Whirr...whirr...whirr...ka-BLAM! The bike didn't so much start as explode into life. Though I wore my best unimpressed New Yawker's face, I was keenly aware of its sound as I ducked an errant cab and finished sauntering across Sixth. The big twin settled quickly into its uniquely throaty, lumpy idle, and I instinctively waited for Biker Boy (lucky bastard) to give it the gas. Thonka-thonka-thonka blat ka-BOOM chatter-chatter-thonka-thonka... I could almost feel the vibration between my legs, the wind in my hair. Hey, it was windy!

Would Biker Boy accelerate past me as he blasted down 17th Street? Or turn up Sixth? The clutch took up the slack, and The Great American Icon turned the corner and roared up the Avenue of the Americas. Damn.

But I wasn't envious. I, too, had a Great American Icon—a pair of them, in fact—waiting for me in my listening room, warmed up and ready to rumble: the McIntosh MC1201 solid-state monoblocks, 1200Wpc, with the biggest power meters you ever saw this side-a Milwaukee.

Edifice rex
Like a Harley, each McIntosh MC1201 monoblock is a huge physical presence, a big hunka iron in anyone's language: 147 gut-busting pounds of stainless-steel chassis and beautifully finished, black-shrouded transformers and heatsinks. Do yourself a big favor and let your dealer install them. You're the one paying the long booty—why should you have to schlep?

The MC1201's front panel is dominated by a huge blue backlit Output Wattmeter under glass—plastic could warp, according to McIntosh's Larry Fish. The ever-affable Mr. Fish, VP of product planning (he worked his way up to VP/chief engineer in his 27 years with the company) is quite proud of the analog meters, which are handbuilt in the UK and were originally designed for automobile test systems. How apropos.

The meter is an audiophile big deal, as explained rather elaborately in the Product Preview I received from McIntosh. An amplifier's power output (in watts) is determined by multiplying its output voltage (E) by its output current (I): EI=W. However, the output meters on some amps are actually voltmeters; output current is not taken into consideration, the company patiently explains. Even though these indicators may be calibrated in watts, they're based on the "patently false notion" that all speakers have a fixed impedance regardless of frequency.

For a specific output voltage, McIntosh continues, the current varies inversely to the speaker's impedance. If the impedance is lower, the output current and power are higher. "Since McIntosh cannot control other manufacturers' speakers, we decided to provide extra output current to drive these mismatched low impedances and to indicate the real output power required to drive them. Therefore the meter circuit in the MC1201 electronically measures both voltage and current, multiplies them, and displays the real output power in watts."

The meter uses a circuit that accelerates the pointer movement. When the pointer reaches its peak excursion, "it pauses only long enough for the human eye to perceive its position, then drops." Fish proudly asserted that the pointer's operation is almost 10 times as fast as a professional VU meter. Another feature of this stupendously large meter is its ability to respond "95% full scale to a single-cycle tone burst at 2kHz." What you see is what you get!

Although the meter's primary output calibration is from 12mW to 1200W, there are smaller 2400W and 4800W indicator positions to the far right! Impressive. "The MC1201 cannot reach this power level continuously; however, it is possible for short-interval peaks to considerably exceed the 1200W continuous rating." When I read this, I had a brief vision of clamping the front brake, cracking the throttle, and smokin' the rear tire! For the record, I never got either amp anywhere near its indicated full-power output when driving the sensitive (92dB) JMlab Utopia loudspeakers. I think I nudged 120W during a particularly enthusiastic listening session late one night, but more could not have been asked.

Lower left on the front panel, a large but easy-turning switch changes the meter to Watts, Watts Hold, and Lights Off operation. In Watts Hold, the needle locks to the highest power peak in any sequence, the reading held until a higher peak passes. If no greater peak occurs, the indicator slowly returns to its rest position at a decay rate of 6dB/minute. In Lights Off mode, the meter functions as normal, with the back-lighting turned off. (Don't worry—you still get the cool, green McIntosh logos to light up your listening room.)

The Power switch has three positions: Off, Remote, and On. Off disconnects the main AC line, and Remote is used when the amplifier is turned on by remote control. (You'll need a connection between one of the Mac preamplifiers' Power Control Out and the Power Control In on the rear of the MC1201 to carry the 5V trigger signal.) The On position bypasses the remote control and powers the beast up.

Balanced connections are made at the switch-selectable XLR input, which is rather individualistic in not using the universal locking-type XLR connector that snaps the fitting into place. I had no trouble with that, but it did catch my attention. I think it's the small details that define an audiophile design, and there lie the differences in most stark relief. In my opinion. A pair of standard RCA connectors are provided for unbalanced inputs.

The IEC mains-in connector is set horizontally on the left rear of the chassis; some of the larger audiophile power cords I used rose in wide, stiff arcs over the amps before snaking their ways to the AC outlets.

The imposing faceplate is nicely set off with a pair of what McIntosh describes as extruded aluminum anodized handles in "champagne gold." They look like matte silver to me, and are set off nicely against the big, shiny chassis and the hulking black upper structure. Classic McIntosh.

The MC1201 costs $7500 each. (Larry Fish was chuckling about a customer waiting to upgrade the half-dozen MC1000s in his home-theater system with a sextet of 1201s.) Of course, McIntosh makes speakers designed to take full power from these huge amps. The loquacious Mr. Fish then told me that their People's Republic of China dealer had set up—on stage in a concert hall—a triamped system with a pair of McIntosh XR290 loudspeakers powered by six MC1000s, and sold tickets! He said it was a successful event.

Design Philosophy
McIntosh's goal for the MC1201 was that its every stage of voltage or current amplification would be as linear as possible. To accomplish this, they used the following techniques.

First, "each transistor is selected to have nearly constant current gain (Beta) over the entire range of currents at which the transistor must operate." The load impedance presented to each amplification stage is as uniform as possible for all signal levels. The input impedance of stages is increased and "linearized where possible by using emitter degeneration." Resistors and capacitors in the signal path are carefully selected to have "exceedingly low voltage coefficients—low change of resistance or reactance with applied voltage." Precision metal-film resistors and low-dielectric-absorption film capacitors are used in all critical circuit locations. Output transistors have matched uniform current gain, "high-current gain-bandwidth product," low output capacitance, and "a large active-region safe operating area."

According to the documentation, "These characteristics and the automatic-tracking bias system eliminate crossover distortion. The distortion graphs supplied show clearly that distortion does not increase at low power output levels." Ah-ha—I'd wondered about that. According to the estimable Mr. Fish, only the first watt or two is biased into full class-A operation.

The MC1201 is fully balanced from input to output. Two matched amplifiers operate in push-pull, with their outputs combined at the Autoformer, so each half of the amplifier contains complementary balanced circuitry. McIntosh claims that the resulting "double balanced" configuration cancels virtually all distortion, and that "this circuit is possible only with the exclusive McIntosh Output Autoformer," which provides matching for 2, 4, and 8 ohm loads.

The output transformer coupling, or Balanced Dual Core Autoformer in Mac Speak, is rarely seen with solid-state designs, and provides "low-distortion power transfer and delivers peak output current in excess of 200 amperes." The MC1201 is said to have the output-current reserve to deliver more than 5kW output on tonebursts. Of the Autoformer, McIntosh says, "There is absolutely no performance limitation. Its frequency response exceeds that of the output circuit itself, and extends well beyond the audible range." The Autoformer also protects speakers from damage in the event of amplifier failure. Should a DC component appear in the output circuit, it is shunted by the transformer and thus causes no damage to the speaker.

As laid out by McIntosh, the basic circuit is a time-honored one: two balanced stages of voltage amplification followed by three stages of current amplification. All stages are complementary balanced, as noted. This means, McIntosh points out, that the amplifying stages have less total harmonic distortion and that less negative feedback is required to achieve "ultra-low" distortion.

The signal is fed to the positive inputs of the balanced differential stages. Feedback from the amplifier outputs is applied to the inputs, and the differential amplifiers drive a balanced Darlington-connected voltage amplifier stage. The voltage amplifier's output feeds complementary Darlington driver transistors. These supply the signal to 24 complementary transistors per side for a total of 48 output transistors. Ancillary components for features such as Power Guard, Sentry Monitor, the meter, and protection circuits "interconnect with the amplifier circuits."

The power supply uses a massive toroidal transformer, full-wave bridge rectifiers, and large filter capacitors with 600 joules of storage. The four large heatsinks that bristle on the back of the chassis provide more than 2800 square inches of surface area with which to cool the power-output devices.

Power Guard and Other Sentries
I think we can all agree that an amp driven into clipping, especially a solid-state one, can sound harsh. Clipping, McIntosh explains, looks and acts like the nonmusical squarewaves produced when an amplifier is asked to put out more power than it's designed to deliver.

"When an amplifier is driven into clipping, it can deliver up to 40% harmonic and intermodulation distortion. In this mode, the sound is grossly distorted and the extra energy content of the clipped signal will damage most loudspeakers. The McIntosh Power Guard circuit protects your ears and your speakers from this kind of damage." This has been a public service announcement...Power Guard is a McIntosh design (US patent 4048573).

The Power Guard circuit is a comparator that monitors the input and output waveforms. As McIntosh explains it, normally there's no disparity between these signals, so the circuit produces no output. When the MC1201 is overdriven and a difference develops, and if that difference exceeds 0.3%, the comparator output turns on the amber Power Guard indicator. If there's a further increase in distortion, the output of the Power Guard circuit engages an attenuator at the amplifier input. Reducing the amplifier gain simply holds the amp's output to a low-distortion value. However, Power Guard operates "only when the amplifier is asked to deliver more power than it was designed to produce"—a situation that I can't imagine. I never saw any amber light go on, I can tell you that, and I played 'em loud! McIntosh claims that the Power Guard acts so fast that there are "no audible side effects and the sonic purity of the music reproduction is perfectly preserved."

The Sentry Monitor joins the Power Guard in protecting your investment. Per McIntosh, all power transistors are limited in the maximum amount of power they can handle. "The MC1201's output transistors and power supply have been designed to allow very high current flow into properly matched load impedances. If, however, a short circuit or very low value of load impedance is applied to the output of the amplifier, destructive current levels could be reached. The Sentry Monitor circuit prevents this. The circuit senses the dynamic operating time, voltage, and current of the amplifier output stage and confines it to nondestructive levels. Sentry Monitor does not limit the power output available from the amplifier."

Thermal Control over the output transistors is also in the cards. The MC1201 uses an efficient output stage biased into class-AB2. Larry Fish claims that while the MC1201 runs pretty toasty, it produces relatively little heat for the output power produced. Four large heatsinks dissipate transistor-generated heat. "Natural convection air flow is sufficient for cool operation. Should the cooling air be blocked or should the amplifier operating temperature become too high, thermal cutouts turn off the input signal to the amplifier. When the amplifier has cooled, it will automatically turn on again." Again, it never happened, and I can't imagine provoking them to do so.

Turn-on inrush current is "cushioned" by thermistors in the primary power transformer circuit; the resultant soft start eliminates stress. There's also a turn-on delay circuit that holds back amplification for about two seconds after power is applied, to prevent pops or thumps from insulting your loudspeakers.

Cardas Golden Reference interconnect and Golden Cross speaker cable work fine with harsh-sounding components as they break in, and continue to sound utterly sophisticated as the sound improves. I try stuff powered from the Power Plant and directly from the wall. It's usually a struggle to get the device under test up on the bubble of best sound. When I do, it's "Hold!" and "Let's take that shot!" I begin to write the review, tweak a little more, then go back to my familiar references to finish things out.

Like the Cary CAD-1610-SEs (reviewed in December 2000), the MC1201s were a pain in the pancreas to set up just right. First off, and most noticeable, they took more than 100 hours to break in and open up, and 200 hours had gone by before I really got into them. It was an uncomfortable start—I thought I was staring a disaster in the face. (No matter what some negative nogoodniks bleat, we always tell it like it is at Stereophile.)

Best sound was achieved without a preamp, feeding the McIntoshes from the analog outputs of the dCS Elgar Plus on a dual-AES 24-bit/192kHz datastream, primed by the dCS Purcell or the dCS 972 D/D converters via Synergistic Research Designer's Reference interconnect, and Cardas or XLO The Limited speaker cables. I had to turn the ASC Studio Traps around to face more of their absorbent surfaces directly toward the drivers than is typical around here. Otherwise, the amps could still sound a little thin, electronic, and "hi-fi" on top. I'd say this was the one sonic attribute I remained aware of that I had to "fight" for best sound—that, and a big, bloated, but powerful bass that finally firmed up into audiophile-approved territory as the hours accumulated.

Run direct, get those Studio Traps just right, and, bada-boom bada-bing, audiophile-approved super sound. But remember: Without all this attention to setup and matching, the MC1201s sounded a little acerbic in the highs. Then again, you won't buy into the McIntosh ethos and order up a pair of these $15k/pair monoblocks unless you really want them. If you do, the implication is that you'll set 'em up and match 'em properly, or at least have it done for you.

Once the amps ran in and these elements were accounted for fine-tuning the room treatments, I got the sound described below.

Loitering with Intent
The MC1201s made a BIG sound in our loft. Everything about them, from their hulking physical presence to their sound, was enjoyably larger than life. In that way, they were similar to the tubed stereo McIntosh MC2000, an amplifier I described as being a star of stage and screen itself. But the MC1201s were more Harley-Davidson Macho, more massively solid-state in how they went about making that positively huge sound. In that way, they did draw attention to themselves.

I'm talking gobs of bass, effortless power and dynamics on big, complicated transients throughout the audible frequency band, and a huge, floaty, billowing soundstage in and on which the musical narratives took place. I'm not saying the MC1201 couldn't be subtle—for 15 big ones, you have the right to demand detail and finesse, and you get it. It's just that its priorities were different. To me, the McIntosh aesthetic, build, and sound are more like the two-page Cadillac ad that's been appearing in The New Yorker—an on-track shot of Caddy's Le Mans racer with a bumper sticker that reads "My other car is an STS." That's it exactly. Think Offenhauser roadster or Briggs Cunningham, Lance Reventlow and Scarab, Carroll Shelby and Cobra, Henry Two (and his nemesis, Il Commendatore) and the Ford GT40—proper American overweight monsters built like Kelvinators!

So let's roll up our sleeves and break out the welding torch, shall we? Reproducing classic recordings is just what these amps are cut out to do, so let's begin with a terrific new XRCD from JVC, Thelonious Himself (VICJ 60170), mastered in what engineer Akira Taguchi calls "big mono." Most XRCD masterings are notable for their somewhat soft and analog-like ambience. Nothing wrong with that, especially given the MC1201's propensity to slightly brilliantize the upper registers and make them a little glitzy, like a Harley. I mean, how can you criticize it? But in the end it's unmistakable and rather blatant, if you see what I mean.

In the event, with the Studio Traps turned in just so, the sound was excellent via the dCS direct. Listening to Monk that day seemed to define the audiophile experience for me—enjoying the music, thinking about how to express the sound and feeling, the meaning of a phrase, Monk's timing, the very thoughtfulness that went into each musical expression. The piano was, according to my notes, "very full-toned, with excellent overall power response, again slightly tipped up at the top, open if not completely without edge. But edge in the sense of the true nature of a piano's strings, which are, after all, made of metal." The soundstage, and the imaging thereon, were so BIG that they carried a real sense of being there into our listening room. Not subtle, but still very enjoyable.

The stereo MJQ recording was cushy and illuminated, Milt's vibes fast and brilliant. The sound was more transparent than I'd experienced with the MC1201s before, so I had another look at the fold-out insert. It was mostly in Japanese, but when I scanned the bit of English printed there, you coulda knocked me over with a feather—it was an old Atlantic remastered with 20-bit K2 processing! I couldn't find JVC's name or logo anywhere, but K2 is what Yoshida and Taguchi have been churning out those great-sounding XRCDs with. Realizing that, it struck me how much the two recordings sounded alike, with their large, lushly painted sonic landscapes for your acoustic third eye to feast on. The tonal color and shimmer of the vibraphone once again raised the hackles on my neck.

Enjoying MJQ—and perhaps DCC's finest release, Bags Meets Wes! (GZS-1093), with Milt Jackson and Wes Montgomery—I took some notes. "Nice image padding and placement, good, very round palpability, and nice lush'n'shimmer in the lower treble as so ably struck by Bags hisself in this sublime moment of proto-late-'50s jazz, a template of sorts for all to come. Lush...lush...the lazy circling of Connie Kay's wire brushes on his snare drums rattling around like fine golden chips on a scrim of gossamer sound." It was so immediate and vibrant it gave me the shivers.

While I'm no great fan of Chausson, do yourself a favor and find Musique Français pour Clarinette & Piano (Lyrinx LYR 2195, SACD/CD hybrid, distributed by Harmonia Mundi, available through Acoustic Sounds), where you'll also find works by Saint-Saëns, Debussy, Widor, and Poulenc. During the Allegro animato of Saint-Saëns' Sonata Op.167, I noted that "the clarinet has rarely sounded so vibrant and alive, so burnished and acoustically buoyant. Like a spring day, it gave my heart joy to feel the energy of such beautiful playing on such a gorgeous-sounding CD layer. (John Atkinson currently has the Accuphase DP-100/DC-101 SACD/CD converter; I'll tell you more about the SACD layer when the Accuphase returns, which will be soon. Right, John? John?)

Debussy's Rhapsody No.1 is utterly beautiful music, wonderfully recorded, and alone worth the price of the disc. Once again, I noted a distinct and natural sense of atmosphere, an acoustic of involving proportions. Interestingly, and no doubt due to miking techniques, the clarinet sounded anything but pinpoint, while the piano reproduced with the appropriate image size, nicely balanced with the clarinet. In a very French way, the piano was a touch laid-back in the soundstage, less prominent than might be the case on another recording. The spotlight was always on the clarinet, accentuated slightly by the MC1201s in their way, yet the tonality and the elegiac, rhapsodic music has to be heard this way to be appreciated.

The Poulenc clarinet sonata is a real treat; I love it. It's adventurous, stunningly "intellectual," yet as light on its feet as Pan. The MC1201s dug it all out and delivered it whole, and it sounded very full. Don't play the next track, Romance for clarinet and piano, unless you're ready for some serious action from your spouse or S/O. The piano's lower registers typified the Big Macs' output: no overhang in the highs at all, a clean and detailed midrange tilting toward the lush side, and a definitely big, lush bottom end with heavy-hitting grunt, power, and sweep.

Not ready to let this disc go, I enjoyed the effusive last movement of the Poulenc sonata, Allegro con fuoco, in which clarinetist Florent H;aeau and pianist Patrick Zygmanowski sound like young artistic stallions, doing a zesty, wonderful job with the music. I could feel the enthusiasm, the timing, the pleasure in the notes. Bravo. Once again, I'd rediscovered the very purpose of the High End. Get this disc.

To round things out, I then turned to the innovative, floppy-limbed Moby and Play (V2 63881-27049-2). I'm indebted to reader Dan Turner (danturner@computron.net), who wrote to explain that the sound I'd picked up in the background of several tracks on this great recording was that of a film projector, "the sort we used to watch in biology class in middle and high school that would melt the film if it got stuck." I remember, Dan, all too well. I recall filmstrips on hygiene, and how to "duck and cover"! (New digital format! Everyone under the desks!)

The bottom end on track 4 of Play, "Why Does My Heart Feel So Bad," was, according to my notes, "big, powerful, and vast enough to sate all but the most jaded and demanding listeners." The sheer quality and power of the track's deep, abusive bass was massively impressive, as was track 12's kick-drum sound. In absolute terms, it sounded to me as if the MC1201s delivered ultra-power and grip on the bottom, but not as deeply or as cleanly as the Linn Klimax manages, if the Scots amp is a bit smaller in scale. It's just that everything was so BIG on the Macs, even and especially the bass. The deepest stygian depths were perhaps a slight bit masked by all the exciting stuff going on just above and up into the midrange.

Throughout Play, I heard that luscious, billowy midrange, that huge signature soundstage, "over, under, around, and through!" The JMlab Utopias seemed to disappear, the recorded soundstage taking over the acoustics of our listening area with no apparent effort whatsoever, particularly via the Linn CD12/Mark Levinson Reference 2 combo with all Cardas cables. That, as George Cardas would drawl, was special.

That film-projector sound at the beginning of Moby's "The Sky is Broken" sets the stage, functioning for me almost as an emotional dither that was very effective and evocative. Lots of detail through the big Macs, especially in the upper midrange. Moby's on top of the microphone—you can hear him almost swallow the thing! I sensed him in a very physical way wriggling around behind the microphone, which he "plays" in the same way he does other instruments.

Anyway, digging Moby deep, I picked up on the sweet, dreamy, somewhat plump lower midrange that, while not the last word in resolution, was enjoyable and entertainingly BIG. (What a surprise.) The midrange was cushy too, with high frequencies fully in attendance, the lower treble popping out at me as usual from the overall rather laid-back presentation.

Darling, give me my pipe, my slippers, and a beautiful woman...and you can have my pipe and slippers!—William Powell as Nick Charles in Song of the Thin Man

The McIntosh MC1201s are hugely powerful amplifiers whose true outer limits I never reached. The JMlab Utopias are so efficient that if I played them any louder than I did, I'd have blown my ears out. The Macs were like big, burbling V8s. You can mosey a 427 'Vette around at 5mph to leer at the babes, but a simple stab at the Loud pedal will launch you immediately into HyperSpace, leaving your hairpiece fluttering in the breeze. Or cruisin' on a $60k "hawg" (hardly) from California Choppers and "blatting" the proles with a run up the revs. Ah, life is good.

The MC1201 is not voluptuous like the MC2000, la dolce vita of tube amps. Nope, these monsters are for guys who'd rather get switched than have anything other than McIntosh. Like my pal Dan Billet. If you're a successful McIntosh kinda guy, you like a somewhat forward sound in the highs, and you absolutely love big blue meters...what's stoppin' you? If you're some kinda Liberal Democrat New Yawkah like yrs trly and you're spoiled rotten more often than not, well, you might pick a few nits—mostly in that little tipped-up region in the lower midrange that makes the MC1201 sound rather more "hi-fi" than I prefer on some absolute scale of perfection. And the MC1201 is perhaps not the last word in ultimate resolution.

But, as Kal Rubinson said some time ago regarding another component, that's my problem. It might not be yours.

Description: Solid-state monoblock power amplifier with output load impedance terminals for 8, 4, and 2 ohms. Output power: 1200W into 8, 4, or 2 ohms (30.8dBW, 27.8dBW, 24.8dBW, respectively), minimum sinewave continuous average power output rated 20Hz-20kHz. Output RMS voltage: 98V across 8 ohms, 69.3V across 4 ohms, 49V across 2 ohms. THD: 0.005% maximum from 250mW to rated power output. Intermodulation distortion: SMPTE 0.005% maximum if instantaneous peak power output does not exceed twice the output power rating. Dynamic headroom: 2.1dB. Frequency responses: 20Hz-20kHz, +0/-0.25dB; 10Hz-100kHz, +0/-3.0dB. Input sensitivity: 2.45V unbalanced, 4.9V balanced. Signal/noise ratio: 93dB, A-weighted, unbalanced (120dB below rated output), 97dB balanced (124dB below rated output). Damping factor: 8 ohm output, !w100. Input impedance: 10k ohms. Power Guard: <2% THD with 14dB overdrive. Power requirements: 120V, 50/60Hz, 15A UL/CSA.
Dimensions: 17.75" (460mm) W by 11" (280mm) H by 19.625" (500mm) D. Weight: 147 lbs.
Serial numbers of units reviewed: SL1002/1003.
Price: $7500 each. Approximate number of dealers: 300.
Manufacturer: McIntosh Laboratory Inc., 2 Chambers Street, Binghamton, NY 13903. Tel: (607) 723-3515. Fax: (607) 723-1917. Web: http://www.mcintoshlabs.com/.

Analog source: Forsell Air Force One turntable, van den Hul Grasshopper Gold cartridge.
Digital source: Linn CD12, dCS 972 and Purcell D/D converters, Elgar Plus D/A processor.
Preamplifiers: Balanced Audio Technology VK-50SE, Mark Levinson No.32 Reference, Conrad-Johnson 16LS.
Power amplifiers: Krell FPB 350MC and Linn Klimax Solo 500 monoblocks, Forsell Statement.
Loudspeakers: JMlab Utopia.
Cables: Digital: XLO The Limited, RCA and AES/EBU. Interconnects: Cardas Golden Reference, TARA The One, Synergistic Research Designer's Reference Discrete and Active Shielding. Speaker: Cardas Golden Cross, TARA The One, XLO The Limited, Synergistic Research Designer's Reference, Linn K400. AC: PS Audio Lab Cable, Synergistic Designer's Reference Master Couplers Squared, Coincident CST.
Accessories: ASC Studio Traps, Argent RoomLenses, API Ultra Enhancers, PS Audio P300 Power Plant with Multiwave upgrade, Signal Guard platforms, Black Diamond Racing shelves and cones, DH Labs cones, Bright Star Air Mass and Big Rock combo, PolyCrystal amp stand, equipment racks, cones, and cable towers.—Jonathan Scull

My usual practice is to subject amplifiers to a one-hour preconditioning period at 1/3 power. In the case of the humongous McIntosh MC1201, that meant 400W into 8 ohms from its 8 ohm output transformer tap. (One-third power is chosen because this maximally thermally stresses an amplifier with a class-B output stage.) To my surprise, the MC1201 shut down after 40 minutes or so, its heatsinks too hot to touch. This happened again during the testing. Each time, the MC1201 could be reset once it had cooled down, but this suggests that the amplifier is not recommended for continuous operation at very high output levels. (The Grateful Dead were supposed to have used powerful McIntosh amplifiers for their sophisticated and high-quality "wall of sound" PA system in the 1970s.)

The MC1201 was noninverting from both its single-ended and balanced inputs (the XLR for the latter is wired with pin 2 "hot"), while its input impedance at 1kHz was a low 8.6k ohms unbalanced, 17k ohms balanced. The voltage gain into 8 ohms varied as expected, according to which output transformer tap and input were used. The single-ended figures were 32.1dB, 28.1dB, and 25.9dB into 8, 4, and 2 ohms, respectively. The balanced figures were all 6dB lower, which will be on the low side for some preamplifiers.

The output impedance also varied according to the output tap used, and proved difficult to accurately assess due to the output voltage's tendency to drift a bit in the unloaded condition. But as best I could tell, the midband impedance was 0.28 ohm, 0.2 ohm, and 0.175 ohm from the 8, 4, and 2 ohm outputs, respectively, rising a little at 20kHz. This is pretty good for an amplifier using an output transformer. As a result, the modification of the MC1201's response due to interaction with the manner in which the partnering loudspeaker's impedance varies with frequency will be quite small. This can be seen in fig.1, which shows the MC1201's frequency response assessed from the 4 ohm tap. As expected, the variation with our simulated loudspeaker load was less from the 2 ohm tap, greater (±0.25dB) from the 8 ohm tap (neither shown).

Fig.1 McIntosh MC1201, 4 ohm tap, frequency response at (from top to bottom at 2kHz): 2.83V into dummy loudspeaker load, 1W into 8 ohms, 2W into 4 ohms, and 4W into 2 ohms (0.5dB/vertical div.).

Even though it uses an output transformer, the McIntosh's reproduction of a small-signal 1kHz squarewave (fig.2) was perfect, with no leading-edge ringing and a negligible downward slope to the waveform tops and bottoms. The 10kHz waveform (fig.3) was also superb, with just a slight increase in the leading-edge risetime associated with the ultrasonic rolloff seen in fig.1.

Fig.2 McIntosh MC1201, small-signal 1kHz squarewave into 8 ohms.

Fig.3 McIntosh MC1201, small-signal 10kHz squarewave into 8 ohms.

In general, the MC1201's THD level was very low, provided the output transformer tap was approximately matched to the load. But as can be seen from fig.4, when the load is significantly below the tap rating, there is an increase in distortion, particularly at high frequencies (though to what is still a low level).

Fig.4 McIntosh MC1201, 8 ohm tap, THD+noise (%) vs frequency at (from top to bottom at 4kHz): 2.83V into simulated loudspeaker load, 4W into 2 ohms, 2W into 4 ohms, and 1W into 8 ohms.

Fig.5 McIntosh MC1201, 8 ohm tap, 1kHz waveform at 455W into 8 ohms (top), distortion and noise waveform with fundamental notched out (bottom, not to scale).

Fig.6 McIntosh MC1201, 8 ohm tap, spectrum of 50Hz sinewave, DC-1kHz, at 805W into 8 ohms (linear frequency scale).

Fig.7 McIntosh MC1201, 8 ohm tap, HF intermodulation spectrum, DC-24kHz, 19+20kHz at 805W into 4 ohms (linear frequency scale).

Fig.8 McIntosh MC1201, 8 ohm tap, distortion (%) vs continuous output power into (from bottom to top at 10W): 8 ohms, 4 ohms, and 2 ohms.

Fig.9 McIntosh MC1201, 4 ohm tap, distortion (%) vs continuous output power into (from bottom to top at 10W): 8 ohms, 4 ohms, and 2 ohms.

Fig.10 McIntosh MC1201, 2 ohm tap, distortion (%) vs continuous output power into (from bottom to top at 10W): 8 ohms, 4 ohms, and 2 ohms.

From the 8 ohm tap, for example, more than 1500W are available into 8 ohms, with well over 2kW delivered into 4 ohms at the usual 1% THD clipping point. But "only" 700W can be delivered into 2 ohms from this tap. The power level indicated on the giant meter, by the way, was correct when the output tap matched the load.

I couldn't perform my usual pulse testing with the MC1201; its fully differential output is incompatible with the single-ended Miller Amplifier Profiler. However, given the humongous gobs of low-distortion power it can deliver, McIntosh's MC1201 should be capable of driving all real-world loudspeakers to very high levels with music program (rather than continuous tones) without breaking a sweat.—John Atkinson

Editor: The following bullets are comments on the technical section of the review, starting at the beginning of the "Measurements" section.

• The output stage is listed as class-B. It is actually a class-A/B output stage.

• A comment about the 40-minute operation at 1/3 power: This is done to keep the top cover of the amplifier from exceeding 65 degrees C, which is a requirement for CE certification. The unit is designed using parts that are safely operated at 80 degrees C and higher. Allowing the unit to shut down at 65 degrees C is extending the life of the product. The only music material that is really available today that is compressed enough to represent 1/3 power would perhaps be an FM radio station (if you could imagine listening to 400W continuous). It is reported that the amplifier needed to be reset when this occurred—the reset is automatic. Once the amplifier overheats, it mutes the input; after it cools down, it then unmutes automatically. There is no reset required by the user.

• The comment about the Grateful Dead using McIntosh amps: These amps were the MC2300s, which were forced-air-cooled. Physically they were the same size as the MC1201, but with a total output of only 600W.

• In reference to figs.8, 9, and 10: I would like to question the consistency in the 2 ohm load measurements in these graphs—especially fig.10, where the impedance is matched to the 2 ohm tap. Without knowing the exact test conditions or type of load that was used, in my experience in measuring the 2 ohm tap, the connection of the load can be extremely critical—especially in its mechanical integrity. I have seen this type of irregularity on the bench here when the connection is lacking in mechanical integrity. Each of the graphs seemed to show a consistent distortion response, except for the 2 ohm, which would lead me to believe that there is something not consistent with the 2 ohm test setup.

Here at the factory, each amplifier tap is checked, loaded with its respective impedance on the production line, and has to pass at 0.005% THD—as did the amplifier that was reviewed. This test is done from 20Hz to 20kHz at 1200W and at 12W.—Charlie Randall, McIntosh Laboratory