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equipment
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Air-Tight 211 SET Monoblock Amplifiers
Scot Markwell
Sometimes, amplifiers with
simple circuits manage to
capture more of the essence
of music than those with
more complex ones; the Air-
Tight 211 single-ended triode (SET)
monoblock is such an amp. It belongs in
the top echelon of the SET amplifiers I’ve
heard in the four years or so of I’ve been
researching and listening to the breed.
The Air-Tight amplifiers came to me
while I was auditioning several other SET
designs, along with a few high-sensitivity
speaker systems, so I was able to compare
them to other amps of similar power
and price, as well as lower and higherpowered
designs. More importantly, having
several compatible speaker systems
around gave me the chance to hear how
these amplifiers reacted to differing loads.
I want to stress right upfront that anyone
interested in seriously pursuing SET
amplifiers, whether an inexpensive
design or a more upscale set such as the
211s, needs to accept the fact that these
are special amplifiers that require careful
loudspeaker matching. Remember that a
sensitive speaker can be easily driven by
almost any amplifier, but a SET, with
very rare exception, must be partnered
with a high-sensitivity loudspeaker to
play music at natural levels without gross
distortion and compression of the signal.
Despite what some marketing types may
tell you, what is really necessary for SET
amplifiers up to about 30 watts per channel
are speakers with a sensitivity of at
least 92dB/watt and an impedance curve
that does not dip below 6-8 ohms, especially
in the bass.
Because of these limitations, a lot of
audio folks have declared SET designs
obsolete, but the truth is that restrictive
loudspeaker matching is neither a bad
thing nor an encumbrance. If one wants
to enjoy the many sonic benefits,
charms, and sexiness of SET amps, then
there is only one way to go with speakers—and
this is just the way it is.
It used to be, even a few years ago,
that some of the speakers that functioned
best electrically with these amps
were among the worst sonically. But
today things are much better. The quality
of SET sound I’ve heard with speakers
like the Reference 3A Royal
Virtuosos or the Living Voice Avatar
OBXs that I now use—or the Horning
Alkibiades Signature Golds, Coincident
Total Eclipses, or Lamhorn 1.8s I’ve used
in the past—can be superb, on a par
with the many conventional loudspeakers
that must be used with higher-powered
amplifiers. While none of these
high-sensitivity speakers was or is perfect,
all were superior communicators of
music with low coloration; all sounded
life-like enough to make me want to
keep listening for extended periods,
without fatigue or dissatisfaction.
With appropriate system matching,
the Air Tight 211s offer a level of performance
that easily makes one forget
about the laws of physics and just relax
and listen to music. The basic character of
the 211s entails a fully-developed dimensionality
and a tonal balance that, though
warm and inviting, is refreshingly free of
many of the “traditional” SET deviations
from neutrality that mar many of even
the most revered designs. Virtually
unique in my experience of SETs is the 3-
D quality these amplifiers exhibit, especially
with LPs. With the best recordings,
the 211s develop a soundstage depth and
lateral spread that ranks with the top two
or three SETs I’ve heard—indeed, with
the best amplifiers I’ve heard.
Along with this soundstage prowess
comes an ability that I have not heard
elsewhere to such dramatic effect, one
that is riveting both musically and sonically:
When presented with high-fre-
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quency transient information such as
cymbal crashes or synthesizer chords,
like the big “splashes” of cymbal-like
information on Frankie Goes to
Hollywood’s Relax (Island UK, 45rpm
LP), this amplifier projects a huge,
almost enveloping cloud of intense
high-frequency “mist.” The effect is
akin to being in near proximity to a
steam valve on a big boiler as it lets off
pressure; it is as if a big wall of steamhiss
suddenly appears, larger-than-life,
before your eyes and ears, and then fades
away with no carry-over or heaviness—
just a massive jolt of high-frequency
information that suggests space and
three-dimensional volume and extended
treble response. Synthesizer tones and
effects are, of course, hard to describe,
but I can’t help feeling that what I was
hearing was what the record producer
intended me to hear.
Such performance at the upper end of
the frequency spectrum would be worthless
if the midband and bass were not as
well served. Happily they are. As a matter
of fact, the midrange and bass of the
Air Tight 211s form a sonic cloth cut
from the same seamless bolt as the highs.
Many times the excellent midrange performance
of SET amps comes at the cost
of extension at the frequency extremes,
and what performance they do have at
either end is usually colored and typically
a bit sloppy and ill-defined. The 211
is different in that, with any of the speakers
I tried, both the bass and treble
remained solid and reasonably flatsounding
and well-integrated into the
overall presentation. No band of frequencies
really stands out from the others,
with the exception of the extreme highs,
where occasionally really high overtones
can sound slightly exaggerated or spotlit.
So sweet and low in distortion is the
upper-octave response of the 211s, however,
that I never felt this to be a problem.
On the contrary, I was more struck
by a sense of openness and unfettered
dynamic and dimensional response. If I
had to choose, I would much rather hear
highs reproduced with such smoothness
and vigor than to hear them rolled off or
dynamically deadened.
These amplifiers have the punch to
back up their dynamic authority. Rated
at twenty-two watts of Class-A power
per monoblock, the 211s are near the
upper limit of what can normally be
done with a single output tube in a
Class-A SET design. Of the amps I had
on hand for this review, their only real
competitors were the Vaic VV 52B
stereo integrated amp at 30 watts per
side and the Ayon 32B Classic
monoblocs at 20, but that is a negligible
78 THE ABSOLUTE SOUND ■ AUGUST/SEPTEMBER 2003

equipment
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power difference and in practice virtually
impossible to hear in terms of output
level at the loudspeaker. The Vaic, at
approximately the same price, exhibited
a slightly weightier and powerful
extreme bottom end and a similarly
extended treble, but did not have the
refinement and seductive sweetness of
the 211s. The Ayon amps were actually
quite similar, although slightly leanersounding
in the midbass than the 211s.
Big, big records like The Human
League’s Don’t You Want Me Baby
(Virgin UK, 45pm LP) or David Bowie’s
“Theme from Cat People” (Putting out
Fire [Backstreet 45rpm LP]) feature
awesome, powerfully deep, and loudly
recorded bass notes on drums and synthesizers
that can terrorize most SET
amps. But with either the 3A Royal
Virtuosos or the Living Voice Avatar
OBXs, the Air Tight amps just sailed
through the peaks and delivered the
goods. The last half of the bottom octave
seemed to be somewhat rolled off, but I
imagine that could be addressed with
speaker placement closer to the rear
wall. That is a setup I preferred not to
use, as I am biased towards the depth
and dimensionality I get with placement
well out into the room—in my case
about three to four feet out.
I found I could listen without strain
to well over 100dB peaks in my goodsized
room (approx. 18’ x 10’ x 8’ with
lots of damping) and not hear any hint of
compression or strain right up to the
211s’ considerable power limit. Digital
fare like the Gladiator soundtrack on CD
[Decca/Universal], or perhaps the Glory
soundtrack on Classic Record’s 96/24
DAD, definitely pushed the 211s to that
limit when played loudly, but the sonic
picture remained coherent right up to
the point of clipping. Unlike many
higher-powered tubed amplifier designs,
where the onset of clipping is usually
heard as a general distortion and raggededge
to the sound that can be reduced by
just dropping the volume a bit, hard
clipping on an SET amp is most often
characterized by an abrupt blatting
noise in the bass and an acutely uncomfortable
out-of-control sound in the
midrange, especially on vocals. This is
not to say that the Air Tight 211s react
any differently that other SETs when
pushed past their limits, only to note
that these limits are reasonably high
with the right speakers.
When matched with such speakers,
the 211s are magical in the best tradition
of SETs. Sweet, grainless, and
blessed with both the creamy, emotionally
expressive, and slightly projected
midrange of better SET designs, as well
as relatively potent bass and dynamic
authority, the Air Tights make a strong
case for their kind. With the $4000/pair
3A Royal Virtuosos, the 211s have truly
wide dynamics and superb high-frequency
extension, with a fully-fleshed
midrange that lends a sense of listening
with no “roof” on the sonic proceedings.
Although bass information is well-rendered,
the amplifiers are taxed when
asked to reproduce gargantuan organpedal
notes and deep synthesizer rumblings.
But the six-to-eight ohm, directdrive,
crossover-less mid/woofer of the
3A presents the 211s with a super-easy
load to drive (no heat or power wasted
battling a crossover network). The onpaper
higher-sensitivity (94dB/watt)
$7000/pair Living Voice Avatar OBX
have a balance somewhat similar to the
3As, but tend towards a slightly leaner
and less voluptuous sound, albeit one
with slightly greater bass extension.
I also tried the 211s with the new
$4000/pair Alón Lotus Elite speakers, a
design that has evolved from the original
Lotus of a few years ago (a speaker of
about 90dB/watt and with a 14-ohm
woofer designed specifically for SET
amps) to a dual-woofer, more conventional
three-way speaker, designed optimally
for a bit more power than that 211
has. However, played within their limits,
the Air Tight amps displayed a
remarkable affinity for the Alóns, making
a bigger and slightly warmer sound
than they did with the other two speakers,
with truly remarkable bass authority
and extension. The Alóns were, in
many respects, the best match for the
211s, but their more complicated
crossover and lower sensitivity (around
89dB/watt) necessitated tighter control
of the volume knob.
I have thoroughly enjoyed my time
with the Air Tight 211 amplifiers. The
$9995/pair 211s have more than enough
juice to drive sensibly-chosen speakers
and, while by no means inexpensive, are
not overpriced for the sound they deliver.
Their refined, smooth, extended, dimensional,
and dynamically authoritative
presentation make them a very attractive
choice for someone looking to assemble a
superior SET-based system that will not
suffer from most of the limitations of the
Air Tight’s lower-powered brethren. &
SPECIFICATIONS
Power output: 22 watts Class A
Dimensions: 15.3" x 10.3" x 14"
Weight: 55 lbs.
ASSOCIATED EQUIPMENT
VPI HW-19 MK IV turntable w/VPI JMW
Memorial 10.5 arm; VPI Aries Scout
turntable w/VPI JMW 9 Memorial arm; Benz
LP, Clearaudio Harmony Wood, Clearaudio
Insider Reference Wood, and Madrigal
Carnegie 1 MC cartridges; Plinius M-14 MC
(solid state) phono section and Hagerman
Technologies (tubed) MM phono section with
VAC step-up transformer; Plinius M-16 (solidstate)
and Emotive Audio Sira (tubed) line
stages; Viva 300B, Vaic VV 52B, and Ayon
32B Classic SET amplifiers; ART Audio Opus
X push-pull tubed monoblock amplifiers; Cary
Rocket 88 triode/push-pull tubed amp,
Forsell Air-Bearing CD Transport and EAD
Theatermaster DAC; Reference 3A Royal
Virtuoso, Living Voice Avatar OBX, and CAS
SM-50 loudspeakers; SLM/Janis subwoofer
with VBT subwoofer amplifier; Alón
Thunderbolt subwoofer; Siltech Gen III, Audio
Magic, and Stealth Technologies interconnects
and loudspeaker cabling, Arcic
Suspense Rack.
DISTRIBUTOR INFORMATION
Axiss Distribution, Inc.
17800 South Main Street, suite 109
Gardena, California 90248
(310) 329-0187
www.axiss-usa.com
Price: $9995/pair
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