table and it’s something — I want it. Oh yes, I do. But for what I do? For what I listen to? This push-pull amp was that “something else” that did all manner of audiophile cliche to Yours Truly. Oh me oh my.

Now, again, this is me talking about my tastes. The differences, at least as I was able to pick them out that day, came south of the treble, which was still clear, shimmery and extended. In midrange, things were more linear, perhaps a bit less immediate or immersive, but only in comparison. This is the downside — but again, it was only obvious in direct a/b comparison. Taken in isolation, I go the impression that the entire bandwidth simply seemed more “of a piece” — seamlessly continuous — with still spectacular 3-D imaging, roundness and rich, natural timbre. The mids just seemed to take a small step back. Not bad. Not detracting. Not distracting. Just different — still valid, still fantastic — but no, it wasn’t the same.

But that bass! If you’re a rocker, or like to play complex (electronica or orchestral) music, this amp knocked my socks clean off. 20wpc has never sounded this good. You want beat, bitch? Take it! Take it! Take it! Oh YEAH.

Okay, let’s break it down.

The S10 — a single-ended amp design with an innovative power supply — was as SET as I’ve ever heard, but with none of the SET downsides. That is, real, strong, fulsome bass with a clear and extended treble. Were I a betting man, I’d lay cash on barrel against this amps ability to put your preconceptions about SETs permanently to bed. At least, this is what it did for me.

The S20 — a parallel single-ended design — added mo’, betta, bass.

The P20 — a push-pull design — changed things up, as you’d expect. What it did was pure tube, but with great linearity and extraordinary bass. I think most “tube lovers” would cotton to this sound pretty much immediately as it has all the tube hallmarks. Great tone, great mids, but in a linear and resolved package.

My reaction? [Cough]. Clearly, I need two amps.

On a side note, Gary does seem to be working toward a new super-duper, paratrooper power supplies. At present, he’s being coy about whether or not such things may or may not see the light of day. If they work out, well, I’ll Be Back. I mean, what if a SET — with all of 9wpc — can crank as hard as a parallel amp? Ahem, indeed [insert drool here].

Wrap up

Many thanks to Gary Dews for the peek inside the kimono (as it were), just to see the whys and wherefores behind what he’s doing. It’s very cool to find a bespoke designer who’s taking a forgotten art and bringing it forward. Point-to-point wiring, OCD-level attention to detail and a meticulous approach to quality, using classic technology and bringing real, and really innovative, engineering solutions to traditional problems … okay, that’s a mouthful. But that’s BorderPatrol.

BorderPatrol will be showing with both Living Voice and Volti Audio at AXPONA in March and again at Capital Audio Fest in July. I should note, finally, that Gary does sell direct to consumers — if you’re interested in more information, or would like to schedule your own listening session, please contact him directly.