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.