VT100 Mk.III Review
by James Leahy
The Audio Research VT100
Mk.III is the last of the VT100 series and is rated at 100 watts per
channel as it's name would suggest. I used this amplifier in my
system for a number of years as my main reference amplifier and have
been very pleased with it's performance. It uses eight Svetlana 6550C output tubes
and four 6H30 tubes for the input/driver circuit. There are twelve
Nichicon capacitors that contribute to this units lightning fast
frequency response and dynamic impact. With a total of 540 Joules of
energy storage on board you will not believe the bass extension of
this King of valve amplifiers. The VT100 series was first introduced
in 1986 and has the unofficial title among the people in the know as
the most popular high-end valve amplifier of all time! Such is the
heritage of this product there is really no better value on the
The construction of the VT100 is really second to
none in it's class, with 'tank' like build
construction and packed full of military spec electronic components.
When only the best will do accept no substitute! The front panel shows
off Audio Research's trade mark slim handles with a simple toggle power
switch for operation.
the back, it is again a well laid out affair with 4 & 8 ohm loudspeaker
There is a choice of either 'Single Ended' or
'Balanced' inputs to select from. The Mark. III version of the VT100 has
introduced a simple rear switch that renders the need for shorting pins
in the Balanced input unnecessary if the Single Ended inputs are to be
used. The rear panel is modified (and a sub-board added, see picture
right) for the 12V trigger to turn the amplifier on via a remote control
Audio research pre-amplifier.
The circuit is of a fully Balanced design and is
dual mono in construction. The main internal circuit boards for the left
and right channel are mounted vertically and are well laid out with
plenty of space for maintenance and cooling. There is one 5" muffin fan
provided at the bottom of the unit that is automatically speed
controlled so the amplifier is constantly operating at the correct
temperature. The factory Svetlana 6550C tubes are the best I have used
and I would not advise changing to any different brand or spec units.
Just like it's bigger brother the VT200, I would
advise using this amplifier only on an adequate stand that is
specifically made for maximum ventilation. The VT100 does run warm but
if there is space under the amplifier for sufficient airflow the working
temperature can easily be kept under control.
The biasing procedure for the VT100 Mk.III could
not be easier. The amplifier is equipped with four trim pots and each
matched pair of output tubes is adjusted with it's specific trim pot
that is located under the top cover in the upper left hand corner. The
test points are equally easy to find and access being along the top edge
of the circuit boards on each channel. Due care must be taken to use the
necessary equipment with biasing any high voltage component and if you
are not thoroughly comfortable in your electronic ability I would advise
to seek assistance from a qualified technician as it is better to be
cautious rather then sorry. +320VDV can hurt some.
The VT100 Mk.III is more detailed and gives a
more forward presentation then the older Mk.II version which has a
more relaxed and tube like midrange. The Mk.III is a very revealing
amplifier and will show up any harsh or unflattering front-end
components in a flash. Be warned. It retains all of the tube virtues
in it's harmonics and timbre but couples them with a more exact
soundstage, never before seen from Audio Research. This amplifier is
the primary product that has taken the company in a new direction.
Being one of, if not THE first one of their products to utilize the
6H30 or 'Super Tube' to some.
Spinning Eric Clapton's - 'Backless' album
(RSO Records, 1978) the fine fragments of detail the Mk.III can show
up is staggering. Not only is the sound full but the soundstage is
wide also. It just makes you want to crank the volume to full, so
enjoyable is the synergy of speed and rhythm. The top end is not
harsh or fatiguing to listen to for extended periods but the
layering is not your typical valve amplifier's style. The treble is
a touch on the sharp side of neutral and very extended compared to
the VS110 and VT100 Mk.II.
The soundstage is very deep and has great
width with each track having it's own layer and position without
encroaching on any other part of the image. The central image of
this amplifier is one of the best I have encountered. It is for
precision image freaks. The low bass extension is the best I have
ever heard from a 100 watt stereo valve amplifier, period. What you
are used to in the way of powerful full bass will be redefined if
you have never heard this amplifier before in your system and are
used to the common spongy soggy bass tube amplifiers sometimes have.
I found there is a hint of dryness in my system with this amplifier
in the lower midrange with some recordings that may tend to show up
your systems brighter side but this was only evident while testing a
digital source. You should be using vinyl anyway.
As for punch and slam the VT100 Mk.III has
plenty of both on tap for even the most hungry of users. This is no
slouch of an amplifier when it comes to it's speed of delivery. I
would advise matching this amplifier very carefully with what ever
pre-amplifier you choose to use with it. The older Audio Research
pre-amplifier's with 6922 tubes tend to complement it's style best
in my opinion. Specifically the Audio Research LS15 was great and
the SP15 also worked very well.
Associated review Equipment
Line Stage: Audio Research LS26
Audio Research PH5
ScanSpeak & Vifa Custom
Cartridge: Ortofon MC Jubilee
Subwoofer: Velodyne HGS-15