June 2010

Audio Research VSi60 Integrated Amplifier

The world is full of 50Wpc integrated amplifiers, and though the list shrinks somewhat when you’d like those 50W to come from vacuum tubes, that still leaves dozens of choices. Why so many? For most moderately sized rooms with modestly efficient speakers, 50Wpc is plenty of power. Making an amplifier -- particularly a tube amp -- with greater power output not only gets more expensive, but the added circuit complexity can negatively affect the amp’s sonic performance. The convenience and economy of an integrated amplifier make sense to a lot of people, me included.

I’ve heard a number of Audio Research Corporation components at dealers and in the homes of fellow audiophiles, but I’d never had any of their gear in my own system. When ARC released their new VSi60 integrated amplifier, it was time for me to do so.

Description

The VSi60 is based on the circuitry of ARC’s VS60 amplifier, with a little more gain -- a total of 32.5dB. The control circuitry is what you’ll find in any reference-level preamplifier: microprocessor-controlled relays and very short signal paths. Combining these two functions into a single chassis saves space and cost -- the virtues of all integrated amplifiers. Like all other ARC components, the VSi60 is hand-built in Plymouth, Minnesota, by skilled technicians using high-quality parts and heavy circuit boards. At $3995 USD, the VSi60 isn’t cheap, but it’s a reasonable way to enter into the world of ARC.

The VSi60 looks like a tube amp but is technically a hybrid; it has a JFET input stage. Each channel employs two 6550 output tubes in push-pull configuration, and one 6H30 driver tube. The circuit employs less than 7dB of negative feedback. The specifications list an output of 50W but no load. We can assume that this value is for 8 ohms, but tube amps vary little in power output with changing impedance. The VSi60 has a wide power bandwidth, from 1Hz to 80kHz. Its input sensitivity is 0.47V, with a maximum input of 3.5V, which should be appropriate for almost all partnering equipment. The total harmonic distortion is rated at a mere 0.05% at 1W, this rising to a still modest 1.5% at 50W. Overall, the specs suggest a competently designed amplifier that should work well in the real world.

The VSi60 measures 14”W x 8”H x 16”D and weighs a hefty 35 pounds. The top plate, through which protrude the tubes, transformers, and capacitors, is of milled aluminum. A cage-like cover that protects the tubes is available at an extra cost. The front panel is available in black or silver. While I can’t speak of the materials used in the silver version, the black front panel is made of a cheap-feeling plastic, making the VSi60 one of the ugliest audio components I’ve ever seen. It reminds me of a piece of laboratory equipment from the 1980s.

On the front panel are buttons for Power, Mute, Source selection, Volume, and Stereo/Mono -- this last feature is useful for early stereo recordings wherein half of the ensemble is in each channel. All of these functions are duplicated on the remote control. Also on the front are LEDs that indicate source, volume, mute status, and stereo/mono.

Around back are five pairs of single-ended inputs and a full-range mono subwoofer output. There is also an IEC socket for the included detachable power cord. Speaker connections are by way of heavy, gold-plated, five-way binding posts with taps for 4 and 8 ohms. While many tube amps force you to hold the probes of your multimeter to contact points while adjusting the bias current, ARC’s designers have thoughtfully included terminals on the rear panel that provide a secure connection while you’re biasing the output tubes.

Setup

Sometimes, setting up a tube amplifier can be a bit of a chore, but it wasn’t with the VSi60. After unpacking the amp from its shipping carton, one simply places each tube in its numbered socket. It’s important to pay attention to the numbering; ARC sets the bias current at the factory. The obsessive audiophile -- which describes all of us -- will undoubtedly want to recheck the bias, but should be sure to wait until the amp has come to a stable operating temperature in order to get a valid reading. The only thing then left to do is to find a sturdy shelf on your equipment rack and connect your sources and speakers.

I connected the VSi60 to my Esoteric MG-10 speakers using 8’ lengths of DH Labs Q-10 speaker cable. The MG-10 has a nominal impedance of 6 ohms, so I tried both the VSi60’s 4- and 8-ohm taps. I quickly settled on 8 ohms; in this configuration, the amplifier exhibited significantly better control in the bass and an overall cleaner sound. Which taps will be right for your system will depend not only on the nominal impedance of your speakers, but also on how low the impedance dips throughout their frequency response.

Sound

The first thing I heard after powering up the VSi60 was . . . nothing. The amplifier’s output is muted for the first 30 seconds to prevent any potentially damaging clicks or pops from making it to your speakers. This warmup time also prevents you from running a signal through the tubes before they’re ready, thus prolonging tube life. After giving the VSi60 about half an hour to reach thermal equilibrium, I still heard almost nothing. In fact, with the ARC’s volume turned all the way up and my ear to a speaker, I heard only a slight hiss and an even fainter hum. In terms of absolute noise floor, I’ve heard very few tube amps that rival the VSi60’s performance, and none that beat it. Actually, I’ve heard a number of very pricey solid-state amplifiers that aren’t as quiet as the VSi60. While a low noise floor is not the only thing to look for in an amp, it is critically important. Any noise produced by the amplifier, whether hiss or hum, will necessarily mask fine details of the music. So even before it had played its first note, the VSi60 had impressed me -- and raised my expectations for what I was about to hear.

The cleanness of the VSi60’s sound with no signal present carried through when I began to play music. Instruments and voices emerged from a black background, allowing me to hear fine details. In some of the quieter passages from Lera Auerbach’s 24 Preludes for Violin and Piano, performed by Vadim Gluzman and Angela Yoffe (CD, BIS 1242), I could discern both the attack and the release of the hammer for each note in the piano’s higher registers. With RCA Living Stereo recordings of the Chicago Symphony, I could hear every creak of chair and turn of page. With closely miked vocal recordings such as “I’ll Never Be the Same,” from Diana Krall’s Temptation (CD, Verve B0001995-32), I could clearly hear the singer’s every breath and tongue movement. On “You Don’t Have to Say You Love Me,” from Shelby Lynne’s Just a Little Lovin’ (CD, Lost Highway B0009789-02), I could distinguish the pick of each guitar string and the sliding of fingers across those strings.

I’ve heard some people scoff at such details as musically irrelevant. In most cases, these people are making excuses for equipment that is incapable of reproducing them. But high-end audio reproduction is about not only musical but experiential relevance. When I go to a concert, unless I’m seated at the rear of a very large hall, I hear these sorts of details. Hearing them from my audio system better mimics the live event. Furthermore, whether or not I want to hear such details, if they are present in the recording, the system should faithfully reproduce them. If you value these sorts of details, the VSi60 will not disappoint you.

You may be concerned about the ability of a 50Wpc tube amp to reproduce clean, powerful bass, but you needn’t be. The title track of the Shelby Lynne CD has, in my opinion, too much bass, and the VSi60 delivered all of it. But while the level of the bass guitar is a little high, it is clean and articulate, and the VSi60 reproduced each note with a defined beginning and end surrounding a meaty center with plenty of volume and tone. My Esoteric monitors go down only to 41Hz, but late in my listening to the ARC I took delivery of a pair of Verity Audio Finns, which can go a few cycles lower while moving appreciably more air. The Finns let me delve a little deeper -- pun intended -- into the VSi60’s bass performance. The bass drum in the second movement of Mahler’s Symphony 4, with Bernard Haitink and the Royal Concertgebouw Orchestra (SACD/CD, RCO Live 7003), goes far lower than any bass guitar, but it, too, was reproduced by the VSi60 with depth, weight, and a definite shape to the sound.

Of course, bass performance isn’t only about weight and depth. In order for an amplifier to have good pace, rhythm, and timing, bass notes must be well articulated. While I’ve yet to hear a tube amp that can deliver the vise-like grip of a good solid-state amp, the VSi60 always sounded well in control. Most jazz recordings get their rhythmic drive from a walking bass line; any flabbiness in the reproduction of the low end can disrupt the forward momentum of the piece. Listening through the ARC, I never had any doubt as to where the beat lay. In fact, the VSi60 impressed me in every aspect of its bass performance -- something that can rarely be said of a moderately powered tube amplifier. Some readers might point out that part of the VSi60’s signal path is solid-state, but transistors are employed only in the input stage. Bass power and control primarily depend on an amplifier’s output stage. Whatever the reason, the VSi60’s bass performance should satisfy all but the most ardent bass fiends, and the largest, most power-hungry speakers.

Perhaps you’ve heard the phrase “the magic is in the midrange.” Whether or not you consider the VSi60’s midrange to be magical will depend on the type of magic you seek. If you look to a tube amp to provide a lush, syrupy sound, then the VSi60 is not for you -- you’d be better served by an amplifier employing single-ended triodes. If, on the other hand, magic for you means neutrality, then you’re in luck. That’s not to say that I found the VSi60 incapable of reproducing voices in a beguiling manner, but that it didn’t emphasize them, or add to them other distortions that changed their character. As both a reviewer and a listener, my preference is for a system that maintains a recording’s integrity. I’ve always felt that, if you want to add a particular color to the sound, a better way to do it is with judicious speaker selection. If you wish to make a change in the future, it’s much easier to match a colored speaker with a neutral amplifier than to match a colored speaker with a colored amplifier. For me, the VSi60 had the right kind of magic. Although not syrupy, its midrange was liquid in the way that only tubes and the best solid-state amps can manage.

Moving up the audioband, the highest octave was smooth and reasonably extended, though perhaps without the last little bit of air. The VSi60 did nothing to cover up the flaws in poor recordings, but good recordings were never harsh or strident. On the Auerbach disc, high notes in the violin never took on the hard quality that they can with some other amplifiers. It was only when playing back some SACDs that I felt the VSi60 could be slightly bettered. The triangle in the Mahler recording seemed to lack that last little bit of shimmer, and the violins in the exposed passages could have had a little more harmonic texture. Your ability to discern these differences will be highly dependent on your speakers and source material. If you must have that last little bit of high-frequency extension beyond what the VSi60 offers, you’d best be prepared to pay for it, whether in dollars or in lower power output.

Soundstaging was another of the VSi60’s strengths. Voices and instruments were clearly laid out from left to right, and in many layers from front to back. The sonic vista extended slightly beyond my speakers and a number of feet behind them. Not only was the soundstage well proportioned, it was rock solid. Images didn’t wander, and instruments and voices had a tangible presence. What’s more, the dimension of the soundstage varied from recording to recording. While I could have wished for a bit more voluminous-sounding halls with some large orchestral recordings, I could clearly hear distinctions among different recording venues.

Comparison

My own reference integrated amplifier for the past few years has been the GRAAF GM-50, which has the same 50Wpc power rating as the Audio Research VSi60. The GRAAF’s output stages are designed around two KT88 tubes per channel. Like the 6550, the KT88 is a beam tetrode, albeit with higher power dissipation.

There are two notable design differences between the two amplifiers. First, the GRAAF’s signal path is entirely tubed. Second, the GRAAF is fully balanced from input to output. At $7500, the GRAAF also costs 50% more than the ARC. What, if anything, do you get for that extra money?

One thing you get is a little more noise. Though the GRAAF is exceptionally quiet for a tube amplifier, whether it’s the VSi60’s solid-state input stage or some other design choice, the ARC was a little quieter with no signal playing. Both amps exhibited similarly low levels of hiss, but there was a little more power-supply hum through the GM-50. Whether or not the GRAAF’s fully balanced circuits will matter to you will mostly depend on whether you have any source with a balanced output. Although the basic character of the sound didn’t change, I noticed a slight improvement in fine detail when I connected the Ayre Acoustics C-5xe^MP universal player to the GRAAF via the Ayre’s balanced vs. its single-ended output. This balanced connection let me hear a modest amount further into the recordings with the GM-50 than with the VSi60. For example, the decays of notes from stringed instruments, whether plucked or bowed, were a little longer and more natural. When I connected the Ayre to the GRAAF via the Ayre’s single-ended outputs, the difference, though still there, shrank considerably. The GM-50 also seemed a bit more extended in the very highest frequencies versus the VSi60. By that, I don’t mean that they were brighter; in fact, the GRAAF seemed to have a slightly darker sound overall than the ARC. This greater HF extension gave voices and instruments a little more harmonic texture through the GRAAF. Both amplifiers delivered similarly liquid yet tonally neutral midranges.

The other differences in the sounds of these two amplifiers were matters of preference, not absolutes. Although both delivered very good bass extension, the ARC had a leaner, punchier bass, while the GRAAF exhibited a touch more bloom and a slightly greater sense of depth. With regard to soundstaging, and given the right recording, the GM-50 can produce a truly cavernous aural landscape; the VSi60 countered with slightly firmer boundaries. If you spend much of your time listening to big orchestral music, the scale of the GRAAF’s sound might be more your style. But if you listen to a lot of rock, the ARC’s physicality may better suit you. But either integrated could deliver a fulfilling musical experience, regardless of musical genre.

Conclusion

The Audio Research VSi60 is not inexpensive at $3995, but its sound and build qualities are commensurate with its price. When you consider that it’s designed and built in the US by a company with a long and solid reputation, that price seems even more reasonable. Its strengths are those more often encountered in a solid-state amplifier: a surprisingly low noise floor, tonal neutrality, and exceptional bass performance. Yet it retains the liquidity and smooth upper frequencies of tubes. If an integrated amplifier makes as much sense to you as it does to many audiophiles, the VSi60 would make a great center around which to build your system.

. . . S. Andrea Sundaram
andreas@soundstagenetwork.com