McIntosh MC501 monoblock power amplifier
When I was in my early teens, I studied classical and theater organ for several years. My teacher, Elaine, and her husband were, to put it mildly, fanatical about their hobbies. They spent four months slowly moving a moth-eaten, mouse-infested, and utterly non-functional 1925 Wurlitzer pipe organ into their basement from its original residence in an Iowa theater. Whatever happened to that Wurlitzer, I do not know; what captivated me lived upstairs: a three-manual Rodgers Trio theater organ and the most incredible stereo system I'd ever seen. The highlight of my week was to go over and play that beautiful Rodgers for an hour—at least until the day Elaine introduced me to some new music by playing it on that complicated, fascinating-looking, but as yet unheard system. On that day, my interest in audio was awakened and a lifelong obsession was born. It's fair to say that without having heard that system, I would not be writing these words in 2004.
Elaine and Gary's stereo system was a thing of wonder and awe, and every piece of electronics in it was from McIntosh: a glitzy tubed tuner-preamplifier and two 50W tube monoblocks, all driving a pair of Altec-Lansing Voice of the Theater speakers—the ones with the fancy woodwork, not the black, theater-ready boxes (footnote 1). Hearing Virgil Fox played over that system was like hearing the voice of God. It was then that the light was turned on. I had never in my life thought that the sound of music could come that vividly into a home, and even my skeptical parents were impressed enough to eventually let me pick out my first stereo system and buy it for me (footnote 2).
For years, until I encountered the High End in the mid-1980s, McIntosh remained my Holy Grail—the Best of the Best, the Brand to Aspire To. After all, it was Mac gear that had anchored the best system I'd ever heard, so it must be the best. Even the notoriously picky Grateful Dead used nothing but McIntosh amps in their most ambitious PA systems. Who could argue with those credentials?
As I immersed myself in the High End, first as a hobbyist and eventually as a reviewer, I learned that "real" High-Enders considered McIntosh to be passé and something of a carriage-trade brand—still well made, supremely reliable, and cool-looking in their retro way, but nowhere near the state of the art in terms of modern, high-performance sound. Bankers and doctors bought McIntosh, not "serious" audiophiles. So ran the conventional wisdom.
A voice from my past
Beginning in the mid-1990s, something began percolating in Binghamton, New York (footnote 3). It began slowly, when McIntosh reissued the classic tube C22 preamp and MC275 power amplifier. The runaway success of those Sidney Corderman-designed pieces seemed to light a fire under the McIntosh design staff. While expanding into a remarkably comprehensive range of components for home theater and whole-house systems, two-channel audio of the highest quality—both tube and solid-state—once again became a top priority for the venerable company. The MC501 ($4100 each) is the latest and most powerful expression of McIntosh's solid-state thinking.
I rediscovered McIntosh via the unlikely route of home theater. Though I'm not an enthusiast, I appreciate the fun of home theater, and over a number of years, the most consistently enjoyable home theater setups I experienced were in McIntosh's rooms at various Consumer Electronics Shows. Unlike most manufacturers, Mac always made a point of first demonstrating that their HT systems were excellent music systems, before moving on to the plane crashes and dinosaurs. At last year's Home Entertainment Show in San Francisco, McIntosh had a great-sounding two-channel room which I visited repeatedly, as if to convince myself that a Mac system could sound that good. The megapowered MC501 monoblocks caught my ear, and Mac's Sally Goff was perfectly happy to send me a pair, along with the new C200 two-chassis control center (which I will review in the October issue). So, would my first audio love still curl my toes some 30 years later? I couldn't wait to find out.
The design of the MC501 is straightforward and extremely burly. Not only is the amp capable of delivering 500W into any load between 8 and 2 ohms, it's also rated to deliver more than 100 amperes of output current. It seems exceedingly unlikely that there is a speaker that the MC501 could not drive.
McIntosh's overarching paradigm is maximum linearity and minimal distortion. To this end, the linearity of each gain stage is maximized before the application of negative feedback, and all transistors are selected, according to McIntosh, to have "nearly constant current gain over the entire current range they must cover." The output transistors "have matched uniform current gain, high current bandwidth product and large active region safe operating area." According to the manual, "an automatic tracking bias system completely eliminates any trace of crossover distortion," and "precision metal-film resistors and low-dielectric absorption film capacitors are used in all critical circuit locations."
The '501's circuitry is described as Double-Balanced Push-Pull. Each half of the amplifier is fully balanced from input to output. I've never seen each phase of a signal rendered in balanced configuration before, but there you go. The four output signals of the two balanced circuits are all reunited at the Autoformer coupling transformer.
The most unusual feature of McIntosh solid-state amps is, of course, that Autoformer. The basis of the patented Autoformer concept is that transistors, like tubes, perform best into an optimum load. According to Mac, "this optimum load may vary considerably from what a loudspeaker requires...a power amplifier connected to a load that is lower than optimum causes more output current to flow, which results in extra heat being generated in the power output stage." The Autoformer, by creating an optimal match between speaker and output stage, allows the amp to work within its comfort range virtually all of the time. No performance sacrifices are necessary, says McIntosh, as the Autoformer's frequency response "exceeds that of the output circuit itself, and extends well beyond the audible range."
Footnote 1: I even remember the turntable—a Rondine Rek-O-Kut with a weird cantilevered arm in which the Pickering cartridge was the only pivoting part.—Paul Bolin
Footnote 2: My first proper stereo system was a Sansui AU-222 integrated amplifier, largish Goodmans bookshelf speakers (they had to be good because they were English, even if they weren't the more expensive Wharfedales I so shamelessly coveted), and a PE turntable with a Shure M47 cartridge. I was 15 and was prouder of it than I could have imagined. I wish I had it back, if only for the memories.—Paul Bolin
Footnote 3: As has been extensively chronicled, primarily by the estimable Mr. Tellig in "Sam's Space" over the last 10 years.—Paul Bolin