VTL MB-1250 Wotan monoblock amplifier Page 2

Hmmm...I tried two or three wire changes, but it was obvious the cablage was not at fault. Not wanting to imagine it, I finally wired up Forsell's hulking The Statement and our own Jadis JA-200s. Both evinced not a whit of fuzz at either frequency extreme. Alas, all roads seemed to lead to Wotan. Frustrated with all the schlepping and hooking, I called Luke. "Oh yeah...that might be a problem with the value of the cap in the return leg of the feedback loop." Now he tells me!

So back he came. I'd go to work in the morning, he'd be there. I'd come back home in the evening, he'd still be there, surrounded by electronic effluvia. Nope, it wasn't the cap in the feedback loop. (Luke personally installs each set of Wotans and dials them in for the client's speaker, so don't start yelling "special reviewer treatment" just yet.)

After three days he gave up. He was eyeing the Avalon Ascents suspiciously, but their relatively benign impedance curve had never proven a challenge before. (They do like power, however.) Luke postulated that his ultra–wide-bandwidth amps might be ringing the metal-dome tweeter at its "oil-can" breakup frequency, but this didn't explain the fuzzy-dice bass. Weird...the amps had shown no sign of breakup on the big Alóns at CES, or on an Ascent-based system he'd dragged yet another pair of Wotans to after returning home.

We agreed to set the monsters aside, and he'd pick them up just before HI-FI '96 at the Waldorf. (New Yorkers say "Waldorf" instead of the whole "=Astoria" schmeer...) The plan was to leave us another of three pairs of Wotans he'd be using at the Show. That sounded reasonable, although "setting aside" his amps was hardly a trivial matter. "One, two, three—unghhhh!"

Finally the great day arrived, and we were once again With Wotan. What would happen? What else could happen? In fact, they sounded just fine, even as I assaulted them with murderously high levels of signal. The windows rattled, the front door bulged and flew open, but there was no fuzz and not a trace of breakup.

Bye-bye, Luke...we'll be in touch.

Not so fast...
But nothing's that easy. We were accumulating hours on this second pair when another minor disaster occurred. The two-stage turn-on switch from the first pair were absent from this replacement set. And so, almost inevitably, after months of working well enough, one of the switches fused itself but good on turn-on, and wouldn't turn off.

I pulled the plug and telephoned VTL once again, concerned about reviewer-frying arcs from the Wotan if I was so imprudent as to jam the connector back into the amp. This call resulted in a quick visit from one Ernest Pirog, VTL owner, booster, and all-around audio fanatic. (His amps and Alón Phalanx speakers are all hard-wired, for example.) Basically, Ernest saved the day by making available a quickly-cobbled-up version of the "Pirog Power Switch," as employed in his own VTL/Manley–amped system.

"Some power switch," I thought grumpily as I laid out the constituent parts on the carpet: two Variacs and a pair of industrial-strength GE Double Throw Safety Switch boxes. This setup allows the amps to be left cooking at around 80V on the Variacs when not in use, and to be engaged by "throwing" the spring-loaded lever home (BAM!!) to the bottom of the two "on" positions. I had to remember to drop the Variacs back to about 30V when the amps were "on the wall" so that, when reengaged, they wouldn't blow their fuses. I shut the Variacs off and disconnected them during so-called "critical" listening sessions.

When I did listen, I levered the arm at the side of each box up to the central "off" position for a moment, then dropped them back down the other way to engage the second switch in the box, powered from the wall. (Each box was wired with a common ground between the two supplies.) I used audiophile power cords from the amps to the switches: either Essential Sound Products' The Essence or Synergistic Research AC Master Couplers.

My Official Position: Yes, during the review period Kathleen and I wound up jumping through hoops to get it done. There will certainly be those of you who will become engorged with mirth, imagining that no one in their right mind would go through so much just to listen to a pair of amps. It is rather a lot to ask.

But if you imagine that no one but a reviewer (and not every one at that) would go through all this before chucking the amps off a pier into the East River, recall that Ernest built these elaborate switchboxes for himself. In fact, when I balked initially at the idea of using the Variacs, he insisted (you know how audiophiles can insist) that the sound of his rig was much improved by reduced-voltage simmering when not playing music. I have to admit, he was absolutely right. Startlingly so.

In fact, I'm may ask Ernest to make us up a set of switchboxes and Variacs with audiophile-approved internal wiring. When considering this entire matter, and after regaining control of yourself, remember that the production-spec two-position turn-on switch addresses this problem.

Anyway, that's how we used 'em. Imagine.

The second pair of Wotans, obviously up to snuff, sounded much more like a wide-bandwidth design of contemporary specification than had the first. As we ran them in, I flipped back and forth between tetrode and triode, and settled on the latter with no misgivings whatsoever.

Yes, the bass was better, deeper, tighter in tetrode—1250W per side, after all. It was also marginally more transparent and focused, but it was in the highs that the sound took a dive—a bit too much grain for my tastes. (Although far less objectionable than some other tetrode or ultralinear designs I've heard.) Triode is where it's at, and with 600W on tap, headroom wouldn't be a problem.

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Vacuum Tube Logic
4774 Murietta St., Suite 9
Chino, CA 91710
(909) 627-5944
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