BorderPatrol SE300B-EXD Stereo Power Amplifier | REVIEW











Gary Dews is one of those people who is welcome at my home any time. He’s a wonderful guest and great conversationalist, and he always shows up with an unexpected and welcome gift! I don’t mean to patronize the guy here, but this last April, Gary made arrangements with me to pick up two items: the P21-EXD push-pull amplifier I’d just finished reviewing, and my BorderPatrol DAC, which was in need of a service call. What Gary hadn’t told me in advance was that he had something new in tow for me. This time, it was a variation on his original amplifier design, now dubbed the BorderPatrol SE300B-EXD, a single-ended stereo 300B amp with all of the trappings (hence, the EXD designation).

Turns out that Boss Hull had dropped the word to Mr. Dews that I was interested in playing around with some lower-powered single-ended amplifiers. You can’t say that Gary doesn’t deliver the goods.

The BorderPatrol SE300B-EXD Explained

BorderPatrol offer several different amplifier designs, with multiple options within each variety. The choices can be confusing, but are all really quite nicely outlined over at the brand new BorderPatrol website. This time around we have the BorderPatrol SE300B-EXD, a single-ended amp putting out around eight watts per side. Pretty typical for such an amp, but the devil (as always) is in the finer details.

It’s well known among those in audio circles that Gary Dews is more than just a stickler when it comes to power supplies. How the current is delivered to the output tubes really matters: one manufacturer’s eight watts can be very different from another’s eight watts! We all know that single-ended direct-heated triode amps using such output tubes as the 300B, 2A3, or 45 can sound amazingly immediate, tactile, and lifelike. We also know that such amps can be finicky at best. You know what’s been said: weak, flabby bass; exquisite midrange; but crazy attention required to speaker matching. These are amplifiers that have been characterized as little more than “tone controls” for well-heeled and most likely off-kilter audio enthusiasts. The ones that have gone a tad too far down the rabbit hole while consuming the Kool-Aid.

I’m here to tell you that nothing could be farther from the truth. As single-ended amps become more mainstream, so too are the speakers that match well with them. Maybe I’m just shining more light in that direction, but it seems like efficient speakers boasting easy loads are popping up like mushrooms all over the place.

So then, what makes the BorderPatrol SE300B-EXD different? I’ll paraphrase Gary’s well-written explanation of his design philosophy in the following paragraphs. First off, the importance of the power supply varies somewhat depending on the architecture of the amplifier design. A good power supply is a must for any amplifier but as Gary tells me, a well-designed and executed Class A push-pull amp (like his P21-EXD I reviewed previously), in which one tube pushes whilst the other one pulls, doesn’t need as “stiff” a power supply since the current demands are not as great. Move to a single-ended design where only one tube per channel handles the whole input signal, and the power supply requirements change. Here, a much “stiffer” supply is needed since current swings in the output tube become much more drastic. Remember that the job of the power supply is to provide constant voltage to the output tube in response to the current/power demands of the speaker.

BorderPatrol addresses this issue of “stiffness” by utilizing a choke input filter power supply with a high-current capacity rectifier tube (specifically, the GZ37). As Gary points out, the extra stiffness of this type of power supply allows BorderPatrol single-ended amps to drive a wider variety of speakers to good effect than the typical single-ended amp might handle. The listener gets more punch, better bass definition, and the ability to reproduce much more complex music without the dreaded “wooliness” and collapse of soundstage and dynamic range.

Secondly, the output transformer (OPT) also plays a vital role in music reproduction in that it defines both the low and high frequency bandwidth of the amp. A SET OPT also needs more metal core than a push-pull type to handle the output tube current without saturation. (Remember, the currents in a push-pull OPT cancel whereas the current in a SET OPT does not).

A big metal core with lots of turns of wire is great for the low end but capacitance and inductance effects will roll off the high frequencies. BorderPatrol moves deftly around this issue by using a split-bobbin construction and arranging the wires into 12 primary and 10 secondary sections, minimizing the parasitic inductance and capacitance to give extended high frequencies. This architecture, along with cryo-treating (in the EXD version) works together with the “stiff” power supply to yield an almost ruler-flat bandwidth across the range of human hearing. This, and the ability to provide current when needed.

Tech-talk behind us, let’s move on to listening to the BorderPatrol SE300B-EXD.

BorderPatrol SE300B-EXD Setup

My time with the BorderPatrol SE300B-EXD was experienced with the following system configuration. Digital media were converted and interpreted using either a Bricasti M1 Special Edition DAC (streaming) or a Sparkler Audio S503 “Spiral” disc spinner (CD). Preamplification was supplied by a Linear Tube Audio MicroZOTL headphone amp/preamplifier feeding signal directly into the SE300B-EXD. Speakers used consisted of the Charney Audio Maestro X or my Living Voice IBX-R3 monitors.

Well, how was it?

First off, I reminded myself that the BorderPatrol SE300B-EXD was a single-ended eight watt per channel amp. I wasn’t tempted to try it out with every speaker in the house like I did with the BorderPatrol P21-EXD push-pull amp, which puts out more like 20 robust watts per side.

My very first listen with the BorderPatrol SE300B-EXD was with the Charney Audio Maestro (non “X” version) speakers, which I have since returned to the manufacturer. My initial impression of this matchup was that the BorderPatrol amp gave the deepest, most defined, and warmest bass that I had heard (or ever would hear) from that Maestro. The amp was most certainly off to a great start.

While I found the Charney Maestro to be an excellent speaker, it was never a great fit to my listening environment. Fortunately for me, Charney Audio subsequently loaned me the very first prototype of their new version of the speaker, the Maestro X. This design essentially doubles the depth, and hence, volume, of the original Maestro. The result is
an equally efficient speaker that does some amazing things in my room that the original just couldn’t quite deliver. I subsequently found it to be an almost perfect mate to the BorderPatrol SE300B-EXD amp. Most of my listening notes therefore reflect my experiences with this amp/speaker combination.

What the BorderPatrol SE300B-EXD delivered in combination with the Maestro X was music with real heart and soul. I’m a detail/resolution freak, and yes, that feature was there. However, there was additionally enough warmth enveloping me to convey real emotion and feeling to the notes that I was hearing.

In contrast, I found the push-pull P21-EXD to be exceedingly detailed via the original Charney Maestro, but overall a bit clinical. I didn’t quite get the emotion I really wanted through that pairing. However, when I coupled the P21-EXD to the Living Voice speakers I have on hand, the warmth and feeling came back. Conversely, the single-ended SE300B-EXD gave the best sound I could get using the original Maestros. But coupling it with the Maestro X speakers was next-level altogether; this setup has brought me countless hours of lights-off, late night musical bliss.

Want to hear what the BorderPatrol SE300B-EXD is capable of in the best possible light? Easy! Just pull out your favorite small ensemble jazz recording, turn off the lights (and your phone) and listen. Just listen. It may take your ears some time to adjust and your brain to calm itself, but you’ll get there. I promise.

I remember a day years ago when I was a young teen. It was the end of one of those hot, endless summers of childhood where day after day one could see the heat rising from the ground in great swaths of visible distortion. That day, however, was warm, yet crisp, and oddly bright. There wasn’t a cloud in the sky, and I felt that I could see out to infinity given the clarity of the atmosphere. The late summer leaves were exceptionally bright in color; a most realistic hue. The sun glinting off the water surrounding my house was like tiny dancing diamonds. For some reason, that day stands out in my memory,
and it perfectly represents my feelings about the sound I get from the BorderPatrol SE300B-EXD amp playing through the Charney Maestro X speakers. Almost perfectly real and remarkably clear, but not in an artificial or overdone way. No sense of haziness whatsoever.

All right, so back to small ensemble jazz. A recording I often use to suss out the finer details of any audio component is Force Majeure (24/44.1 Hz flac file, streamed via Qobuz), which was recorded by bassist Dezron Douglas and harpist Brandee Younger in their New York apartment. As such, it’s an intimate recording resplendent with sounds of passing traffic outside and darting children inside. In many cases, we often think of superb gear transporting the musicians into our listening rooms; here, the opposite happens: we are transported into their living room. The BorderPatrol SE300B-EXD plays this little sleight of hand better than any other amp I’ve auditioned.

Besides the expected clarity and “lifting of veils,” I experienced unprecedented “snap and pop” from Douglas’ plucked bass coupled with the complex harmonic structure of Younger’s acoustic strumming. Isolated spatial details such as finger snaps were sharp and exceedingly well defined in the naturally portrayed soundstage of the recording. Speaking of images, the bass and harp were precisely placed in three-dimensional space; however, there was also a satisfying fullness to the scale of each instrument. From cut to cut, it was easy for me to identify how the two musicians moved about the room relative to one another, as well as to the microphone placement.

Listening with the Living Voice IBX-R3 speakers

I recall Gary Dews telling me that many of his amplifier designs were voiced using Living Voice multi-driver speakers like my IBX-R3 model. In fact, I bought these speakers on Gary’s recommendation seeing as I was getting involved with more and
more of these low-powered vacuum tube amps. While the LV speakers look like normal narrow-profile towers, they have the advantage of being quite efficient and easy to drive. Besides, Scot Hull has a similar pair of LV speakers and readily endorses them.

Did they acquit themselves well with the BorderPatrol SE300B-EXD? In short, yes.

First off, the sound was somewhat different from what I’d come to expect with the single-driver Charney Maestro X. What I heard was something more mellow and laid back; not quite as “in your face,” if you catch my drift. To elaborate, let me bring you back to a more recent memory of mine that also involves a somewhat memorable day. This one happened just a few years back, when I was cycling on a local trail in late April right after an afternoon rain shower. The temperature was comfortably warm, but the after effects of the rain still hung in the air. I recall mist rising from the ground, a thickness to the air, and incredible intensity of smell and tactile sensation of the air moving past me. I could fully sense the presence of the atmosphere around me, and the aromas of fresh honeysuckle and organic earth enveloped me. The experience was intoxicating, and I didn’t want it to end.

Thus it was with the BorderPatrol SE300B-EXD driving the IBX-R3 speakers. The sound was similarly intoxicating in a vividly and sensually dense way. Bass and midrange had a uniquely tactile texture and complexity that I’ve rarely experienced in recorded music. Treble seemed a bit softer and more distant than I heard with the Charney speakers, but nonetheless present. I’d rate the overall sound as being almost otherworldly vivid, or better yet, magisterial. This combo had real presence. The visual equivalent, if I didn’t make myself clear enough with my rainy day analogy above, would be viewing a Maxfield Parrish painting.

The trade-off (yes, there’s always a trade-off) was a slight loss of resolution and immediacy that I heard with the single-driver Charney speakers. I sometimes found myself turning up the volume or listening a bit more intently to catch details in the music that I knew were there, but that just weren’t coming through.

But, dear friends, it’s all just horses for courses, or whatever the saying is. I had no trouble turning off the lights, planting myself in my chair, and listening to Jan Lundgren’s new album Into the Night (24/44.1 kHz flac, streamed via Qobuz) three times through, well, into the night. And I enjoyed every second of it, just in case you are curious.

So? Are you SET curious?

If you are one of those fortunate souls in the market for a no-compromise single-ended 300B amplifier, should you consider the BorderPatrol SE300B-EXD? Damn right you should!

Summing up, you get a copper and wood clad amplifier, overbuilt power supply, artisanal build quality, and great application of modern technology. Gary Dews has really thought this thing out, and he’s gone to tremendous lengths to get the most goody out of the classic 300B tube in the single-ended configuration possible.

No, $13,500 isn’t cheap, even in the overinflated world of high-end perfectionist audio. You’d still do well to shop around at this price point, paying special attention to speaker matching. As I hope to have pointed out, I thought the BorderPatrol SE300B-EXD was swimmingly good with the very efficient single-driver speakers I used with it. But the Living Voice IBX-R3 speakers? Well, if I had to opt for one or the other, I’d probably go with Gary’s more powerful push-pull P21-EXD amplifier. The extra power was nice with these less efficient speakers, and that amp’s more detailed and slightly cooler presentation seemed a bit of a better match with the more reticent and warmer Living Voice speakers. Well, at least to my ears…

That said, the BorderPatrol SE300B-EXD is a real honey of an amp. It is therefore eminently deserving of a PTA Reviewer’s Choice Award. So, congratulations again to Gary Dews and BorderPatrol Audio. This reviewer trusts (nay, expects!) that they will keep up the excellent work for years to come.