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Positive Feedback ISSUE 46
november/december 2009



Mc501 amplifiers

as reviewed by Marshall Nack







Kharma Exquisite-Midi.

mbl 5011 preamplifier and mbl 8011 AM monoblocks. ASR Basis Exclusive phono preamp.

VYGER Baltic M turntable, Shelter Harmony cartridge, mbl 1521A transport, mbl 1511F DAC.

Interconnects are Tara Labs The 0.8, Kubala-Sosna Emotion, Kondo, and Kharma Enigma. Digital cables are Tara Labs The 0.8, Kubala-Sosna Emotion. Speaker wires are TARA Labs Omega and 0.8, Kubala-Sosna Emotion, and Harmonix. AC power cords are Tara Labs The One, Kubala-Sosna Emotion, and Harmonix.

TAOC Rack and TITE-35S component footers, Walker Audio Tuning Discs and Valid Points for LP turntable, Harmonix RFA-78i Room Tuning Discs, RFS-66ZX Tuning Feet, CORE Designs amp stands, Acoustic System Resonators, Marigo VTS Dots, Argent Room Lenses, Echo Buster & Sonex acoustic panels, TARA Labs PM/2 and IDAT power conditioners, and Ensemble Mega PowerPoint outlet strips.


I unpacked the McIntosh Mc501 mono amps—you'd better have a buddy help you do this—and placed them on the carpet next to my speakers. The location was chosen more for photo op reasons than anything else. My, they do look gorgeous over there, sporting the classic McIntosh exterior features, beefy and over-built with a decidedly masculine appeal. I cannibalized the wires off my current amp and fired them up and, as they were McIntosh's demo pair, they didn't need much burn-in time. In short order, I could tell just how good they were. Going back to my mbl 8011 AM monoblocks seemed a remote option at this point.

And then we went on vacation.

How I Spent My Summer Vacation

This summer, the fourth in a row, we went to the Ottawa International Chamber Music Festival in Ontario, Canada, which bills itself the largest of its kind in the world. The festival is like Woodstock for the greybeards, expanded to two weeks. We attended 19 concerts in seven days.

The very first program we heard was the Leipzig String Quartet performing Haydn's The Seven Last Words of Christ. Man, are they good! I had never heard the Leipzig before and this would prove to be the high point of the entire week.

Back home, I came upon the Leipzigers' recording of that same Haydn opus (MDG 907 1550-6) in my local used record store, cheaply priced because no one knows about them here. I already had three versions of this work in my CD collection by other noteworthy groups: the period instrument Quatuor Mosaïques, the Talich and the Emerson. I did the comparison—we'll get to that in a minute. Suffice to say, the Leipzig is an exciting discovery.

I'm going to use The Seven Last Words of Christ to compare handling of intimately scaled music between the Mc501s and my reference mbl 8011 AM monoblocks. I consider the 8011s the pack leader in this price territory (MSRP $14,300). Judging the Mc501s against them sets the bar quite high.

mbl 8010 AMs

Through the 8011s, the aspects of the Leipzigers live performance that caught my attention in Ottawa were evident in my living room. Three things in particular:

Dynamic range is tempered. The Leipzig occasionally reach up to an f, but most of the time they play at a level below mezzo forté. Then, to add drama, they play more quietly.

They have uncommonly rich timbre.

The ensemble's voice is very unified. The members agree on an interpretation and that's how they play it.

The Leipzigers play with maximum understatement, unmatched taste and superlative ensemble. Their music making is about tone colors. I've heard this playing style on older recordings, but never in live performance. I assumed it was a relic of bygone days, an old-world European thing that was extinct. This is the legendary "speaking with one voice" style.

The 8011s are especially good at bringing out color and nuance. When comparing the four Haydn CDs they allowed me to hear how each string quartet approached the piece. Of the four, the Talich come closest to the Leipzig's style, with similar rich timbre. They fell short, however, in terms of technical finesse. The Mosaïques was a flat-out disappointment. Neither their voices nor their interpretation were unified, plus the CD had balance issues. The Emerson was marvelously in sync interpretively, but hyped dynamic markings and lacked the richness of tone. The Emerson typifies the contemporary ideal: bold dynamics and a very focused tone, emphasizing the fundamental note value. They tend to play loud and, to make a contrast, play louder still.


Moving over to the Mc501s, tonal balance became quite a bit darker and much more full-bodied, especially in the treble, so that it better matched the quality of frequencies below it. The Mc501s have a midrange and treble character one associates with valves, in terms of frequency integration, body, overall sweetness of tone and the slightly short-changed treble. Don't get alarmed. Treble extension is satisfying; it just doesn't reach up as much, or as often, as many solid-state amps.

Bass performance is another story: it may be warm and full, but you'll never get this kind of power and control from valves—or from most solid state for that matter. The bottom end is superb.

At the tail end of the note, the Mc501s stop. Period. You hear it most noticeably in the bass where the low frequencies are now lined up with the rest. And at the start, the Mc501s arrive unheralded in a waveform approximating a right angle. The contrast between signal and silence registers. How the note starts and stops are two of the bigger differences between the amps.

The mbl has a bit of a scoop in the leading edge and doesn't control the tail as well. Hence, the mbl imparts a soft, dreamy quality. The difference between signal and silence is played down; it is not filled by blackness. Focus is not as tight.

In part because of this and because it is tonally lighter, the mbl has a buoyancy, the sound lofts, it breathes. The Mc501s doesn't have this buoyancy, despite its livelier dynamics. Maybe that's because there is always low-frequency energy present—this amp has extraordinary weight. The weightiness and the rigid control over the signal keep images rooted to terra firma.

Neither amp has any grain or etch to speak of. In other regards, dynamics and soundstaging were on par with the 8011 given this small-scale material.

The funny thing was, I was not getting the nuances that make the Leipzigers special through the Mc501s. When I compared them to the Talich, the Mc501s gave me an overall style difference, but the innermost detail and timbral differences were only hinted at. There wasn't as much grit, I wasn't hearing the bow or the vibrato, and I wasn't hearing their timbral synchronicity. The Mc501s low-level resolution is not only not at the level of the 8011s; it is a bit less than you would expect at this price point.


Now let's move to the other end of the spectrum and compare power music such as Mussorgsky's Night on Bald Mountain, with Paavo Jarvi and the Cincinnati Symphony Orchestra (Telarc SACD-60705).


Through the mbl, the stage is densely populated. Image outlines are somewhat indistinct and spread out. It has the same soft quality as the Haydn, with scooping transients and lingering trails. Dynamics are great—when the bass drum is smacked, you feel it.


It's just that the Mc501s smack the drum harder. Now you hear the up side of the low frequency energy being ever-present. These amps have the kind of weight and authority that we're all searching for, but is normally only to be found in much more expensive products. Their dynamic range can be scary. They can start objects in the room shaking and generate pressure against your chest. In truth, my 8011s sound tame by comparison.

The Mc501s transient has that square form and the tail stops on a dime. The familiar sound of the 8011s started coherently, but never finished together. The bass would linger past the rest, with consequent smearing. I was pretty sure this was caused by the 8011s not sufficiently controlling the speaker woofers. I developed this notion when I auditioned the one-up mbl 9007 monoblocks, with their 440 watts per channel into 8Ω and 30 amperes of current (vs. the 210 watts and 23 amps of the 8011s). The 9007s brought my speakers to another level. (Now I'm having second thoughts about this analysis, since the 8011s also display this character with quiet program material. I think it more likely that's how they're voiced.)

The shocking news is the Mc501s dynamics are every bit as good as the mbl 9007s (MSRP $33,000). Amazing, at one third of the price! No doubt this is a reflection of their 500 watts into and incredible 100 amperes of current. Of one thing I'm sure: It's been a long time since the dynamic capability of my speakers has been realized—actually, three years ago, when the mbl 9007s departed. With my speakers, those watts/current numbers make a huge difference.

An amp can overdo its control, becoming tight and uninvolving. While the Mc501s have a very strong will, it is embedded within a cluster of synergistic traits that skirt that description. I wouldn't call them analytical.

Usually the assumption is power and finesse are inversely related; the higher the first, the coarser the sound. Well, not in this case. The Mc501 is one sweet sounding amp. Listen to the last track on the Mussorgsky CD, the Prelude to Khovanshchina. It contains some wonderfully romantic writing for woodwinds and orchestra. The Mc501s don't short change the beautiful tone of the wind section.

Dynamic power

The Mc501s are outstanding through a wide swath of performance attributes, but if I had to choose just one, I would go with dynamic power.

Listen to Dizzy Gillespie's Big 4 (Analogue Productions APJ024, a heavy weight reissue of the Pablo LP from 1974). Track one, Tanga, goes on in a soft groove for a long intro. The upright, the bass drum and the guitar are doing their thing, all in the low register, and it sets your foot a-tapping.


All of a sudden the Diz opens up with one of his signature high-octane leaps into the treble register. It pops out of the speakers and I practically fall off the couch!

You have to experience those multi-octave jumps to know what I mean. To hear the amps effortlessly straddle those peaks is a marvel. It's possible to perceive this as larger than life and the images as over-sized. Yes, it certainly appears that way in relation to amps I'm familiar with. But it is certainly impressive..

Setup and Design

For serious listening, I moved the Mc501s onto a pair of CORE Designs Amp Stands. As for wires, the Mc501s have wide latitude—their strong signature minimizes differences. I used the TARA Labs The One power cords and Kubala-Sosna Emotion speaker cables and interconnects. That's it for tweaking. I didn't have to spend much time tinkering to get great sound from them.

McIntosh put plenty of patented design goodies in the Mc501s, like the Power Guard circuit, which limits output harmonic distortion, and the Sentry Monitor protection circuit. The comprehensive manual details these and more.

It's worth talking about their Autoformer circuit. There are numerous approaches to loudspeaker design. From one to the next, speakers place varying demands in front of the amplifier. The thing is, a given amp can be optimized for just one—unless it has an Autoformer. The Autoformer in the Mc501s optimizes impedance and other electrical characteristics for the 2, 4 and 8-ohm speaker taps. (I believe this is why the Mc501s spec 500 watts output into any impedance..) This keeps your speaker happy regardless of its nominal impedance and the Mc501s running cool while performing to the max. You might be surprised to learn that these megawatt, high current monoblocks never got more than warm to the touch, and only on the transformer casing. The Autoformer, a big, black box visually identical to the transformer box, sits next to it. Until you know about it, you'd think there were two transformers on each chassis.

I used the gold-plated 4-ohm binding posts with my Kharma speakers.

The only thing I would change is the orientation of the power receptacle. It looks up, so your power cord has to look down. Most components plug in from the side, which is easier when you're dealing with massive, audiophile-grade PCs.


McIntosh Labs has forged a reputation over many decades for reliability and good sound done straight up, if not competing at SOTA levels. The current house sound continues to evolve within that vein. Based on the solid-state Mc501s and brief exposure to the tubed Mc2301 monoblocks, I'd venture many people will be shocked at where its arrived—it's a knockout.

I can say with a fair degree of assurance you will not find better dynamic performance at anywhere near the Mc501s price point. The Macs are authoritative in this important capacity. And the rest of the audio scorecard is also very impressive. Without question, the Mc501 deserves high ranking among the contenders in the Class A stratum. The Mc501s will make 99% of audiophiles delirious.

Going into this review I thought I had a clear upgrade path from my mbl 8011 AMs, another top contender at this price point. (Actually, the mbls are now $14.3K, well above the Mc501s at $11K.) But I soon found myself in a quandary.

While I would have to give the Mc501s the nod as far as overall grades on the scorecard, what complicated things was their resolution of low-level details came in below expectations.

The choice is yours: it depends on what you like to listen to and what you value most. If your taste runs to extroverted fare, you won't find better than the Mc501s. Conversely, if you prefer intimacy and subtlety, you will want the mbl 8011 AMs. Marshal Nack

Mc501 mono amplifier
Retail: $11,000 pair

McIntosh Laboratory, Inc.
Binghamton, NY
web address: