In other respects, I would say the MC 501 sounds as though it were voiced with a very good tube power amplifier as a reference. It isn’t the most transparent amplifier, because instruments seem to emerge from an ever-so-light fog. This, for some, will resemble the sound of live music. In the lower frequencies, the MC 501 delivers a firm foundation, though the midbass lacks some of the control one might wish for. Dynamically, the MC 501 is on the polite side of things. I am not sure, but it almost seemed that MC 501 couldn’t completely get a grip on the MBLs. No nasty sounds were ever emitted, but the MC 501 never came fully alive in my setup, either.
I then switched in the Classé CA-M400s. My first thought about these monoblocks was that they sounded rich, warm, and relaxed. Like the McIntosh amplifiers, the CA-M400s sound smooth, though by comparison they don’t quite have the sense of continuousness that the MC 501s deliver. At the same time, the CA-M400s seemed very happy with the MBLs dynamically, sounding powerful, rhythmic, and controlled. After extended listening, I came to think that these amplifiers offered plenty of transparency and high-frequency delineation, but it was as though their lower distortion in the treble made them sound a bit darker at first. Later on, this simply seemed natural and unforced.
I am a big fan of the Mahler symphonies. These are large and sometimes densely orchestrated pieces that can put components to the test. With the Classé, as the sound ramps up (which in Mahler is pretty frequently) it felt less pinched and strained than it did with some other amps, and yet at the same time I could clearly hear what was going on at the instrumental level. My only reservation was that the Classé seemed a little reserved, particularly in the high frequencies.
At this point, I was excited to try the Audio Research 300.2. The McIntosh and the Classé sound different, but not dramatically so. I figured a completely different amplifier technology would shake things up, and I was right. The Audio Research immediately sounded more dynamic than the other amps in this group. Drums and plucked instruments like guitars really stood out in the mix with this amplifier, and bass was very well defined. I also appreciated the sense of instrumental delineation that the Audio Research provided, although by comparison I realized I couldn’t really hear anything that I couldn’t hear on the Classé. It just seemed that some instruments had a brighter light shining on them. This brilliance came without a sense of stridency on, say, violin. Very impressive.
The troubling thing about the 300.2 is that I didn’t find it to sound completely natural. Something about the way it treats the leading edge of transients seemed slightly too caffeinated. Exciting and even involving, but not quite right.
I tried Neil Young’s Prairie Wind [Reprise] and even though this CD has a very warm mix, on the 300.2 the sibilance of Neil’s voice was exaggerated. Acoustic guitar sometimes was rendered as a bit jangly sounding, as if it were being played on an instrument with a metal resonator. At the same time, some reissues of analog recordings sounded about as alive as I’ve ever heard them, without sounding harsh or cold. Whatever problem the 300.2 has, it seems to occur in a very narrow band and is reduced dramatically when the amp has had 24 or 48 hours to warm up. Tri- Path claims that their modules adapt to the characteristics of specific transistors, so maybe this long warm-up period is part of the technology.
I should mention the Musical Fidelity kW 750, even though it wasn’t under test per se. In one sense, the kW 750 can be summed up by its amazing performance on piano. More than any of the other amplifiers, the kW sounds right on solo piano. Listener after listener remarked on the uncanny way in which piano seemed tonally and dynamically right. Those of you who have listened to live piano and then to recordings will know that piano is quite difficult to reproduce. This makes sense: The piano has a very wide frequency range and is extremely dynamic. I came to think of the Musical Fidelity amplifier as quintessentially well balanced. It isn’t the most dynamic, or the most transparent, nor does it have the best bass, but it does almost everything very well, with the result that it sounds good on many different types of music.
At this point in the review process, I started thinking that all four amplifiers were really good: intelligently designed by people with a real sensitivity to music, but with different viewpoints about what constitutes the ideal. From this vantage, amplifier design has reached such a high state of development that you can tweak the sound of your system by choosing the right amplifier and the unfortunate side effects will be pretty small. That’s nice because many audiophiles, whether they like to admit it or not, are interested in choosing amplifiers to tune their systems. It is a fact of life that with all the hard work and good intentions we put into putting our systems together, inevitably something is “off” and we’d like to correct it. You can try this with any element in the listening chain, of course. However, after months of listening to these amplifiers, I would say that power amplifiers lend themselves well to this sort of adjustment, provided that the tuning you need is in certain areas.