In Playback 41 I reviewed the terrific Burson Audio HA-160 headphone amplifier (click here to read the review), finding it to be “a superb sounding and incredibly well made headphone amplifier that is more than reasonably priced at $695.” But one point I mentioned only in passing in the review is that I often listened to the HA-160 headphone amp with another important piece of Burson gear inserted in the signal path; namely, the firm’s AB-160 RCA audio buffer stage ($549). Frankly, Burson’s audio buffer and headphone amp fit together like hand and glove, together creating an overall sound that is greater than the sum of the parts. This, of course, raises two important questions: what exactly is an “audio buffer stage” and why would listeners want to use one? Let me try to provide a brief explanation.
Burson Audio contends that one of the main reasons why audio systems sometimes fail to live up to our expectations is that there are impedance mismatches between the output stages of our chosen source components and the input stages of our preferred amplifiers. The result of these mismatches, says Burson, is both “signal loss and distortion,” most often perceived as a loss of low-level sonic detail and an apparent blunting or dulling of transient sounds—as if some of the expected life and vividness of the music has been drained away. In simple terms, Burson’s audio buffer can be thought of as a figurative “black box” whose purpose is to “remove any impedance mismatch by acting as an isolation platform between any of the source components … and downstream amplification.”
Let’s speak candidly. The whole idea of adding a buffer stage to improve system performance seems to run contrary to the established beliefs of audio purists whose working assumption is that simpler and less cluttered signal paths always sound better than complex ones. In short, many purists would argue that it is simply a fool’s quest to try to realize sonic gains by adding more circuitry to the system—in this case the circuitry found in the AB-160 audio buffer. Even so, Burson’s fundamental claim is an interesting one, since their point is that source components can only give of their best when presented with optimal and easy loads to drive (otherwise, all sonic bets are off).
The AB-160 provides what Burson terms a “high sensitivity input buffer (HSIB)” which is a very high impedance (and thus high-sensitivity) FET-based input stage that is extremely easy to drive and that, Burson claims, “effectively allows our buffer stage to match up to any input or output signal drains.” The AB-160 also provides a modest 3 – 6 dB of gain, thus making good on Burson’s promise that its audio buffer “will increase signal transmission efficiency between all components, unlocking the potential of any system.” As you’ll learn in this review, these statements on Burson’s part are not mere hollow marketing claims; they’re actually a pretty accurate synopsis of what the AB-160 is and does.
For a really in-depth discussion of the technologies used in the Burson AB-160 (and the design philosophies behind them), you’ll want to visit the Burson web site: www.bursonaudio.com. Here, though, I’ll provide just a few highlight that listeners will want to know about.
•Dual mono circuit design with extremely short (“less than 6 cm” or 2.36”) signal paths.
•Features high sensitivity input buffer (HSIB), which is a very high impedance, high-sensitivity, FET-based input stage that is extremely easy to drive. The circuit is fully balanced and operates in pure class A mode.
•In keeping with Burson tradition, no integrated circuits (ICs) are used anywhere in the AB-160, since Burson passionately believes that ICs sound inferior to discrete high-quality semiconductor devices.
•Low noise, regulated power supply featuring, again, discrete (not IC-based) regulator devices.
•Resonance free aluminum (RFA) enclosure is precision milled from 6mm slabs of aluminum. By design, the case panels each have different resonant frequencies and together form a rigid enclosure that doubles as the heat-sink for the AB-160. The entire component offers exquisite, camera-like fit and finish (though the AB-160 is far more physically robust than any modern-era camera we have seen).
•High quality parts and construction methods are used throughout, including a “high quality PCB” and “Elna Audio graded caps, carefully matched high quality audio transistors, DALE military graded resistors ...” All components are hand-soldered.
•Wide bandwidth design: Burson quotes a frequency response specification of 0 – 220kHz (-3dB).
•Low noise design: Burson quotes a signal-to-noise ratio of -120 dB.
•Dual, switch selectable inputs (RCA version).
For our listening tests, I set up a test system that could be configured in two ways. As a constant, I used a very high quality Musical Fidelity kW SACD player as my primary source component, with the player either driving:
•The Burson HA-160 headphone amplifier directly, or
•The Burson AB-160 audio buffer, which in turn drove the Burson HA-160 headphone amplifier.
Primary listening was done through a pair of HiFiMAN HE-6 planar magnetic heaphones (click here for the review).
Additional tests were conducted using an analog front end consisting of a Nottingham Analogue Systems Space 294 turntable/Ace Space 294 tonearm, Shelter 901 MkII phono cartridge, and Fosgate Signature phonostage. The system was also used with an iPod Classic and HRT iStreamer DAC. Additional headphones used in listening tests included the Audeze LCD-2, HiFiMAN HE-5LE, Shure SRH840, and Ultimate Ears In-Ear Reference Monitors.
Here’s where things get interesting. Frankly, I came upon this review with no small measure of skepticism, and for two reasons. First, the Musical Fidelity player had already sounded superb through the Burson HA-160 headphone amplifier. Second, long experience had shown me that the robust output stage of the Musical Fidelity player had typically been able to drive the inputs of a wide variety of amplifier—almost always with great results. In short, it was difficult for me to picture ways in which adding the AB-160 audio buffer would somehow “make things sound better.” And yet it did, and in two key ways.
Better resolution for low-level details
As I listened very carefully to track after track, there was no denying it; Burson’s AB-160 offered significant improvements in resolution of low-level textural details in the music. In one sense, the improvements were small and subtle (as you might expect, given the already very high quality of the source component in use). But in another sense, the improvements were very significant, in that they unlocked a whole additional layer of resolution and sonic finesse that had been missing before. Echoes, reverberation “tails,” ambient soundstage cues, and subtle variations in timbre and inflection suddenly became clearer and more complete, so that the overall sense was of stepping up from one grade of component to the next higher level (or two).
Superior rendering of transient and dynamic details
One improvement I did not foresee but that quickly became apparent on some tracks was the AB-160’s ability to unlock sharper, clearer, and more incisive reproduction of fast-rising transient sounds and dynamic swells. Frankly, I might not have noted anything “wrong” with the sound of the system without the AB-160, but once it was brought into play I found that the leading edges of transient sounds seemed more crisply rendered (yet without apparent overshoot), so that I could at once hear and feel the launch of individual notes and sounds. Momentary variations in dynamic emphasis and expression were clearer and had greater impact, too, so that the energy driving musical performances became more explicit and visceral. Together, these improvements joined forces to convey the sheer life of the music more effectively—sometimes in surprisingly dramatic ways.
The Big Picture
I can see how some listeners might feel that the overall magnitude of changes/improvements offered by the AB-160 is relatively small, and thus question the product’s value or cost-effectiveness. But, if you start out with old audiophile’s admonition that the final five percent is the hardest (and typically the most expensive) part of the sonic equation to get right, then the AB-160 starts to make perfect sense.
Here’s the math. If you owned a Burson HA-160 headphone amplifier ($695) you would enjoy very high quality sound and one of the best deals going in the high-end headphone amp marketplace. But if you then added the Burson AB-160 audio buffer ($549), you would find the overall sound of the electronics package improved—yes, in subtle yet also musically significant ways—to a point where the Burson pair began to rival the sonic qualities of headphone amplifiers priced at $2000 or more. Pretty cool, no?
On the track “Kicho” from Blue Chamber Quartet’s First Impressions [Stockfisch SACD], the bowed acoustic bass solo that opens the song becomes much better defined, so that you can hear the interaction of the bow on the string—especially on the spectacular, low-plunging not that draws the introduction of the song to a close. Later, note the sheer vigor of Julia Bartha’s piano lines, where—with the AB-160 in play—some notes and phrases have almost explosive dynamics that are very difficult to reproduce. Finally, listen to Angelika Siman’s harp phrases, which at times double or augment piano lines. Through some electronics it can be difficult to separate the sound of the harp from the piano, but with the AB-160 in the signal path the instruments are always beautifully delineated.
In the title track for Mary-Chapin Carpenter’s Come On, Come On [Columbia], note the way in which the AB-160 opens up the apparent size of the soundstage but letting you hear previously obscured low-level ambient and reverberant cues. This is the sort of track that sounds nominally good through most equipment, but that it capable of a much higher level (better than merely “good”) of sound quality—a level the AB-160 helps to unleash. But, where the AB-160 gives you more of the good stuff in fine recordings, it can also make occasional problems and glitches more apparent. With the AB-160 in play, for instance, there are moments where it sounds as if Ms. Carpenter’s voice has been “rinsed” through a studio dynamics processor whose effects, as it turns out, are not always beneficial (the AB-160 helps to reveal moments where vocal swells sound just slightly “over the top”).
Listen to the classic jazz piece “Take Five” from The Dave Brubeck Quartet’s Time Out [Columbia SACD] and note the inner details of Paul Desmond’s lovely sax solo. Very subtle mouthpiece and reed noises, which many amplifiers either suppress or only partially reproduce, remain subdued and yet become crystal clear and explicit with the AB-160 in the signal chain, so that overall realism takes a significant jump upward. But even greater sonic benefits accrue as you listen to Joe Morello’s brilliant drum solo in 5/4 time. When the AB-160 is brought into play literally everything about the sound of Morello’s drum kit gets better. The attack, sustain, shimmer, and decay of the cymbals, for example, sounds markedly more complete and authentic—not compressed or truncated as with some amplifiers. Similar, snare drum shots and kick drum accents have real transient speed and energy (much like the real thing) once the audio buffer is used, whereas they sound like rather pale imitations of themselves if the buffer is removed. This tracks shows how the AB-160 helps to reveal the true shape of the dynamic envelopes of each note, so that you can fully appreciate it when artists like Morello demonstrate their masterful control of dynamics.
Finally, check out the Michael Tilson Thomas/Paul Jacobs/San Francisco Symphony performance of the first (Prelude Andante) movement of Aaron Copland’s Organ Symphony [SFS Media, SACD]. In particular, pay very close attention to the voice of the pipe organ, itself. With the AB-160 installed, bass pitch definition improves, so that you can fully appreciate the subtle voicing differences between the various registers of the organ and can, on very low notes, hear how the organ activates the entire hall with waves of bass energy. With the audio buffer in play, the organ continues to sound powerful (as it almost always does), while taking on a heightened measure of subtlety and delicacy that greatly enriches the listening experience.
Consider this audio buffer if: you would enjoy a product that, in simple terms, makes good components sound even better. While the magnitude of the improvements wrought by the audio buffer may be relatively small, the collective impact of the sonic changes is not—especially for those who are chasing that elusive top five percent of improvement.
Look further if: you feel you might be ahead of the game to step up to higher level core components rather than investing in a “helper component” such as the AB-160. But weigh costs and benefits carefully; you may find the AB-160 gives precisely the kinds of improvements that matter most to audiophiles, and for a reasonable price.
The Burson Audio AB-160 is a well conceived and well made add-on product that, exactly as advertised, unlocks higher levels of inner detail, transient clarity, and dynamic expression. For those who care about the fine points of sound reproduction, the AB-160 will be a worthwhile investment.
SPECS & PRICING
Burson Audio AB-160 audio buffer.
Inputs: two stereo analog (single-ended, via RCA jacks)
Outputs: one stereo analog (single-ended, via RCA jack)
Frequency Response: 0 - 220kHz (-3dB)
Gain: 3 – 6 dB (selectable)
Signal/Noise: -120 dB
Output Noise Level: 0.015 mV
Dimensions (H x W x D): 3.15” x 7.09” x 9.84”
Weight: 12.125 lbs.
Price: $549 (RCA version), $599 (XLR version)