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VAC Phi 200 Tube Monoblock Amplifier Review

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Reading required

Even an Owner’s Manual can reflect on the nature of the designer. The Phi 200’s manual describes features and has no diagrams. It is anticipated that someone who lays out long green for a premium instrument will care enough to read what and what not to do with the amp. Hence, a thorough discussion of the operations in the manual, a walkthrough if you will, describes the experience of using the Phi 200. Starting with the safety notices on the first page, tidbits of advice assist the new owner, among them:

  • Avoid power conditioners that float the ground pin.
  • A 12V trigger cable can be used to turn the amp on and off via external device.
  • “Pay close attention to power quality, and be aware that different power cords can alter the sound.” (Bravo! An amp manufacturer who acknowledges the critical nature of power cords!)
  • Discussion of break in period – approximately 200 hours.
  • Description of the appearance of tubes operating normally, as well as ones which are “running away”, being destroyed due to excessive current when seated improperly or defective.
  • Expectations regarding tube life and quality, and VAC selection of its tubes for use with the Phi 200, as well as a list of equivalent tube numbers for tube rolling.
  • Explanation of Impedance Matching, including the option of using two different impedance output posts for bi-wiring speakers (However, use of 4-8 Ohm posts are required for Mono amp mode with low efficiency speakers like ESLs).

As one reads, it becomes clear that Kevin anticipates the new owner to consider his amp an instrument for fine music reproduction. Years of experience as a designer and music enthusiast are coalesced into the Manual, and I recommend careful reference to it.

“VAC Facts”

VACPhi200-7

Before delving into discussion of the sound of the Phi 200, I would first like to stimulate your intellect as to the quality of the Phi 200 and VAC gear in general by alluding to what I call “VAC Facts”. These are lesser known packets of knowledge regarding development of the VAC Phi 200 amplifier. These VAC Facts are not merely for entertainment; they are stepping stones to understanding the radical commitment of Kevin Hayes and VAC to bring you the ultimate in audio componentry. Good sound needs to rest on good design principles and good execution. The VAC Facts speak to these and beckon rationally to those who are seeking ultra high-end electronics. As you read them, these testaments to quality will lead you to conclude that VAC authentically cares deeply about product integrity and sound quality.

VAC Fact: The Phi 200’s name is not mysterious, as Kevin merely followed convention in audio circles by using a letter of the Greek Alphabet. It may not be an exaggeration to say that half the Greek alphabet has been sourced to name audio components and technologies.

VAC Fact: The company builds “Stereo Beam Power” amplifiers. This is a reference to avoidance of standard Tetrode tube designs. According to Kevin, a “beam tetrode” or “kinkless tetrode” causes the electrons to flow in sheets or vertical beams, while repulsing secondary electrons. The design allows for removal of the third grid inside the tube, leaving the anode and cathode. The design is more efficient and yields greater power output than a pentode tube. The KT66 and KT88 are the most successful implementations of this technology in terms of audio quality.

VAC Fact: The Phi 200 is a proudly hand built American product. However, it uses a new twist on the power tube, the KT88-SC. Chinese tube maker Shuguang makes it and the 6SN7, both of which are deemed better than NOS tubes! Kevin states that they are notable not only for superb sound, but superior longevity as well.

VAC Fact: The Phi 200 was introduced at the 2008 Rocky Mountain Audio Fest (RMAF). Two revisions have been introduced, namely the addition of the MONO switch, and a LOGO ON/OFF switch.

VAC Fact: The KT88-SC power tubes operate in ultra-linear mode and feed two 15-pound VAC output transformers based on classic transformer design.

VAC Fact: Kevin adheres to a “divide and conquer” philosophy when designing higher-power amps. Per Kevin, “Most designers go for larger parts; I think more along the lines of parallel processing (which, of course, is now all the rage in DACs and computing).” The Phi 200 in Mono mode is very much like his design for a stand-alone mono amp, and benefits from the design of the Phi 300 which was a Stereo/Mono design.

VAC Fact: Kevin shares, “If there is one thing I have learned in twenty-plus years in audio design, it is not to prejudge things….. I never assume that a particular tube type, capacitor, circuit topology, etc. must be the best. I do not let my theories tell me about the real world; I try to let the real world correct and refine my theories. To that end, we conduct frequent R&D projects that run contrary to our assumptions. In this way, we learn, grow and produce much better instruments than we could have imagined.” A sign in VAC’s listening room reads: In theory, there is no difference between theory and practice. But, in practice, there is.

VAC Fact: The cost is similar to acquire one Phi 300.1a or two Phi 200. Which would yield superior results? According to the designer, “I think the pair of Phi 200 would have a slight edge with regard to detail, extension and dynamics. Ah, but then there are the Mono 300’s…”

VAC Fact: The three transformers of the Phi 200 weigh more than half of the amp’s total weight.

VAC Fact: The Phi 200, like all VAC products, is designed such that you can leave it to your grandchildren in your will. It is crafted to last. The anticipated first major service is the refreshment of the power supply capacitors – after approximately 40-50 years!

VAC Fact: There are eleven sets of speakers currently being used at VAC for the voicing process: five sets of dynamic, three sets of full-range electrostatic, one set of hybrid electrostatic, and two sets of horn speakers! The amp was not designed solely to drive the King ESL, but the King was used in the voicing of the Phi 200. Improvements to a VAC design are only accepted if it sounds better with some or all speakers tested and worse with none.

VAC Fact: The voicing process may take Kevin and VAC engineers up to 1,000 person-hours in some cases; that’s beyond the time taken to get the amps to measure well on the bench! If Kevin does not approve the sound of an individual component (he listens to each one), it does not ship. Production of certain models has ceased at times for up to two months while tracking down a variance in vendor’s products, such as wires or capacitors.

VAC Fact: The voicing process of the Phi 200 was thought to be done until a pair of Zingali horn speakers were hooked up. Through the Zingali, the circuit sounded bright, yet soft, which called for an adjustment to increase the control and precision of the top octave. The cure was affected, but the change was completely inaudible on a pair of Thiel speakers.

VAC Fact: Kevin’s opinion of Class D amplification, “… we have neither seen nor heard anything in theory or in practice to suggest that Class D would be a good idea with regard to sound quality.”

VAC Fact: At the upcoming 2011 Consumer Electronics Show (CES) in Las Vegas, VAC will introduce the Phi 200i, an integrated amplifier mechanically like the Phi 300.1a, but with 110 wpc. It is designed to overcome many of the shortcomings of integrated amps. It uses two separate power transformers, one for the pre and the other for the power amplifier. It will include a genuine line stage as opposed to being an amp with a volume control, and phono stage. Kevin says, “It should be roughly equivalent to the combination of Renaissance MkIII Preamplifier and Phi 200 Amplifier.” Also on the horizon is the Sigma 160i integrated amplifier (see, another Greek letter name) which will look similar to the Phi 200 and cost approximately $9,900.

3 Responses to VAC Phi 200 Tube Monoblock Amplifier Review


  1. Ellen says:

    Hello, I enjoyed your review. I am in the middle of looking for and listening to amps. I am a bit scared by tubes but also drawn to their sound. I heard the VAC Sigma 160i SE and really liked it. My funds are limited but the question is whether I should save up a bit more and go with the Phi 200 and what pre-amp? Any thoughts. It will be paired with Wilson Sabrina speakers. May 7, 2016

  2. Jón Kristmann says:

    Halló ég er með Yamaha ns 500 og Devialet 200 frábært sánd , er einnig með First Sound paramount mk 2 langar að spyrja virkar VAC phi 200 eða phi 300,1 við hann. kveðja jkþ ?

    [English translation] Hello I have the Yamaha ns 500 and Devialet 200, also with First Sound paramount mk 2 would like to ask active VAC phi 200 or phi 300.1 to it. greeting jkþ?

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