Part-Time Audiophile

Review: Audio Research VT80 Foundation Series power amplifier

Audio Research VT80 Power Amplifier.

By John Richardson

I miss Sam Tellig. I always read Sam’s column in Stereophile as soon as the newest edition hit my mailbox; I found him to be an entertaining and informative writer. It was great to read about his European adventures, and the offbeat audio personalities he hung out with (Roy Hall included). I also learned an important lesson about audio reviewers from Sam: We don’t always agree.

This lesson I learned the hard way. I once (long ago) purchased some gear based solely on Sam’s reviews. I won’t mention the makes and models here, but the stuff sounded awful. Well, maybe not awful, but certainly not very good in any musical sense. We obviously don’t hear things the same way, or perhaps we just diverge on what makes us aurally happy. All this happened long before I became an audio reviewer, but I learned from the experience that reviewers are merely human, and that we do our best to convey what we hear and experience to our audiences. We’re not infallible prophets of the audio world. We’re human.

Sam was a master of analogy. One of my favorites was something he once said about comparing lovers of different amplifier technologies to dog or cat people. It went something like this: dog people like tubes; cat people prefer solid state. There are lots of ways I could take this as a self-described cat lover. Um, solid state implies sand, and cats like to take care of their business in the sand. Or how about this one… cats are cold, heartless, soul-sucking creatures, much like solid state gear. Actually, I think Sam was really referring to the care, feeding, and upkeep thing. People like me prefer cats because you pretty much feed and water them, keep their litter boxes somewhat clean, and give them occasional attention, but only when they want you to. Disposable pets, as my dad used to say (though I wouldn’t consider a Pass Labs XA250.8 exactly a disposable item). Dogs, on the other hand, well, we know what dogs require to stay happy Much like the care and feeding of tube amps, right?

I suppose there’s some essence of truth to all of this nonsense. Scot Hull has a friendly dog and digs tubes, while I have a somewhat normal (um, neurotic) cat, and I most definitely gravitate toward solid state.

Introducing the Audio Research VT80

Now, back to the real topic at hand: vacuum tube amplifiers. I’ve been involved in high-end audio for a long time; I feel that I can honestly say that I’ve had plenty of exposure to valve amplifiers. I’ve spent time with single-ended triode flea-watt amps, as well as more powerful pentode-based push-pull designs. I’ve reviewed my share of tube amps, and I’ll even admit that it was an all-tube system that got me initially hooked on the high-end. It’s great, great stuff, in an altogether bigly way. But here’s my admission: I’ve never, in over 25 years in this wonderful hobby owned a vacuum tube amplifier (though I have had a couple of tube preamps). I can’t exactly say why. Maybe it’s the danger associated with those hot, glowing bulbs of glass protruding from the chassis like the menacing fingers of Beelzebub. Or perhaps it boils down to simple laziness. You know, voltage biasing and worrying about tube life and replacement. This stuff could get expensive, not to mention become a real pain in the butt. Heaven help you if you’re a bit on the obsessive-compulsive side, wondering about just how much your amp’s sonic goodness has decayed every time you turn the damn thing on, thus wearing down the tubes! I guess I’m kind of a flip-the-switch-and-listen sort of guy.

Enter the subject of this evaluation: Audio Research’s new entry-level amplifier, the $8,000 USD VT80, part of the company’s new Foundation Series of components. According to the company literature this is an intro-level amplifier meant to coax solid state folks like me over into the realm of vacuum tubes. Now that I’ve spent some quality one-on-one with this honey of an amp, I can say that those tubes do call out with a particular siren song.

The big guns: KT120 power valves.

Lots can be said about Audio Research (the company), as it is definitely one of the original grande dames of modern American high-end audio. Started way back in 1970 by William Zane Johnson (not the Johnson of competing company Conrad-Johnson), Audio Research has introduced ground-breaking designs over and over again, many of which remain mainstays in audiophile systems many years after their initial purchase. I have a friend with a serious megabuck system who has used Audio Research exclusively for his amplification needs for at least the last 20 years, and he has no desire to stray from the brand. In fact, he is presently in the market for their upscale Reference Line components Audio Research gear is well-known for its excellent build quality and longevity under years of strenuous use. It’s also still manufactured here in the U.S.A., specifically in Plymouth, Minnesota.

Perusing the well-written user manual, I see lots of things for someone like myself to appreciate about this amplifier. One feature that caught my eye immediately was that the VT80 uses a new and proprietary auto-biasing circuit which in turn makes the tubes themselves “plug ‘n play.” While I am a tinkerer, I don’t particularly want to spend time messing around with a volt meter and a screwdriver, setting the tube bias “just so” every time I turn the amp on. I realize that this procedure is part of the ritual for some audio enthusiasts, but most of us solid state guys and gals just don’t want to be bothered with it. Another design aspect that appeals to folks like me is the counter on the rear panel that tells the user how many hours are on the tubes. Audio Research recommends replacement of the KT120 power tubes after 2,000 hours and the smaller 6H30 driver tubes after 4,000 hours. Keep track of the counter and change tubes at the recommended intervals; it’s as simple as that for those of us who don’t want to worry ourselves silly guessing about tube life and sonic degradation.

Also, I’m pleased that Audio Research has made the decision to use relatively common and obtainable tubes in this design I’m sure some of us have had the following conversation, either in real life or in our worst nightmares:

Cheesy Salesperson: “So I have here the best tube amp known to man, and it uses the super esoteric Blue Flame X-1000 vacuum tube, which was only manufactured in New Jersey between 1925 and 1930 as a radio transmitter tube…. It’s absolutely awesome!”

Me: “So what do I do when the tube dies?”

Cheesy Salesperson: “No problem. We’ve hit upon a cache of 40 NOS tubes, so we’re producing a limited run of 20 amps so that each amp will have a spare tube that we can supply at a later time.”

Me: “Cool So what do I do when the spare tube goes?”

Cheesy Salesperson: …. crickets…. the sound of silence… and finally, in a low, evasive tone, “Oh, well there’s always eBay.”

No thank you.

Now that I’ve determined that the Audio Research VT80 is a potential keeper for even those poor souls leery of tubes, here are some relevant specifications: (from the manual) power output is 75 watts per channel, presumably into both the four and eight ohm taps; power bandwidth is seven Hz to 60 KHz (measured at -3dB @ 1 watt); input impedance is 300 kohms (balanced) or 150 kohms (single-ended); output is non-inverting Also, up to 15dB of negative feedback is employed, and the amp has a slew rate of 10 V/microsecond with a rise time of four microseconds. Channel separation is 112dB, with a signal-to-noise ratio also of 112dB. These are pretty decent specifications for any high performance amplifier, suggesting that the VT80 should perform at a very high level of listener satisfaction.

Upon first unpacking the VT80, I found myself encouraged by both the heft and obvious build quality of the amp. Like other Audio Research gear I’ve seen in the past, this one looks like it’s meant to make it all the way to (and possibly beyond) the apocalypse. I also find the amp quite attractive, with its neatly proportioned face plate festooned with classic metal handles, on through to the rest of the well-constructed chassis, from which the tubes and transformers poke forth. This piece of gear inspires confidence, even from a self-proclaimed vacuum tube scaredy-cat like myself. The tubes themselves came separately packed in another box and were obviously labelled as matched pairs. Really, no room to screw this up, right?  Installation of the tubes was also easy-peasy, as I just turned each tube in its socket until the pins matched up and slid into their slots. After making all proper connections as indicated in the manual, I hit the power switch on the front panel. A little green LED flipped on, and the tubes started to glow warmly. About a minute later, I started up some tunes, and the music flowed. Simple as that…

The business end.

The VT80 accommodates both balanced and single-ended inputs. My first try was using the single-ended option, feeding the amp’s inputs from my Linear Tube Audio MicroZOTL 2.0 serving as a preamp. The music was lovely, but I noted an audible hum coming from the speakers when the setup was idle. While barely noticeable when the music was playing, I was vexed by the hum merely because I knew it was there, much like a pesky mosquito buzzing around my head on a hot night. The hum was probably the result of a ground loop issue which I tried to track down and remedy, and which I eventually got tired of doing. Why not try the balanced inputs?  This I did, running a set of interconnects directly from the balanced outputs of my Antelope Audio Zodiac DAC. Ahhhh, heaven. No hum whatsoever… The amp was quiet as a church-mouse. As I found the gain more than suitable for any and all speakers I used with the VT80, I felt no need to re-investigate the single-ended option or use a separate preamp.

Sonic Impressions

Balanced or Single Ended awaits.

My intent was to experience the Audio Research VT80 driving three different sets of speakers I have on hand, each with a differing sensitivity. The first pair is a nifty design I recently picked up since I’ve become interested in exploring the combination of high sensitivity speakers and low powered amps. These are the Omega Speaker Systems Super Alnico Monitors (SAMs). These speakers employ a single, full-range driver per side and use no crossover. The drivers reside in fairly large cabinets for a stand-mount design, which lends the speakers a sound of authority and gusto. I think the Omegas sound awesome, especially for the price (which ranges from $1,995 USD to $2,295 USD, depending on finish), and they mate well with a wide range of amplifiers. The SAMs represent the high-efficiency solution, with a measured efficiency of 95dB. The intermediate efficiency option was my pair of Fritz Speakers Carbon 7 SEs, ($2,500 USD) which clock in at about 89dB. Finally, the low efficiency choice was my reference pair of ATC SCM19 (version 2) monitors ($4,300 USD), which measure at about 84dB efficiency. All of these speakers present relatively high-impedance loads (around eight ohms nominal) and were powered using the eight-ohm taps on the VT80.

Driving the Omega SAMs

First up was the VT80 driving the efficient single-driver Omega Super Alnico Monitors. For all intents and purposes, the 75 watts offered up by the Audio Research amp was more than sufficient (if not serious overkill) for these speakers, which can supposedly get away with being driven with as little as a single watt of quality power. I found, however, that a little extra juice wasn’t necessarily a bad thing with these Omegas, as I noticed a nice jump in dynamics, bass impact, and control. A lot of folks prefer to run the SAMs with tubes, and I must concur that the sound with the VT80 was to the right side of ravishing: The amp just seemed to coax the best out of these speakers in terms of pure tonal beauty and long-term listenability. Regardless of what amplification I have hooked up to these SAMs though, I’ve found the sound to be exceptionally involving, due at least in part to the coherence, purity of tone, and precise pacing offered up by the more-or-less point source characteristics of the full range, yet super light-weight hemp drivers I find it hard to pull myself away from these speakers during those infamous late night sessions.

J Mood.

I’ve been entranced lately listening to Wynton Marsalis’ 1985 album J Mood (LP, Columbia, digitally archived). This music is most definitely contemporary jazz as measured by its intensity, but with a nod backwards to the hard bop era (a la Miles Davis in his prime). With the Omega SAMs powered by the VT80, I was never disappointed when listening to this engaging album Wynton’s trumpet was full of tonal color and sounded just huge hanging there in the soundscape. The percussion on this album is insanely complex and fast, yet the VT80 had no trouble keeping up with the super light and lightning fast drivers in the Omega speakers; Jeff Watts’ sticks against skin were a thing of wonder to experience via the combo. Minute details previously lost or unnoticed seemingly burst from the speakers in as effortless a manner as could be imagined. I almost could have sworn I was listening to electrostatic transducers.

Power Spot.

My next selection for evaluation was something more esoteric and ethereal, an album by the modern trumpet artist Jon Hassell entitled Power Spot (LP, ECM, digitally archived). This is a hard album to categorize, as it falls somewhere along the lines of ambient, free jazz, and electronica. Central to the music here is Hassell’s oddly-muted trumpet, which often sounds more like something electronically synthesized, coupled with a driving, almost hypnotic, bass line. It’s weird music, to say the least, but after a few listenings, it somehow works. The recording is quite ethereal, leading to some crazy soundstage and imaging effects if one’s system is up to the task. Via the SAM/VT80 combo, the tonal effect is stunning with notes leaping from the drivers and then decaying away in their complex harmonic beauty. There’s also a tremendous sense of spaciousness to the recording conveyed by the VT80, letting the speakers disappear in the soundscape as sounds emanate above, in front, and behind them.

Moodswing.

Another recording which has been seeing a great deal of spin time lately is Joshua Redman’s double LP Mood Swing (Nonesuch, digitally archived). Redman’s tenor sax has a phenomenal honey-like sound that manages to take the sting and funk out of the worst possible day at work. Besides that, the album is beautifully recorded, with a nice sense of authority and spaciousness. Checking out the first cut, “Sweet Sorrow,” I hear all of the strengths offered up by the VT80 driving the Omega speakers. On show are the deep resonant tones of Redman’s horn, along with the complexities of the overtones and harmonics that go with it. I mean, this amp brings out the vibrant tonal colors that are the hallmark of the Omega SAMs in such a way that only vacuum tubes seem able to muster. Same goes for the acoustic bass, which displays an organic, yet punchy and extended tone that belies the size of the individual driver in each speaker. While not super extended like some systems can do, this is no “one-note” bass, folks, but rather an almost uncannily complex facsimile of the real thing.

While I had the Omega SAMs set up and dialed in, I figured it would be a good time to replace the Audio Research VT80 with my otherwise favorite amplification combination for these speakers, my tubed LTA MicroZOTL 2.0 as a preamp driving the excellent solid state First Watt F7 amplifier so that some direct comparisons could be made. Differences were readily apparent, starting with the ability to flesh out tonal color, an area where the Audio Research amp strode out ahead of the First Watt. Put simply, the VT80 just sounded more like a tube amp (big surprise…) in terms of its ability to capture the complex harmonics of instruments such as Wynton Marsalis’ trumpet and Joshua Redman’s saxophone. It’s not that the LTA/First Watt combination came up terribly short here, it’s just that the VT80 really aced that particular part of the exam. I was also somewhat surprised that the Audio Research amp provided deeper, rounder, and more extended bass than the solid state F7, though this could be in part due to the increased power reserves offered by the VT80. On the flip side, the F7’s bass was somewhat tighter and more controlled. Both amplifier setups did a spectacular job with soundstage and imaging, allowing the soundscape to detach itself wholly from the speaker boxes, while carving out each individual instrument in its own space. On several cuts from the Jon Hassell album, I’d actually give the nod to the LTA/First Watt setup, as the soundstage actually produced the illusion of not only extending well beyond the speakers laterally, but wrapping back around toward my listening position, thus giving me the experience of being “engulfed” by swirling waves of sound.

Driving the Fritz Carbon 7 SEs

Driving the Fritz Carbon 7 SE speakers, the Audio Research VT80 sounded about as pretty as can be. These are forgiving speakers to begin with, and sound good with almost any type of amplification in my experience. The VT80 made these speakers sound quite mellow and easy on the ears, as in presenting the kind of sound a person could listen to all day without stress or strain. Compared to the Omega SAMs, the Fritzes could perhaps be a bit reticent when driven with tubes, but whether this situation is a detriment or not really depends on the preferences of the listener. I personally prefer a bit more “jump,” especially in the area of microdynamics such as I heard with the VT80 driving the SAMs, but I also know I can get more of this quality from the Carbon 7s when I use them with a good solid state amp that resides tonally either to the slightly warm side of neutral or into neutrality itself. For instance, I’ve gotten excellent results from this speaker using the Pass Labs INT-60 and the Benchmark AHB2 amplifiers.

With that observation out of the way, however, I still contend that there’s a lot to like about the Carbon 7/Audio Research matchup. It’s like listening to music with a slight happy buzz on, as leading edge transients are a bit dulled, while the complex harmonics that give instruments their full tonal character are retained. Again, the effect is quite pleasing, and something I think a lot of listeners will like it. Soundstage and imaging are also quite impressive, though I don’t think that the individual instrument images are quite as precisely carved out in three-dimensional space as they were with the Omega SAM speakers. I can’t say for sure, but this superb $8,000 USD amplifier might actually be stretching the limits of what the $2,500 USD Carbon 7s can deliver, something I can’t say I’ve achieved before with any other amplifier.

Joshua Redman’s sax was quite luscious from a tonal perspective, though I thought it sounded smaller and more recessed in the soundstage than it did through the Omega speakers There may have been just a little harmonic color missing as well, but I didn’t find that to detract from my listening enjoyment In fact, through the Carbon 7 speakers, I thoroughly enjoyed listening to the Marsalis, Hassell, and Redman albums all the way through, with no issues of strain or listening fatigue whatsoever.

Driving the ATC SCM19 (version 2) monitors

Finally up for evaluation with the VT80 were the most challenging set of speakers on hand: the less-than-efficient ATC SCM19s. I wasn’t quite sure how successful this pairing would be, as most folks I’ve heard about like to run these speakers with relatively powerful solid-state amplifiers. For example, the speakers really lit up with the 250 watts-per-channel Pass Labs XA250.8, but fared less well with Pass’s lower powered INT-60 amp. However, the audio gods can throw some funny and unexpected tricks at you, as my favourite setup with these speakers (at reasonable volume levels, anyway) is the combination of the LTA MicroZOTL preamp with the puny 20 watt per channel First Watt F7. Go figure…

From my first listen, I could tell right away that I was really going to dig this combination. There’s something quite special about the coupling of the Audio Research amp’s vacuum tube goodness with the ATCs’ super clean, zero bullshit, studio monitor presentation that really tickled my fancy. I really had no idea that a tube amp could make these speakers sing like they do! All of the clarity and resolution I’m used to with the ATCs was there, but with more bloom and body through the midrange …. I found this effect a welcome addition, as it seemed to add some realistic texture and life to the music that drew me in to the point that it was hard to pull myself back out into reality. The VT80 also complemented the somewhat overly tight and sometimes dry bass these speakers can exhibit, again adding some substance and body to that part of the spectrum as well. Even so, I didn’t note any real bass overhang or bloat; notes seemed just as tight, but just more “there.” Treble was also remarkably sweet, yet extended, with just a bit of mellowing of the SCM19’s super-accurate tweeter What’s not to like?

Coming back to Joshua Redman, I found that the horn’s sound just drew me in and grabbed hold of my mind, body, and spirit Coming back to reality? What? Why bother? I’m here now….

Parting Thoughts

75 watts of power.

The Audio Research VT80, a so-called “entry level” amp, costs a cool eight grand. That’s a lot of scratch for a regular guy like me. Would I call it a good deal?  Well, in the grand scheme of things, when you think about its sonic goodness, build quality, and pedigree, especially when compared with certain other gear at or near the same price, I’d say yes, it does represent good value. Nothing these days is really what you could call an investment, but this amp gets close, at least in terms of its longevity, probable resale value, and the amount of enjoyment its owner is going to get out of it.

Perhaps the best way for me to sum the equation is like this: the Audio Research VT80 sounds to me what (at least in my mind) a really top-notch modern tube amp ought to sound like. At the risk of the cliche, there’s a certain magic inherent to “vacuum tube sound” that even the best solid state designs just can’t quite capture, and it has something to do with tonal purity, body, dimension, and texture, all of which combine to involve me more deeply in the listening experience. Doggone it, if I’m going to spend big money on a vacuum tube amp, I want it to sound like one. And the Audio Research VT80 achieves that goal — in delicious, delightful spades.

Very highly recommended.

Meow.