Audio Research VT100 Mk.III  Review

by James Leahy

 

                                                                     Introduction

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 market today.

 

 

 

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. Around the back, it is again a well laid out affair with 4 & 8 ohm loudspeaker binding posts.

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.

 

 

 

Sonic Evaluations

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

  • Phono Stage:      Audio Research PH5

  • Speakers:           ScanSpeak & Vifa Custom

  • Cables:              Neotech

  • Cartridge:           Ortofon MC Jubilee

  • Turntable:          Rega P7

  • Subwoofer:         Velodyne HGS-15

  • CP Player:          Sony SCD-XA777ES