Spent a few minutes with the AKG-1000 air speakers (now
discontinued) being fed some familiar Diana Krall and Dave Grusin tracks. They
were driven by an AMB ß-22 headphone/speaker amplifier by AMB
Laboratories. In fact, AMB had quite an extensive line on display, each
powered up to show attractive blue LED lighting under clear top plates. The
one-tubed unit placed the LEDs underneath the glass envelopes, causing the
whole tube to glow (but barely visible in my flash photo). My listening notes
from my AKG-1000 listen read "bass is there, not prominent. Midrange a bit
light. Outside-the-head quality is there from midrange on up -- piano,
percussion, and bells, for example." Switching to the HD650, I found "the
sound is dry, with clinical treble. Bass transients are sharply delineated,
perhaps unnaturally so." Well, it is just a brief show audition, so please
listen for yourself.
The HeadAmp booth impressed me
more. I listened to the GS-X
Dual Mono Headphone Amp/Preamp, which is a 2 chassis unit. Build
quality was quite professional and cosmetics clean and no-nonsense. I was
pleased to find it was a balanced design, yet with single-ended outputs as
well. I was thus able to compare my HD650 with another just like it but wired
in balanced mode with XLR connectors. I found balanced mode made a world of
difference – voices had space and dimensionality, and instruments sounded
even more believable. Bass sounded like a real instrument, not just a low
frequency signal. Treble was a bit more defined and realistically, lead vocal
floated in a space of its own like a good speaker setup, and backing vocals
spread across the stage, allowing each to be singled out. I tried my familiar
Harry James remaster by Sheffield Labs next. The balanced output was more
palpable, full of life, more believable as a big band. Switching back to the
unbalanced phones indicated that, to the analytical mind, the difference is
not objectively large; but to the music lover it was instantly apparent and
addictive. This, plus a recent audition of the Headroom Home Max Balanced, convince me that, at least
for solid state, balanced is the way to go. Speaking of balance, I didn't
see a balance control on the GS-X, but it did have a three-position gain
switch. The
source feeding the GS-X was an Original CD-2008
Mk-II.
As Tyll
described the benefits of balanced headphone amp designs, there are at
least four advantages. One is it eliminates the common ground wire tying the
two drivers together. A separate amp drives each side of each driver,
identical and without any tie to ground. Second, the distortion of each amp is
cancelled by its mirror-image amp, at least those distortion products that are
symmetric. No amp is free of audible distortion, even if it can only be
detected indirectly as "texture" (grainy, glassy, ceramic, edgy, bright),
even though measurements suggest they should be inaudible. Third, using two
amps in push-pull doubles the slew rate. One drawback is that each amp only "sees" half the voice coil impedance, and thus is driving a lower
impedance, more difficult of a design challenge. A balanced design also
doubles the parts count, and requires testing and matching components so that
distortions are indeed equal and thus cancelled.
As I walked to tables closer to the middle of the room, I found unattended
setups that I suspected might have been brought by hobbyists and collectors,
not necessarily from manufacturers. I took a listen to Rebecca
Pidgeon on a Linn Ikemi HDCD player, feeding a Zana Deux
tube headphone amplifier. This amp ran very hot, particularly near the two
output tubes -- too hot to touch. It sports a selector for three inputs, and a
total of 5 tubes including 2 large output tubes, alas without markings. The
sound into my HD650 (unbalanced, darn) was a bit light on top. Rebecca's
voice seemed even lighter than usual. Piano didn't have the body and lower
midrange power I'd expect. I then switched to a nearby Audio
Technica ATH-W1000Sovereign. Ah, this was much more detailed,
crisp, with a clearer voice, but still a touch bright, a touch too much treble
energy. Midrange was more fleshed out, however, closer to the robust Grado
sound, but not that exaggerated. Here was a realistic sounding piano. Treble
air, definition, and distortion were all very good. A little midrange hardness
was heard with all headphones tried on this setup when the voice got loud; not
sure if that was from the recording or electronics.
Switching again, I tried the Grado RS-1. I noticed distinct
sibilance, and a less-defined treble. There was a bit too much chest to her
voice, not what I consider realistic based on hearing this disc at home on my Vandersteen
3A Signatures. Piano was believable, but these cans were not nearly as
clean in the treble as the Audio Technica. Next, I donned a borrowed pair
(thanks!) of Audio-Technica ATH-L3000, Leather by Connolly. Treble
became more natural, not as tipped up. Instruments were believable.
Rebecca's voice was more continuous from its fundamental through high
overtones, and far more appealing. The piano was fuller, more round, had more
body, but was a bit dark. Midrange was more full. Jumping back to the HD650, I
confirmed that the treble far less resolving and detailed. Relaxed, not
seeming artificial, but not believable. Voice faired a bit better. Treble was
there when you needed it, not bright and persistent. Overall, the HD650
sounded a bit muddy and vague, but pleasingly soft. Next up, the AKG
K701 was a bit similar to the HD650, but a more airy treble, and less
dark in the midrange, a bit more forward. Treble distortion seemed higher, a
bit shimmery and splashy, as if less controlled. This I felt I could not live
with on a daily basis.
Next came the Audio-Technia ATH-W5000
Raffinato, one that is actually still in production. This didn't
line up well or seal on my head! Probably operator error. An Agfa two-track reel to reel was driving a Zana
Deux.
High-Performance Audio Reviews
