U.S. Patent awarded for VAC iQ Continuous Automatic Bias Circuit

On June 10, 2014 the U.S. Patent Trademark Office (USPTO) awarded patent 8,749,310 for the VAC iQ circuit. This is the only automatic bias circuit capable of holding steady the true underlying DC idle point of the output tube (or transistor) in the presence of varying musical signals. It’s quite a breakthrough, and the results are, somewhat surprisingly, quite audible.

New review of the VAC Phi 200 … “revelatory”!

In the September 2013 HiFi World magazine, reviewer & musician Rafael Todes finds the “amplifier of his dreams” – the VAC Phi 200!

Mr. Todes, a member of the famous Allegri Quartet, notes the “VACs are quite simply extracting levels of detail of which I was hitherto unaware” and “have an extraordinary ability to resolve detail like no amplifier/s I have heard before” which leave him “many yards closer to the goal of live music making recreated.” He concludes that “they are a “must hear” for anyone searching for the ultimate in valve amplifiers.”


Full text:

The Valve Amplification Company is well known to the audiophile community in the USA, but is more of a rarity on this side of the pond. Founded in 1990 by a father and son team of Kevin and Channing Hayes, it is based in Sarasota, Florida and employs around 20 people.

VAC initially made its name for winning the contract to re-issue the Marantz Classic series (Model 7, 7C, 8B and 9). It was with one of the latter that I became acquainted with the brand, having heard the 8B, I was struck by the sweetness and openness of the sound, which retained faithfully the spirit of the original.

The amplifiers arrived later than intended: There is currently a twelve week wait for new stock. Each product that leaves the VAC factory is personally voiced and signed off by designer and CEO Kevin Hayes. It is an artisanal product, not a mass market affair with very high levels of quality control. Typically, between 500 and 1000 listening hours go into developing a new model. The Phi 200 is actually the entry level power amplifier in the range, with several models sitting above it in VAC’s offering.

The Phi 200 can be operated as a stereo amplifier in its own right, or can, by the flick of a switch on the rear panel be converted into a monoblock, so the power output doubles from 100WPC to 200WPC with the addition of a second unit. This gives the user the opportunity to upgrade seamlessly, without having to replace the existing unit. Another pair of switches at the front alters between single ended and balanced operation. For the bulk of the listening, I used single ended operation and a pair as monoblocks.
Biasing is achieved by reference to discreet amber indicator lights, on the top panel. I found the bias to be remarkably stable after the first few hours. Each monoblock uses 4 KT88′s and 4 SN7′s. VAC supply selected and tested Shuguang valves which are their valves of choice. The transformer technology is traditional but well honed. The transformers themselves are massive, and are stick as opposed to bobbin wound. The amplifier has a damping factor of around 2 which is stable across the frequency spectrum, and uses only small amounts of negative feedback.

The unit borders on the utilitarian in looks. Weighing in at 40.9kg, the amplifier is lighter than some, and is a relatively easy one-man lift. The fascia comes in a choice of black or silver, and is 9.5mm aluminium, finished in lacquer. An illuminated blue VAC logo can be switched off on the rear panel, if so-desired. Its looks in no way belie the extraordinary quality of sound that emanates from it.

Sound Quality

Listening on my Inspire Monarch turntable, SME V arm, and Icon Audio PS3 phono stage, to Dvorak’s 7th Symphony, the Scherzo, the Concertgebouw Orchestra under the baton of the recently late Sir Colin Davis on Philips, this movement has an almost morse code-like rhythm to it and is a recording I know intimately. The music is fabulous, but I’ve always been left underwhelmed by what I thought was a mediocre recording. The VACs make it sound utterly different to what I’ve heard previously. They take a stiff brush to the grungy midrange, resolving a staggering quantity of new detail, and creating an orchestral holography the likes of which for me is again new. The morse code is rapped out with consummate panache, creating the taut rhythmic structure that propels the movement to its breathtaking climax. It sounds almost unfamiliar due to the increased detail I’m noticing. The string section has tremendous depth and clout, the basses go down low, with not only a solid state-like grip, (unusual for valves), but also with etched texture which is revelatory.
The climaxes are effortless, the sound is vibrant, engaging and powerful.

The famous Allegri Quartet (way before my time in the quartet!) recording of the Elgar Introduction and Allegro, Barbirolli on HMV, recorded in 1962 is supposed to be an all-time classic, and whilst the musicianship is stellar, the recording has always left me a bit confused. The VACs have the resolution to hear the tiniest detail amongst the quartet of soloists, and to place them accurately in the enveloping orchestra in a way I’ve not heard before. The simpler microphone techniques used then, together with a recording, not mastered to within one inch of its life makes this a difficult play for all but the best. The VACs effortlessly sort out the confusion and chaos, and leave in their wake a compelling musical argument in this, one of the finest English string orchestra pieces.

Turning to some live radio, using my valve Magnum Dynalab MD90TSE tuner, with a live link up to the Met in New York, Wagner’s epic Siegfied sounds like I have never heard one of these broadcasts sound. Normally I just about get the energy and excitement of these world class performances, but the stage sound is slightly constricted, the orchestra typically sounds a touch boxy. With the addition of these VACs to my system, the midrange boxiness disappears, the stage dimensions are blown outwards, and there is a palpable feeling of really being three thousand miles across the pond, in the Met itself. The voices are commanding, nuanced, free of the distortion I have heard from lesser amplifiers, and the sheer weight and gravitas of this amazing work erupts. The orchestra layers with the singers in a way I have not heard before. Each instrument in these vast forces has a perfect place in space, both horizontally, laterally, as well as texturally. The VACs are quite simply extracting levels of detail of which I was hitherto unaware, particularly on an FM broadcast.
How does the sound compare with only one unit in stereo, and not two monoblocks?
Still mouthwateringly good, but a bit less of a generous soundstage, and less of a feeling of authority. Listening to a live BBC broadcast of the rarely performed Schumann 2nd Symphony, there is a more compacted feeling to the orchestra, as the amp uses a greater proportion of its resources to drive the B&W802d’s. Twice as good, maybe not, but worth it to the luxury it brings to the sound.

These mono blocks have an extraordinary ability to resolve detail like no amplifier/s I have heard before. Although they can make even the most badly-recorded record sound good, they are highly critical of poor sources, and really shine when feed with the best quality material available. They seem to exacerbate differences between the mediocre and the excellent, and even highlight the minutiae of cable differences. I find it very difficult to ascribe a particular sonic signature to them, as they seem to be as chameleon as any piece of audio I’ve ever encountered, taking on the character of the source, and not impressing their own version of events. They don’t have that gloopy valve sound that can sound attractive, but is not particularly real. They have bass command that is up there with the best solid state amplifiers I’ve experienced, along with the liquidity, transparency and beauty associated with the very best valve amplifiers. It leaves me many yards closer to the goal of live music making recreated, and they are a “must hear” for anyone searching for the ultimate in valve amplifiers. It however leaves me with great curiosity to know what the next model up sounds like!

Price £8750 for single stereo unit or £17500 for 2 monoblocks.
Distributed in the Uk by The Music Room
4 Park Circus
Glasgow G3 6AX
0141 333 9700


Inspire Monarch Turntable
SME V arm
Ortofon Cadenza bronze cartridge
Icon Audio PS3 Special edition Phono stage
Weiss DAC202
Chord Indigo Plus cable
Townshend Allegri Preamp
B&W 802d Speakers
Magnum Dynalab MD90SET Tuner
Telerium Q Speaker cables

More Praise for VAC at Newport

Good report From Stereophile about our VAC Statement components at the recent Newport Audio Show:

“In the best of all possible worlds, the system would still be up and running two weeks after the show closed, Southwest Airlines would be all too eager to fly me to and fro for free … some of the best sounds at the Hilton.”


Marjorie ‘Margo’ Hayes, the Voice of VAC

With great sadness we announce that Margo passed away on Saturday morning, May 25th, at the age of 91.

Margo is the mother of VAC founder & president Kevin Hayes. She was present when VAC was conceived, and answered the telephone and kept the books for the new company. For most of the past 23 years, when you called VAC, you heard her voice.

She loved VAC and loved our customers, often taking a personal interest, remembering the names of family members and various situations.

On March 10 she had suffered a collapse which necessitated surgery and time in the hospital and rehab. She was released April 10, and returned to VAC on April 15, not missing a day through May 24.

As much as she loved VAC and her children, the truth is that she was ready to ‘go home’. A firm Christian, she has every confidence of where she is going, and of seeing so many loved ones who went before her.

I love her, and she will be missed more than I can say. Truly, I hope to see her again when my time comes.

Kevin Hayes / VAC

Letters: VAC Phi 200 Monoblocks for Steve Hoffman

“Santa is visiting really early this year. Or should I say Kevin Claus? Kevin Hayes is one of my favorite top end audiophile gear designers and his company (VAC) is tops in vacuum tube stereo. He is sending me a new pair of the phenomenal VAC Phi 200 monoblocks for my studio. Just in time for mastering BOB DYLAN’S GREATEST HITS, VOL. II. The Phi 200 is a stereo amp with 100 RMS watts a channel but with the flick of a switch, it’s 200 mono watts. A pair will be just right for my needs. Once again, Kevin Hayes comes through for me. Much appreciated!

Kevin Hayes, I’m so appreciative, thanks so much. The Phi 200′s sound truly amazing. The Phi 200′s sound truly meaty, I mean, nicely authoritative. Wonderful inner detail without being bright or harsh. Makes everything sound better yet still accurate to the sound of the master tape. Will make my job a whole bunch easier. THANKS, KEVIN!!!! Just in time for Dylan mastering next week.”

Steve Hoffman

February 26 at 8:13pm · Edited · Unlike · 1