Audiopax Model Eighty Eight monoblock power amplifier Page 3

I found the controls quite fiddly to operate, the LED display changing with the slightest turn of the knob. The bias levels indicated by the LEDs tended to drift after the nominal warmup period, so that while the bias levels may have been adjusted an hour after turn-on to read 11/3, a few hours later they could be at 11/2. Having tweaked the bias to read 11/3 near the end of a late-night listening session, it was not unusual for me to find the next day, after a half-hour warmup, that the bias levels were off by one or more LED indicators. I can't say that the sonic effect of the bias drift was all that noticeable, but the Audiopax Eighty Eight will give audiophiles of the obsessive-compulsive sort an outlet for their predilection.

The Model Eighty Eights came with what looked like generic power cords. When I asked Avantgarde's Jim Smith whether these were more special than they looked, he confirmed that they were just ordinary power cords, and that it was expected that most users at this level will choose their own specialty aftermarket cords. I used a pair of PS Audio Lab Cables, which I've found to work well with other high-end amplifiers. These were plugged into a PS Audio Ultimate Outlet power-line conditioner, the combination producing a reduction of noise over the stock power cords plugged directly into the wall.

In my review of the Air Tight ATM-211, I noted improvements from use of Vistek Aurios MSB Pro supports under the amplifier and from placing Duende Criature damper rings on the small driver tubes. I tried these tweaks with the Model Eighty Eights, and, as with the Air Tight amp, heard improvements in transient clarity. (The KT88s are too close to each other to be fitted with damper rings.)

Another tweak had nothing to do with the Audiopax as such, but did have a significant beneficial effect on the sound of the system as a whole. It came courtesy Geoff Poor, director of sales for Balanced Audio Technology and a fellow Avantgarde owner. An ardent audiophile who's never reluctant to share his experience, Geoff told me that he'd found the Shunyata Research Taipan power cable to be the best for use with the Avantgarde powered subs. I got hold of a pair and swapped them for the TARA Labs Decade power cables that I'd been using, and heard a surprising improvement in the clarity and solidity of the bass.

With all these tweaks in place, I was ready to do some serious listening. And then it happened: intermittent noise in the right channel, like paper being torn or crumpled—the type of noise I associate with tube problems. Tapping the KT88s seemed to confirm the diagnosis, and I e-mailed Jim Smith to report the problem. He immediately dispatched another set of tubes, which I installed, and everything was fine—for a day or two. The noise then returned, in the same channel. This time, I swapped the tubes between the channels, and both channels were quiet for a while. The noise then recurred, again in the right channel. Tapping one of the KT88s changed the noise, but my initial conclusion was clearly wrong: the problem was not with the tube itself but the tube socket or something connected to it. Another e-mail to Jim Smith, who told me that Eduardo de Lima was planning a trip to the US the following week and would just move up the date of his visit, with a side trip to see me and fix the problem.

That's just how it worked out. De Lima came, opened up the amplifier, and said that some of the innards had apparently shifted due to some rough handling in shipping, with one resistor lead intermittently touching another wire when the amplifier got hot, shunting it to ground. He simply bent one of the wires so that they were not as close, and the noise was gone (footnote 1).

The final tweak came about as a result of a conversation with de Lima during his visit. I asked him to elaborate on his claim that amplifier distortion can cancel out speaker distortion, which he did with considerable eloquence. Then, almost as an afterthought, he suggested that my system would probably sound better if I reversed the connection between the speaker and the amplifier from the way I had it, maintaining the signal's absolute polarity by using the Perpetual Technologies P-3A's polarity-reversal button (footnote 2). I did as he suggested and heard a very significant improvement in openness and sense of space.

Journey's End
When I try to get a handle on the sound of a component, my approach at first is always holistic rather than an attempt to focus on any specific sonic attribute. Does the sound resemble live music? Does the component allow the music played through it to reach me at an emotional level? Can I listen for long periods without feeling like I want to do something else?

US distributor: Avantgarde-USA
6445 Calamar Drive
Cumming, GA 30040
(770) 777-2095