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Audio by Van Alstine Fet Valve 550hc Hybrid Power AmplifierThe $ensible Sound Manufacturer: Audio by Van
Alstine, 2665 Brittany Lane, Woodbury,
MN 55125; 651/330-9871 http://www.avahifi.com/
info@avahifi.com As I mentioned in the Fet Valve preamplifier review elsewhere in this issue, several years ago I was able to spend some brief time auditioning the original Fet Valve preamplifier and power amplifier in my system, but until now we have never given a Fet Valve unit a full review, although we have reviewed several of AVA's solid-state amps and preamps, and even some of their tubed units. AVA power amplifiers have always represented good value; indeed, the Omega III 440hc amplifier, which Bruce Vigon and I reviewed in these pages a few issues back, has been my reference amplifier based on its sonic neutrality and output capability. The Omega III circuitry was so good that I believe there was some hesitation on the part of AVA in having their most expensive unit, the Fet Valve, compared to it. Recently, however, there was a revision in the Fet Valve amplifier design. The previous incarnation used a 12AX7A vacuum tube, but the newest version sports a 12AT7A. AVA claims that the latter tube has higher current gain, thus allowing then to change some circuit parameters for enhanced performance. The Fet Valve amplifier circuits are topologically similar to those in the preamplifiers. The tube runs in tandem with a MOSFET, and this tandem drives a power MOSFET that in the power amp then serves to drive the output MOSFETs, of which there are six per channel. AVA always devotes plenty of attention to power supply design, and there are banks of power supply capacitors at several locations inside the chassis. The tubes have a regulated heater supply, and there are isolated supplies for the various components of the front end and output stages of the active circuits. The Fet Valve 550hc is specified at 250 watts per channel at less than .01% THD. A lower-powered version, the 160-watt 350hc, is available at $1,499 for those with more modest power needs. It comes in the same chassis and has the same front end and output stage, but less ultimate voltage capability. The Fet Valve amplifier circuits are housed in the same chassis as the Omega III 440hc power amplifier. Vital statistics are 17"W x 13"D x 7"H, and weight is specified as 38 pounds. The front panel features only a power switch, and the rear panel, which is dominated by heat sinks, features a pair of heavy duty gold-plated RCA input jacks and two pairs heavy-duty five-way binding posts that will accept double banana plugs. For my listening sessions with the Fet Valve 550hc, I used the following equipment: Marantz CD-63 and Weltronics CD8 CD players; AVA Fet Valve EC preamplifier; and Legacy Focus, Biro technology L/1, and Platinum Audio Studio 1 loudspeakers. The Sunfire amplifier served as a foil. I mentioned in my review of the AVA Fet Valve EC preamplifier that the two components when used together struck me as utterly unflappable, but I have also stated that all power amps sound pretty much the same, so by now I am sure that some readers are either confused or gloating. Allow me, then, to offer some words of explanation. First of all, a well designed 250 watt per channel power amplifier should be unflappable. It should have adequate power reserves to drive most speakers with ease under most domestic conditions. The Fet Valve 550hc flies through this test with the greatest of ease. Whether rattling my walls playing majestic Michael Murray organ notes or reproducing the hush and thunder of my main man Mahler, the amplifier never seemed to break into a sweat (of course, even a 5-watt single-ended triode, no matter how inadequate to the task at hand, would not literally break into a sweat — I just threw that phrase in there to make my buddy Joe Cierniak break into a sweat). But let's take a specific example of what I mean. A recording that I really like is the 1989 DG CD of Neeme Jarvi conducting the Gothenburg Symphony Orchestra in the Shostakovich 15th Symphony, one of DG's best pre-4D recordings (as a bonus, it has one of the prettiest covers I have ever seen on a CD). I am certainly not going to claim this is the best orchestral recording I have ever heard, but it does some things really well, and I really like the music. Its main sonic flaw is a sense of harshness that creeps into the massed strings in some of the more frenetic moments. Here's where it gets interesting. It is my contention, and I will admit that it is only a contention, not a proven fact, that the Fet Valve EC preamp/550hc power amp combination makes this CD more pleasant than any other preamp/power amp combination that I have yet auditioned. I did not think the Transcendence Series Two/Omega III 440hc combination could be surpassed, but I swear the Fet Valve combo sails through this music with a more pleasant presentation. But that is not to say that they sound rolled off, or compressed. They just sound less... less "flapped." And that is what I mean by utterly unflappable. No, I am not basing my whole evaluation of this amplifier on the basis of what it seemed to me to do on one particular CD. As I said, I am offering my admittedly subjective but painstakingly formed impressions of its performance on that one particular CD as evidence to show why I am so taken by this amplifier's performance in my system. To my ears, the Sunfire did not do quite as well. Even if I am imagining things, and could not tell the two units apart under ABX conditions, there is the little matter of $374 — the extra cost of the Sunfire. On the other hand, the Fet Valve 550hc costs several hundred dollars more than the Omega III 440hc, which I also slightly preferred to the Sunfire; for most folks, the solid state AVA amplifier will be the better buy, one of the reasons I rated it a $ensible $tandard in Issue 64. I still maintain that all decent amplifiers sound virtually the same under most domestic conditions, and I believe that audiophiles would be much better off trying to improve the sound of their systems by moving their speakers around their room, auditioning alternative speakers, and above all by searching out good-sounding recordings, rather than fooling around with power amplifiers, preamplifiers, CD players, DACs, cables, magic bricks, etc. When push comes to shove, however, I also have to say that I have never heard better sound in my system than with the Fet Valve preamp/amp combination, which leads me to rate the AVA Fet Valve 550hc as a $ensible Choice for those seeking an unflappable amplifier capable of conveying sublime sonic subtleties in soul-satisfying splendor. - KWN
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