VAC Avatar integrated amplifier Chip Stern follows up
When we left the VAC Avatar back in the April 2000 issue, it was being put through its paces on Thomas J. Norton's test bench. Tom had already observed curious behavior from the right channel's 4 ohm output transformer tap in Ultralinear mode when, just as he concluded his basic measurements, the Avatar gave up the ghost. The preamp section was dead, the right channel worked only intermittently, and the amp shut down if he tried to get more than 5W from the right channel in Ultralinear or Triode mode. While the left channel worked fine in both modes, it did so only when fed from the Home Theater Direct input. Thus, the "Measurements" Sidebar of the review concluded with an incomplete assessment of this lush-sounding integrated amp.
As reported in my original review, I'd experienced intermittent problems with output and driver tubes and a series of blown fuses. John Atkinson suspected a wiring or tube problem connected with the right-channel UL/Triode switching function and the right-channel output transformer's 4 ohm output tap.
When the Avatar was returned to VAC, designer Kevin Hayes gave it a once-over before returning it to us for this Follow-Up. He wrote to Stereophile: "Our examination of Chip's review sample showed one bad output tube and the demise of the associated screen resistor. These two items have been replaced. No other fault was found. No other change has been made. This is the state in which the amplifier will be returned for Follow-Up.
"Now, how could the screen resistor fail? A runaway tube or an arc in an output tube can damage the screen resistor (so would a badly mis-biased tube, but such was not the case here). However, it is exceedingly rare—albeit not impossible—for a single such event to take out the resistor. This is because the part is a wire-wound resistor, specifically chosen for its ability to withstand high-voltage pulses. It is therefore likely that the EL34 was defective for a period of time, causing the protection fuse to blow more than once, each time weakening the screen resistor a bit."
Ah, yes: The butler did it. On receiving the Avatar back for another go-round, I was especially conscious of the behavior of the four EL34 output tubes, and kept an eye out for any hints that one might be wavering.
On the VAC Avatar, tube biasing is accomplished by removing the milled faceplate, pressing a button for each tube, and using a rotary trim pot to center at midnight the arrow on the circular, illuminated, Marantz-style meter in the middle of the front panel. I anticipated some initial drift from spec as a result of shipping, and sure enough, during initial setup and bias, tube #3 seemed to be still settling in, exhibiting some noise artifacts as if it were clearing its throat or burning off some oxide effluvia.
That first evening I returned again and again to the bias controls, as the behavior of this tube seemingly affected that of the others. I left the Avatar on overnight, and by late next morning it had settled in. I tapped tube #3 with a pencil eraser, and there was no evidence of any untoward microphonic effects, nor was there with any of the other tubes. The bias, too, had settled in; it remained stable over the next few weeks, requiring little tweaking. During that time I left it running for long periods, after which I would power the unit down and turn it on again. I experienced no blown fuses or extraneous tube noise, although the character of the Avatar's actual noise floor with the volume control set above the midnight setting, with no signal, in both the CD and phono modes, did give me pause.
The background noise grew louder as I advanced the control past midnight toward full power, sounding in CD mode like a grounding hum, and in phono mode like hashy surf. However, given the Avatar's high voltage gain—TJN measured a maximum of 35dB—11 o'clock was the loudest I ever cranked the system, and that was plenty loud, plenty clear, and safely below the audible noise range. Nevertheless, that sense of aural combustion—of a revved-up race car running right up to the edge of its performance limits—made me reconsider my automotive metaphors. While the Avatar's appearance projected the elegance of a Rolls-Royce, its sound had the nitro-methane burning guts of a souped-up Pontiac GTO.
But the Avatar was no hot-rod jalopy with the front-side passenger seat ripped out; there was still a surfeit of rich Corinthian leather in the interior, and she comes with all the appointments. Last time out, I teamed the Avatar with the 4 ohm Celestion A3 speakers and went back and forth between Triode and Ultralinear mode. This time I drove the Joseph Audio RM7si's with the Avatar in 60W Ultralinear mode, which, I concluded, was the Avatar's strong suit. Last time, I ran 20' biwire lengths of Straight Wire Serenade speaker cable; this time, I used 8' biwires composed of Synergistic Research Resolution Reference Mk.II for the bass, and SR's Designer's Reference for the highs (above 2kHz for the two-way Josephs). Instead of the Straight Wire Serenade interconnects, I employed 15' of Synergistic Research Resolution Reference Mk.II interconnects (with Discrete Shielding only) from the Sony SCD-777ES SACD player to the CD inputs. Finally, I ran a Synergistic Research Designer's Reference2 AC Master Coupler into a JPS Power AC Outlet Center (with a 20'/8-gauge run to my dedicated line).
The sound was every bit as intoxicating and involving as I recall from my first cohabitation with the Avatar: a sweet, rich, open presentation with plenty of air and juicy midrange detailing. I listened to a number of sources, but for convenience's sake returned for final evaluations to Not Two, Not One (ECM 1670), a magnificent and varied recital featuring pianist Paul Bley, bassist Gary Peacock, and drummer Paul Motian. While my usual Mesa Tigris in its 1/3-triode/2/3-pentode mode (28W) has extraordinary bass slam, tonal warmth and dynamic immediacy, I was struck anew by the weight and speed of the Avatar's bass resolution, and its natural tonal balance from top to bottom. On the dancing "Fig Foot," the Avatar kept everything in tempo, crisply delineating the finer aspects of Peacock's tone without neglecting rhythm and pacing.
The overall resolution and soundstaging were quite good; I experienced a very strong sense of image placement, and of the holographic shape of the drum set and piano within the soundstage. Bley's piano and Motian's drums not only sounded vivid and lifelike, they "looked" like three-dimensional images. I loved the air and detailing of Motian's shimmering, sizzling cymbals, and when he brought up his bass drum for a big accent during his solo, it spoke with a perfect combination of timbre and physical immediacy, without any murky colorations. It spoke like a bell.
I'm still quite taken with the sound signature of the Avatar. Some folks might find it a bit on the bright side, and, when pushed past its limits, it did have a touch of strain in the upper midrange. I thought it sounded splendid with the brilliant, ultra-revealing RM7si, but I suggest that when you audition it, you begin with some warm-sounding speakers and work your way up to the more analytical. Still, I didn't find it hard, but lively and musical; if you don't need that much power or bass control, you might be more than content to run it at 28W triode.
The Avatar costs roughly a grand more than the Manley Stingray or the Mesa Tigris, but it also has a very nice phono section. While I still wish VAC had provided a true preamp out rather than that Home Theater Direct mode (for integrating with a 5.1-channel surround system), if you go for that distinctive sound signature, you'll go for the whole jizzombie. The Avatar enlivened my experience of music.—Chip Stern