Tube Power Amp Reviews

I'm in favor of saving energy, and I'm all for reducing the unnecessary wear on tubes that occurs when an amp is left on without music being played. The MC275LE's Power Save feature, which turns off the power when there's been no input signal for 30 minutes, addresses these concerns. However, like most tube electronics, the MC275LE needs to warm up before it sounds its best, and the automatic turn-off interrupts the warm-up process. After about an hour of warm-up the sound was more open and dynamic, with a better sense of space. So, unfortunately, Power Save, while good for the environment and saving you money, can exact a sonic penalty. If you use Power Save and your listening is frequently interrupted by 30-minute periods of playing no music, then some of the time you're not hearing the amplifier at its best. If you own the MC275LE, you may decide that the benefits of Power Save outweigh the sonic cost. However, if you're doing in-store comparisons with other amplifiers, you must make sure that the MC275LE has been on for at least an hour. The difference is not negligible.

So, with the MC275LE warmed up, what did it sound like? I'll start with the speaker that was my initial impetus for wanting to review the MC275LE.

MartinLogan Montis
Those who've read my review of the MartinLogan Montis are familiar with this part of the story. Very simply: Of the amplifiers I had on hand, the best match with these speakers was the MC275LE. It had all the dynamics and very nearly all the bass of the Simaudio, and it beat the solid-state amp in natural harmonic quality. The PrimaLuna was more comparable in its presentation of harmonics, but the MC275LE was more transparent, presenting fine detail with greater clarity and delicacy. The MC275LE's claimed 75Wpc is 3dB less than the Simaudio's 150Wpc, and that could make a difference in some systems—but in my 16' by 14' by 7.5' listening room, the MC275LE was able to drive the 91dB-sensitive Montises to higher-than-comfortable levels (peaks of 103dB, C-weighted) without signs of distress from amp or speakers. If I owned the Montises, or a pair of one of MartinLogan's other electrostatic hybrids, the MC275LE would be the first amplifier I'd consider pairing with them.

Avantgarde Uno Nano
With this horn hybrid speaker, the first hurdle for an amplifier to pass is noise. The Avantgarde's +100dB sensitivity allows any noise, hum, or buzz produced by an amplifier (or anything else in the system) to be heard. The PrimaLuna, Audiopax, and Simaudio are actually quite good in this respect, but some otherwise-admirable amplifiers, such as the Conrad-Johnson M-125, had more audible noise than is ideal.

The MC275LE was one of the quietest amplifiers I've used to drive the Avantgardes. With the volume control at the normal listening level and nothing playing, I had to be within a foot or so of the midrange horn before I could hear any noise (a soft shh) from the speaker, and even that disappeared when the preamp volume was muted. The Mac's claimed signal/noise ratio of 105dB is real!

Before the arrival of the MC275LE, the most synergistic amplifier I'd used with the Uno Nanos was the Audiopax Model 88 Mk.II. There's something about this combination that allows presentation of musically important detail while minimizing sonic characteristics that represent faults in the recording and reproduction process.

The MC275LE combined with the Avantgardes in a way that just about matched the Audiopax's ability to maximize musical detail while minimizing electronic artifacts. The Simaudio, while matching the MC275LE in lack of noise and overall clarity, evinced a slight "electronic" haze that was apparent in direct comparisons. (In all comparisons, I routinely match volume as closely as possible. Where the match is not as close as I'd like, I "bracket" the volume settings so that neither amplifier has a consistent volume advantage.) The PrimaLuna, while overall very listenable, lacked the delicate fine detail the MC275LE was able to communicate.

Wharfedale Jade 7
This is what you might call a "real world" speaker: a floorstanding four-way, no powered subwoofer, and selling for $4200/pair. The Jade 7's sensitivity is 88dB, which is about average—a bit lower than the MartinLogan's, and much lower than the Avantgarde's.

I'll postpone discussion of the Wharfedale's sound until my review—as I write this, the Jade 7s are still going through what I've been advised is a rather long and necessary break-in period. But I've heard enough to be able to say that pairing the Wharfedales with the MC275LE was another excellent match. I had to turn the volume control higher to get the same levels as with the MartinLogan and, especially, the Avantgarde, but the MC275LE's 75Wpc had no trouble driving the Jade 7s to levels higher than I would normally find comfortable. Watch this space for the full review.

The Sound of McIntosh
No doubt about it: The McIntosh MC275LE is a great amplifier. Whatever speakers it drove, the MC275LE had a sound that I felt retained all that's positive about tube sound, while avoiding those things that deviate from accuracy.

In his review of the Version V MC275, Fred Kaplan noted two areas in which he felt the amp's performance suffered in comparison to his reference Krell FBI: deep bass and high treble. I can appreciate that the Krell, rated at 300Wpc and with a frequency response extending down to 0.1Hz, was able to produce better bass from Fred's Revel Ultima Studio2s. Tube amps are not at their best in the low bass. However, I found the MC275LE to be quite satisfactory in this respect with the speakers I had on hand. Bass performance is known to depend on the amplifier's damping factor, and the change in factor from 14 to 22 between the V.V and V.VI would be expected to improve the amplifier's control over the excursion of the speaker cones.

The MC275LE's bass was never bloated or sluggish in the manner of "classic" tube amps. Without having a V.V available for comparison, I can't say whether the V.VI had better bass, but its bass was as deep as the speakers were capable of reproducing, and bass drums had the proper weight and tautness. The MC275LE's bass was as good as or better than that of any tube amp I've had in my system, and very close to that of the solid-state, 150Wpc, Simaudio Moon Evolution W-7.

Much the same argument can be made about the MC275LE's high treble. V.V is specified as having a top end extending to 70kHz, whereas V.VI goes up to 100kHz. Although both of those frequencies are well above the range of human hearing, this sort of expansion of bandwidth is often reported to produce a more open, more "airy"-sounding top end, and that was consistent with my observations. Depending, of course, on the speakers (and other associated components), the treble of the MC275LE was clean, clear, not overly soft, but not overbright, either. The top-to-bottom tonal balance seemed to me just about ideal.

One area of the MC275LE's performance that particularly impressed me was a sense of rhythmic drive. This is not a sonic characteristic that I normally associate with tube electronics, and yet, time and time again, playing a variety of familiar records (mostly CDs, but also some LPs) through the MC275LE, I was made unusually aware of the rhythm and rhythmic variations. Frank Sinatra really knew how to swing, and though I've appreciated this aspect of his artistry in the past, listening to Come Fly With Me (CD, Capitol CDP 7 48469 2), I repeatedly found myself admiring how he and the band were partners, allowing the pace to vary in a natural, nonmechanical way.

Bottom Line
In producing the 50th Anniversary Limited Edition of an amplifier that was already considered a classic, McIntosh could have taken the easy route of just upgrading the cosmetics and functionality, and perhaps replacing capacitors and resistors with higher-spec components—they would still have sold boatloads of them. But that wasn't good enough for the McIntosh engineers. Every aspect of the MC275's design and construction was examined, and several technical improvements made. The MC275LE is simply a wonderful-sounding amplifier, able to bring out the best from a wide range of loudspeakers, and its price represents good value in today's market. Production of the MC275LE is limited to 275 for the US and Canada (not limited for the rest of the world). I don't know how many of those units are still available, but that number has just been reduced by one: I'm buying the review sample.