"ULTIMATE COMPONENTS"

VAC Renaissance
Thirty/Thirty Triode
Power Amplifier        

           
Capturing Musical Magic in  a Bottle
by Myles B. Astor

Listening to a "true" push-pull triode amplifier (300B, 211 or 845 based) can be a magical xperience.  The best of the genre are more musical, say, than a pentode but less colored than most single-ended amplifiers.  Unfortunately, the number of "true" push-pull triode amplifiers is extremely limited (most of todays triodes are strapped  pentodes) but they are worth tracking down.  One of the finest examples of that triode magic is Valve Amplification Company's (VAC) 300B-based Renaissance Thirty/Thirty triode tube
amplifier.

A COMMITTMENT TO "TRUE" TRIODE AMPLIFIERS

Kevin Hayes (along with his father Channing) began designing tube amplifiers because he
couldn't find a commercial amplifiers to his liking.  Hayes recalls that, "when our first
design turned out to be superb, I decided it would be a dream come true to work in an area
that I truly loved."  Thus in 1990, with Kevin as President and Channing as VP, VAC was
born.  VAC's first products were the PA45 and 90 tube amplifiers, which could be
switched between triode or ultra-linear operation.

 
WHAT'S THE FASCINATION WITH TRIODE AMPLIFIERS?

"True" triode amplifiers have always had a small, but faithful following.  Their tonality,
grain-free presentation and soundstaging are cherished by triode amplifier owners.  Yet
until recently, their low power (on the order of 10 watts), proved inadequate to drive the
vast majority of inefficient, audiophile type, loudspeakers.

When Hayes first heard a 300B, he knew that "this was simply too wonderful a tube to
leave languishing in low power amplifiers.  We had to design it into product that could
drive the majority of modern speakers.  And yet even we were, and continue to be,
astounded by result!"  Hayes prefers the 300B because "the triode vacuum tube is the most
linear amplifying device yet devised."  Triode tubes primiarly produce second order
harmonic distortion which is cancelled out using push-pull design topology.  This results
in a tube amplifier with extremely low higher and odd order distortion, two factors which
can detract from the musical experience.

 
VAC'S STATEMENT AMPLIFIER LINE: THE RENAISSANCE SERIES

Hayes describes VAC's Renaissance Series as a, "no holds barred" assault on sound
quality, incorporating everything they have learned about circuit topology, parts,
grounding and feedback.  All Renaissance amplifiers use the 300B triode tube, something
that might be considered an anachronism in this age of supercomputers.  The 300B
filamentary triode output tube was originally designed by Western Electric in 1935.

VAC's 32-watt per channel Thirty/Thirty is the "baby" of their Renaissance line - yet we
all know that there's a big difference between quantity and quality.  Hayes feels that "each
Renaissance amplifier has a slight personality of its own, but they are far more alike than
they are different."  Of the three, Hayes feels that the Seventy/Seventy amplifier most
closely reflects his personal taste.

The amount of care that goes into the design and building of these amplifiers is reflected
by the 1000 hours spent voicing the Seventy/Seventy, the first of the Renaissance line.
After that came the Thirty/Thirty, which required an additional 500 hours of voicing
before Hayes deemed it ready for release.  Interestingly, Hayes shared with me that the
parts selection that sounded best in the Seventy/Seventy and in the Thirty/Thirty are
different, particularly in the power supply.

 
TAKE NOTE

The Renaissance Thirty/Thirty's low power limits its applications.  The first speaker I
listened to the Thirty/Thirty on were the Martin-Logan reQuests.  Although the amplifiers
certainly drove the reQuests it was not a perfect marriage.  Overall, the sound was dark and
at times, a bit harshness crept it.  Audiophiles with power hungry speakers might be better
served by VAC's bigger Seventy/Seventy or 140/140 amplifiers.

Luckily I had on hand especially for occasions like this, the wonderful little Alon Adrianas
from Acarian Systems (which are quite happy with as little as 9 watts).  Now we were
cooking with gas!  All of the amplifier's musical strengths were revealed.  The Thirty/Thirty
is as a state-of-the-art high-end audio design should be: extremely revealing of different
source material without addings its own colorations.

Finally, I reviewed the amplifier in the zero feedback, RF grounded configuration and
using the 8 ohm tap.  Adding a few db of feedback tightens up the bass, but at the expense
of the midrange purity.  Another suggestion is to experiment with the grounding switch on
the back of the amplifier; with some speakers, there's more openness and ambience.

 
MUSICALITY, TONAL RESOLUTION AND COLORATION

Musicality is a term that is often thrown around, but seldom understood (yes, we can
groove to the radio, but that is not musical!).  For me, musicality is defined as the ability
to listen to an audio system for prolonged periods of time.  To begin with, a musical
product must excel at the retrieval of harmonic overtones.  Then, a musical  product must
exhibit freedom from electronic colorations such a grit, harshness and grain.  These big
three contribute to listening fatique and limit the amount of time one can spend listening
to an audio system.

But musicality can be overdone.  In todays world, musicality is too often synonymous with
complimentary colorations, meant to cover up flaws elsewhere in the music chain.  Many
so-called musical sounding pieces fail miserably when it comes to transparency (especially
in the midrange), low distortion, low level resolution, sense of ease and neutrality.  Over
the years I've stayed with push-pull pentode tube amplifiers because of their power,
neutrality and transparency and relatively flat frequency response into most speakers -
though I'm acutely aware of where they depart from musicality.  It's just that the pentode's
distortions are more acceptable to my ears.

 
THE HEART AND SOUL OF THE MUSIC

Then the VAC Renaissance Thirty/Thirty came along.  Here is an amplifier, much in the
mold of the conrad-johnson ART, that treads a careful line between musicality and
neutrality.  An amplifier that retains the richness of the real instrument without sounding
lush or soft in the upper octaves.  A midrange to kill for.  Inner details in abundance without
artificial enhancement.  The smallest click of the keys of a sax on Gene Ammons nice an'
cool (Analog Productions APJ038) or individual violins within the string sections on
Rachmaninoff's Isle of the Dead (EMI ASD 3254), are faithfully recreated.

Very few amplifiers surpass, much less equal, the Thirty/Thirty's ability to correctly
recreate instrumental tonality, especially in the ever so critical midrange area.  Take for
example Martin Simpson's Music for the Motherless Child (Water Lilly WLA-CS-44-CD).
The VAC amplifier brought this recording to life and I would give my right arm or first
born for an opportunity to hear the analog master tape!

The tonal distinctiveness between Simpson's steel guitar and Mann's pipa was rendered
with greater accuracy than any amplifier that I've had in the system.  The pipa exhibited
a twang (somewhat remininscent of a banjo) but sounded much smaller than the guitar.  There
was that "tonal completeness" commonly associated with tube electronics but without that
artificial exaggeration of notes or other aberrations in the harmonic decay of the instrument
(such as a thickness to early order harmonic and by contrast, a thinness to higher order
harmonics).  The amplifier's resolution ability was brought out by the degree of sonic
difference between the "Dives and Lazarus" vs. "The Coo Coo Bird." cut on the Water
Lilly CD.  With the latter piece, Simpson's guitar is much closer miked, revealing a greater
sense of detail and instrumental body.

 
PICKING UP THE PACE

Another area where the Thirty/Thirty really excels lies in its ability to recreate an
instruments sense of dynamic accents and dynamic range.  Dynamic from ppp to f were
recreated with incredible ease on Sympson's recording or the incredibly dynamic
"Movement 1" of Charles Wuorinen's Percussion Symphony (Nonesuch H7153).
Transients come from nowhere, without warning.  Cymbals are clean and without edginess.

The amplifier did run into a little bit of trouble at the extremely dynamic end of the
spectrum.  This wasn't  so much evidenced on cymbal work but a little further down the
frequency spectrum, say on the trumpet on the Isle of the Dead.  When pressed, the
trumpets sounded little thinner than they should.

 
UNLEASHING THE RECORDING'S MAGIC

Talk about the ability to recreate the original recording venue!  Talk about sound-staging
ability!  Talk about uncolored!  The Thirty/Thirty has it all.  While small speakers are
renowned for disappearing, the Adrianas simply weren't there!

Studio recordings sound more studio-like and hall recordings have their characteristic
ambience.  A favorite studio recording of mine is Portrait in Jazz: Bill Evans' Trio (OJC
088).  With the Renaissance Thirty/Thirty, the piano, double bass and drums stand out
within the studio.  There is a good sense of transparency but I feel this could be slightly
improved with a touch more openness in the lower treble/upper midrange area.

The piano sounds far more realistically sized.  Scott LaFaro's double bass exudes a sense
of internal volume and fullness.  Listen to the difference in the sound of double basses
between the DDC reissue of Oscar Peterson's West Side Story (DDC LPZ2021) and the
Bill Evans recording.  Ray Brown's bass sounds more ill defined, verging on a one note bass
sound, than does LaFaro's bass.

The most astounding characteristic of the Thirty/Thirty (and other  push-pull triodes) is the
sense of instrumental palpability.  You feel like you can walk up to the instrument and grab
them away from the musicians.  Instruments are clearly localized and the air or ambience
around each instrument is clearly separated from the neighboring instrument.

Two minor shortcomings of the Thirty/Thirty are that the low frequencies could be a hair
tighter and faster . Drums and tympani on the Wuorinen recordings have their proper
weight but could use a touch more impact.  The speed issue may not be objectionable to
classical or jazz music fans, but those who listen to hard hitting rock and roll may find the
amplifier makes the music slightly too pretty.

 
HOW MUCH POWER IS ENOUGH?

I have to admit that the prospect of hearing the Thirty/Thirty's bigger brothers is especially
enticing especially on something like the Martin-Logan reQuests.  While bigger may not be
better, I'd sure like to hear them.
 

On the right speaker, the Thirty/Thirty is a magical amplifier.  If there's an overall
weakness to the Thirty/Thirty, it's that the midrange is so good, that it overshadows the
amplifier's performance at the extremes, particular in the low end.  There are few
amplifiers with a more realistic midrange tone, sense of space and instrumental palpability.
Face it.  If you don't get the midrange right, the rest is for naught.  If you regularly attend
live music, you'll really appreciate the VAC Thirty/Thirty's faithfulness to music.

VAC Renaissance Thirty/Thirty Triode Tube Amplifier, Valve Amplification Company. Designer: Kevin Hayes.
Website:www.vac-amps.com.

MEET THE DESIGNER

The Renaissance Thirty/Thirty produces a grand total of 32-watts/channel from a pair of
300Bs (VAC imported Chinese 300Bs) per channel.  Their exceptional linearity, even when
compared to other triodes and to triode-strapped pentodes or beam power tubes
(EL34, KT88), was one of the main reasons VAC decided to use 300Bs in the Renaissance
amplifier series.  This linearity is clearly demonstrated when plate current is plotted as a
function of grid voltage for different tube types; the 300B displays a noticeably  straighter
and more uniform characteristic, in essence a truer transfer function for the signal.

According to Hayes, "the greatest possible linearity and purest fidelity results from
avoiding cut-off and saturation."  By choosing to operate the Renaissance Thirty/Thirty in
Class-A1 mode, the 300B tube never reaches cut-off (the region at the lower end of the
dynamic characteristic curve where the tube ceases to conduct currect) at any time at any
levels up the maximum it operates at.  Each 300B is self-biased and protected by a special
"sentry" circuit that senses a runaway tube without any electrical connection to the signal
path or B+ rail (which adds grain).

Another reason is the 300B's low impedance.  A 300B delivers exceptional performance
at less than 450 V while comparable triodes such a 845 or 211 typically require 1,000 or
more volts.  The 300B's low internal impedance and voltage requirements allow the
construction of a superior output transformer design with less step down and insulation,
allowing better coupling to the loudspeaker.  In the case of the Thirty/Thirty, the 14 pound
output transformer uses 21 sections and bifilar winding with match points for speakers from 1
to 8 ohms.

The final reason for selecting the 300B is related to the question of static vs. dynamic
damping.  Normally, the best way to achieve a high amplifier damping factor is through
the use of negative feedback which Hayes feels, "entails major comprises.  Negative
feedback may reduce distortion but it multiples the order.  Higher damping (though the use
of negative feedback) factors don't necessarily translate into better speaker control."  While
conventional wisdom is that greater control is achieved when the amplifier "corrects" for
back EMF generated by the loudspeakers extraneous motion or overhang, Hayes points out
that the problem with this theory is that, "the error signal is in itself erroneous and is not
representative of the sound being produced."  For example, the acoustic output and the
cone motion may differ somewhat.  Or the voice coil motion and overall cone motion differ
due to flexing and breakup.  Another serious consideration is the voice coil's large
inductance phase shifts the signal.  Finally, there's the problem created by the when the
crossover network further phase shifts the signal and mixes in the different back EMF
from other drivers, resulting in a summed signal that does not represent what any one
driver is doing.  So Hayes feels that, "the best overall speaker control and sound fidelity
results from the highest damping obtained without negative feedback and the use of highly
linear triodes with low impedance such as the 300B."

The Renaissance  Thirty/Thirty's input circuitry is a direct descendent of the original
Williamson circuit.  This gives pure, direct coupled, balanced input amplification and phase
splitting.  The circuit is completely push-pull save for first 6SN7/5692 octal twin triode
which VAC operates under conservative conditions to minimize distortion.  According to
Kevin Hayes, "the modified Williamson phase splitter is unique in that the same electrons
flow through a single triode creates the antiphase push and pull signals, resulting in a
precision and balance possible up to several megahertz."

 
Reprinted with the permission of Ultimate Audio, One New York Plaza, Suite 214, New York, NY 10004.
For more information visit their website at www.ultimateaudio.com.

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