Tube Power Amp Reviews

When I reviewed VTL's 25W Tiny Triodes in April 1991, I found them to be incredibly fun little suckers to play with, but got frustrated with their inability to drive my Spica Angeluses to reasonable levels with most of my recordings. I loved what I was hearing, but there wasn't nearly enough of it! As it turns out, John Atkinson was listening; not just to my plea, but also to the new VTL Compact 160 monoblocks in preparation for a full review. However, while all this was going on, David Manley decided that the power-supply voltages in the 160 weren't beefy enough to exploit his new KT90 output tubes; back the amps went for a transformerectomy.

Most reviewers look for a "hook" or angle of some kind when it comes time to write a review. After all, how many ways are there to get excited about audio equipment? Kathleen and I like to focus on the human side of the High End. So it was with some amusement that I watched the obstacles swirl around what I thought would be a fairly straightforward review of the Vacuum Tube Logic MB-1250 Wotan monoblock power amplifier. My thought was to return from single-ended to push-pull with a bang! I'll say...

It all began at the January 1996 WCES, where I found my shorts positively welded to the listening chair during a memorable musical blast at VTL. Luke Manley and his extreme audiophile wife Bea had a good thing going and they knew it. People were talking. "Did you hear those monster two-storey VTLs on the Alón Vs?"

Stop me if you've heard this one: Back in the early 1990s, just after the fall of the Soviet Union, I debated professor of music engineering and magazine columnist Ken Pohlmann on a talk show on the CBS radio network. The subject was analog sound vs digital sound, but I guess when Pohlmann felt I was getting the upper hand, he felt he needed to play the tube card. Derisively, he said, "I bet you're one of those tube guys, too, aren't you?" Before I could open my mouth, he continued: "You know, the Soviet Union's military gear, including the MIG fighters, ran on tube electronics, and look what happened to them!"

Not only does the venerable vacuum tube refuse to lie down and die, as everyone predicted when audio went solid-state; it continues to deliver better performance than anyone had imagined it could. Only a few years ago, we could characterize "the tube sound" as being sweet but soft at the high end, rich but loose in the midbass, deficient in deep bass, and bright and forward, usually with excellent reproduction of depth. Since then, we've seen the introduction of what might almost be called a new generation of tube amplifiers, which rival solid-state units in those areas where tubes used to have weaknesses, but have given up little of the tube's sonic strengths.

How much power do you really need? What does it do for you, anyway? Even before the single-ended renaissance, the prevailing wisdom was that you really didn't need that much power. When I had a pair of Met 7 speakers, even the "1 watt" indicator LED was hardly ever lit. Ditto for my time with a Threshold Stasis Two—all those cool power-indicator LEDs just sat there dark. Besides, everyone knows that power can be had only at tremendous cost, both monetary and in terms of other performance attributes.

Big tube amplifiers were once scary monsters reserved for those who didn't mind heavy maintenance, careful tweaking, and the occasional explosion. Blown tubes required replacing, preferably with pricey matched pairs, then biasing with a voltmeter. Optimal sonic performance required regular bias monitoring and adjusting, and because of current surges on startup, you had to choose between leaving the heat-producing monoliths on, or turning them on and off for each listening session, thus shortening the life of the tubes.

"More power!!!"