Tube Power Amp Reviews

The Audio Research D-160B has been heavily modified since the D-160A, and uses the same technology as the D-70, D-115, and D-250. It embodies William Z. Johnson's latest transformer and power supply designs, his latest choice of capacitors and resistors, and the same independent regulation of screens, drivers, and front end. D-160s and D-160As can be converted to D-160Bs for $1500.

It says something for the state of technology that, after a quarter of a century, there still is no authoritative explanation for why so many high-end audiophiles prefer tubes. Tubes not only refuse to die, they seem to be coming back. The number of US and British firms making high-end tube equipment is growing steadily, and an increasing number of comparatively low-priced units are becoming available. There is a large market in renovated or used tube equipment—I must confess to owning a converted McIntosh MR-71 tuner—and there are even some indications that tube manufacturers are improving their reliability, although getting good tubes remains a problem.

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?"

The VTL MB-450 series began life in the late 1980s as the Deluxe 300, a pair of which I once owned. Over the years the basic design has been improved and modified, in the forms of the MB-450 (1996) and the MB-450 Series II (which I reviewed in January 2008). The tube complement remains the same: eight 6550s in the push-pull output stage, a 12AT7 input tube, and a 12BH7 driver. Into a 5 ohm load, the MB-450 III is claimed to produce 425W in tetrode mode or 225W in triode, from 20Hz to 20kHz.

It's been a while since I've had a classic amplifier in my system, and McIntosh Laboratory's MC275 is as classic as they come. Introduced in 1961 as the "powerhouse" of that era's newfangled stereo tube amps (two 75W amplifiers in one chassis!), the MC275 retained its position as the amplifier to own—challenged only, perhaps, by Marantz and a few others—until 1970, when it fell prey to the widespread wisdom that transistors were king and tubes were dead, and the model was discontinued. The MC275 briefly returned in 1993, in a limited "Commemorative" edition to honor the late Gordon Gow, longtime president and chief designer of McIntosh Labs. To everyone's surprise, that edition sold well, and McIntosh, gingerly at first, crept back into the tube business.

I hate audio shows. All those manufacturers and retailers desperately demonstrating their products, knowing how impossible it is to do them justice in a hotel room. They might be saying, "It has gold-plated circuit boards and unobtainium binding posts," but all I hear is Please love it, please love it, oh puhleeze . . .

Two audiophile buddies of mine both own Rogue Audio M-150 monoblocks. I'd always been impressed with not only the sound quality of the M-150, but also its price. For $4495/pair, I thought my friends got a whole lotta amp for notta lotta dough. In this day and age, it's a rare and wonderful thing to get a pair of monoblocks, made in the US by a real audio company, that give you 150Wpc of tube power for under $5000. When Rogue came out with an update of the M-150, the M-180 ($5495), I thought it might be a good subject for my first full review in Stereophile. John Atkinson thought so too. I also thought it would be interesting to compare the M-180 with the very tube-like and almost identically priced Pass Labs XA30.5 two-channel amplifier ($5500), a sample of which I had on hand. (see my Follow-Uphttp://www.stereophile.com/solidpoweramps/pass_labs_xa305_power_amplifi…; in August 2009).