- Less is More
the Beauty of Single-Ended 2A3 Amps
first experience with live music was back in '68, when my father, a
carpenter at the Vienna State Opera, took me to a performance of
Mozart's Magic Flute. Little did I realise the lifetime impact that
evening would have.
riveting to sit in the grand hall, feeling the texture and nuance of
each note. I'd never had as much fun or involvement in music before -
I was hooked. But how to achieve that same magic at home?
first pay-checks went towards a Marantz 2235B receiver, an Onkyo
direct drive turntable, a Kenwood cassette recorder and a pair of
Braun loudspeakers; in the decades that followed, many audio products
(medium- to higher-priced gear) became part of the quest for musical
pleasure as close as possible to live.
there was always something missing when listening to vinyl at home.
My system's front end was high quality, a suspensionless
granite-based turntable equipped with a Helius Cyalene tone arm and
Denon DL-103 mc cartridge (which bettered my Linn LP12, Ekos, Lingo,
AT-OC30 mc combination by an audible margin) but music played through
the system lacked emotion and drama - flesh and blood, if you will -
in comparison to a good acoustic live performance. My gut feeling
said it could get better.
those years, I mainly used transistor-based power amplification
(such as Audio Research, Bryston and Krell) which the speakers' low
efficiency required (TDL 3-way transmission line speakers with 85dB
sensitivity). Preamplification was tube-based (Audio Note pre amp kit
with choke and tube rectification, high quality Audio Note paper in
oil capacitors with ECC83 tubes in the phono stage and ECC82 in the
line stage as well as a wonderful German tube line/phono stage based
on ECC83s from Mr. Mollenhauer) which helped improve the system's
sound quality. It also awakened my interest in tube gear.
scoured for information on tube power amplification, and especially
appreciated the late great Harvey Gizmo Rosenberg's inspiring home
page. His love for single-ended triode (SET) amplifiers was
legendary, and the so-called "Triode Guild Master" inspired
others to explore the magic of SET amps, 300B and 2A3 amps in
particular. The stories I read about the latter of these triode power
tubes, rated to provide 3 to 3.5 watts, enthralled me like a glass of
single malt on a cold winter's night. Although you need
"efficient" speakers with a sensitivity of about 91dB or
greater (combined with an impedance behaviour over the audio band
that comes as close as possible to a pure resistor, possibly above 8
ohm, to ensure that the high output impedance of single-ended designs
doesn't modulate the frequency response through the impedance
response of the speaker) it was clear a 2A3 SET amp was the way to go.
a brief technical note: differing from push-pull designs where the
crossover distortion increases with decreasing acoustic level,
single-ended designs have distortion behaviour similar to the
acoustic medium (the air!) which means distortion smoothly decreases
as the acoustic level decreases, resulting in a more natural and
musical presentation to our ears.
to my beloved father, the speakers on hand were close to the 92dB
range (a vintage pair of Altec Lansing Model 15, rated between 90 and
91dB and an easy load to drive) and sensitive enough to give the
project a try (+100dB horns would have been the ultimate partners, of course).
came choosing among the variety of affordable and great sounding 2A3
amps on the market, such as Wright Sound WPA 3.5 monoblocks and
Antique Sound Labs' Tulip stereo amp. For the extra thrill, not to
mention savings, of assembling one's own amp, some are also available
in kit versions: Sun Audio 2A3 stereo amp, and Welborne Labs Moondog
monoblocks (now replaced by a new design), for example. These amps
will set you back $1,400 to $2,800 depending on the quality of parts
and 2A3 tubes ordered. There's a big advantage to 300B SET amps
though, because an excellent pair of 2A3 triodes, like the new
production Sovtek 2A3, runs under $80 for a matched pair - good news
if you know what a 300B triode can cost. There's also the rumour
among SET amp aficionados, that it's hard to design a bad sounding
single-ended 2A3 amp.
much deliberation, I chose the kit-version Welborne Labs Moondog 2A3
monoblocks and never looked back.
what's the sound of a good 2A3 SET amplifier?
to the right speakers, even a low-powered SET amp delivers
unbelievable bass performance. Of course my Altec Model 15 and
Moondogs don't rock the house, but at moderate listening levels they
produce a well-defined, dynamic and powerful bass that's hard to
beat. The soundstage is huge and instruments authentic - music fills
the room with big sound. The mids are the sunny side of 2A3
single-ended triode amps. Smooth and creamy, human voices shine and
if the recorded performance captured it, 2A3 amps deliver the emotion
and drama that define a music lover's Mecca. Take "Amazing
Grace" from Joan Baez's live album From Every Stage (A&M
SP6506) - the recording quality isn't first rate, but the sheer magic
between Joan and her audience is delivered with such beauty that when
the enraptured audience sings the last verse alone towards the song's
end, it never fails to give me goose bumps.
top end is another strength of a good 2A3 amp: clean and sweet,
extremely detailed and absolutely grainless. A good example is how
violins are reproduced in an extremely natural way. Rossini's String
Sonatas for instance, performed by Sir Neville Marriner and the
Academy of St. Martin in the Fields (ARGO ZRG 506), have beautiful
and sweet string tone but also the same tendency to harshness in the
extreme highs you're accustomed to when listening to live violin
music. Another strength becomes visible with the colour of
instruments; Joaquin Rodrigo's Fantasia para un gentilhombre,
performed by Angel Romero & the LSO under André Previn
(EMI ASD 3415), for example, delivers a full palette of classical
instruments (guitar, strings, woodwind and brass instruments)
delightfully and accurately presented by these triode beauties.
up, the overall performance of 2A3 SET amps is awesome over the
whole audio band, with no audible weaknesses. You're invited, if not
compelled, to play music over and over with these low-powered SET
amps because they're so fluid and realistic. My evening listening
sessions often last much longer than planned; I get lost in music
until the early hours.
only downside is the reduced variety of appropriate speakers on the
market. Besides horn systems, and most of them are quite expensive,
there are only a few companies (Loth-X and Triangle, for example)
offering highly sensitive speakers with the moderate impedance
behaviour needed to enjoy the beauty of 2A3 SET amps.
movement on the loudspeaker-builder scene here in Austria. David
Haigner, a young engineer and acoustic expert, designs and builds
made-to-order speakers especially designated for use with low-powered
SET amps. I tried one pair (92dB sensitivity) with my Moondogs, and
the results have been superb; in the meantime I bought a pair of
these awesome speakers for myself (but that's another story...).
next frontier for talented designers should be horn systems (and I
can tell you that David Haigner has detected his love for such
systems... more to come); with the technical knowledge and high tech
materials available these days, the improvements could be amazing,
perhaps even eliminating the often criticised coloration of
horn-loaded systems. The fitting amplifiers are out there waiting...
2A3 SET amps a try and you'll experience a new level of musical
reproduction. Less power is sometimes more. Music played with a 2A3
SET amp is more real, more involving, more fun ... and that's what
our beloved hobby is all about, isn't it?
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