For the past few years, McIntosh Laboratory has been refreshing and expanding its product line at an unprecedented pace. The subject of this review, the MC1.25KW mono amplifier ($12,500 USD each), made its debut in late 2017, and I haven’t been able to take my eyes off it since. Imagine my elation when Mark Christensen, McIntosh’s marketing coordinator, offered to send me for review a pair of MC1.25KWs and their flagship preamplifier, the C1100 (review in the works). In discussions with Christensen, I learned that the MC1.25KW is both a replacement for and an evolution of McIntosh’s beloved MC1.2KW amplifier, and offers more dynamic headroom, upgraded parts and connection points, and refreshed industrial design and lighting.


As was the MC1.2KW in its day, the MC1.25KW is now McIntosh’s most powerful single-chassis monoblock. Measuring 17.75”W x 12.3”H x 22”D, this 158-pound behemoth can produce 1200W of continuous power into 2, 4, or 8 ohms, with bursts of peak power in excess of 2kW. Equally impressive, and perhaps even more important, the MC1.25KW has a specified total harmonic distortion of just 0.005% and a signal/noise ratio of 124dB (balanced operation). It should make about as much noise as a block of granite sitting on a velvet pillow.

McIntosh Laboratory

The visible differences between the MC1.2KW and MC1.25KW are many yet subtle. On the top panel, directly behind the glass faceplate, are two new glass-topped enclosures: the one on the left displays printed information for the autoformer, the one on the right information for the power transformer. Between these, the brand and model number are displayed on a circular glass plaque surrounded by a chunky aluminum rim. Toward the rear are two pairs of large aluminum heatsinks that run the full height of the amp and are cast to form the “Mc” monogram. The two sinks of each pair are capped and joined by a thick aluminum ventilation plate finished to match the trim ring and front grab handles.

The front of the MC1.25KW is largely unchanged from the MC1.2KW, with the exception of new LED lighting with improved distribution of light. The glass covering the 11” blue wattmeter remains 1/2” thick, but now, for greater precision, is UV-cured with high-resolution print instead of the silk-screening used on the MC1.2KW. On the faceplate are two knobs, each with three positions: the Meter knob, at left, can be set to Lights Off, Watts, or Hold, the last position telling the meter’s needle to remain at the maximum output; the Power knob, at right, can be set to Off, Remote, or On. Between these knobs are an illuminated McIntosh logo and the Power Guard and standby indicators, and outside the knobs are the faceplate’s aluminum endcaps and handles.

McIntosh Laboratory

Around back are three pairs of McIntosh’s new, patented, Solid Cinch speaker binding posts, and an IEC power receptacle whose new position (relative to the one on the MC1.2KW) makes it possible to use bigger power cords. All of these are vertically oriented. I’m no fan of vertical power inlets -- they’ll be torqued and strained by the weight of whatever power cord is used -- but my large Clarus Crimson cords had no trouble fitting, and the connection was solid. What I did like was that the MC1.25KW has both balanced and unbalanced inputs and outputs, making bi- or even triamping a snap. These ins and outs, at top center of the rear panel, can also be used to pass along input signals to a subwoofer or another system. Directly below them are 12V power-trigger ins and outs, an auto on/off sensor, and a balanced/unbalanced toggle. The case is made of stamped and polished stainless steel, and rests atop four damped feet of new design with attractively chamfered profiles.

The MC1.25KW, like the MC1.2KW, is Quad Balanced -- that is, its circuitry is fully balanced from input to output. Twin matched 600W amplification stages operate in push-pull, their outputs combined by an autoformer. The autoformer, designed to provide DC protection and to ideally match the amplifier output stages to a speaker load of 2, 4, or 8 ohms, works in harmony with McIntosh’s Quad Balanced architecture. This unique Quad Balanced design, I’m told, makes it possible for an amplifier to produce very high power output with very low levels of noise. While that sounds great in theory, I’ve always wondered how it works. I did a little research; here’s what I learned:

Quad Balancing sends the same signal down two identical amplifier signal paths in each channel of an amplifier. In the case of the MC1.25KW, the same monaural audio signal is fed to two 600W power modules, but one signal is inverted: its waveform rises where the original signal’s waveform falls, and vice versa. The two signals, inverted and noninverted, then enter the autoformer, whose dual coils are wound in opposite directions; as the inverted signal travels through the autoformer, it’s reinverted, restoring it to its original form -- and simultaneously, the noise produced by each amplification module is canceled out. The clean power from both modules are then combined to perfectly double the power output.

McIntosh Laboratory

McIntosh’s Quad Balanced architecture was used in the MC1.2KW. New in the MC1.25KW are upgraded circuit components, heavier-gauge internal copper wiring, an updated power transformer, new precision metal-film resistors, and new film capacitors. The MC1.25KW also has 50% more energy capacitance: a total of 162,000µF, or 450 joules. This not only helps provide more control over power-sopping low frequencies, it’s claimed to boost the MC1.25KW’s dynamic headroom by 0.2dB over the MC1.2KW, for a total of 2.2dB. McIntosh has also replaced the transistors used in the MC1.2KW with more advanced, higher-current output transistors selected for their ability to help “eliminate thermal equilibrium lag,” and which are directly connected to the newly designed heatsinks. These new transistors are ON Semiconductor’s ThermalTraks, which permit instantaneous monitoring of transistor temperature.

No McIntosh amp would be a McIntosh amp without a host of features designed to protect it and lengthen its working life, and the MC1.25KW gets the royal treatment, beginning with a new power-management system. This feature, which can be defeated by flipping a toggle switch on the rear panel, monitors the input signals and switches the amp into standby mode after having detected no signal for 30 minutes. In standby, the MC1.25KW draws just 0.5W. The MC1.25KW is also equipped with McIntosh’s time-proven Power Guard technology, which prevents it from being driven into clipping, and works with McIntosh’s Sentry Monitor thermal-protection circuitry, which protects the output stages from overheating.


Setting up 316 pounds’ worth of monoblocks is a labor of love, but thanks to the MC1.25KWs’ handy handles and thoughtful packaging, I could have done it unaided. Luckily, I had help, but nonetheless applied the KISS principle and placed these bruisers on a pair of butcher-block amp stands sitting on the floor.

McIntosh Laboratory

Once they were in place, hookup was a snap: I removed the interconnects that usually feed my reference Simaudio Moon Evolution W-7M monoblocks and plugged them into the MC1.25KWs. My Audio Research Reference 6 preamplifier, PS Audio DirectStream DAC, Torus AVR 20 power conditioner, and Paradigm Persona 7F speakers all remained in place, and all was connected with Kimber Kable balanced interconnects and speaker cables and Clarus Crimson power cords. Also on hand and awaiting review were McIntosh’s C1100 preamp and EMM Labs’ DV2 DAC.

Easy on the ears

Having recently reviewed Merrill Audio’s Element 118 monoblock amplifier ($36,000/pair), I expected to hear a tonal shift with the McIntosh MC1.25KWs, and I did. The Element 118 is an exceedingly neutral, transparent, and revealing amplifier; in many ways, it’s a reviewer’s dream amp. The McIntosh MC1.25KW’s sound was warmer, richer, smoother -- in short, not quite as tonally balanced. Nonetheless, I found the MC1.25KWs’ sound to be compellingly indulgent overall. But in stark contrast with the Element 118 -- an amplifier whose sound I find to be uncolored until I push it very hard -- it was clear that McIntosh has engineered the MC1.25KW to sound better than the MC1.2KW, yet maintain a degree or two of McIntosh’s traditional house sound.

Katie Melua’s voice in the title track of her Call Off the Search (16-bit/44.1kHz FLAC, Dramatico) sounded surprisingly similar to what I’d heard through the Element 118s and my reference Simaudio W-7Ms: clean, detailed, and articulate, with a level of realism that would be welcome from any amp. Nuances, however, such as the decays of producer Mike Batt’s piano notes and the thrums of Melua’s guitar strings, were more difficult to hear than I’m used to with my W-7Ms, and were entirely absent in comparison to what the Element 118s lay bare. It was as if everything above about 5000Hz had been rolled off by 1-2dB. On the other hand, I loved the weight and depth of Tim Harries’s bass guitar, and Melua’s dynamic vocal inflections were on a par with both other pairs of amps -- and a noticeable improvement over what I remember hearing from the MC1.2KWs.

McIntosh Laboratory

Listening to “Man in the Long Black Coat,” from Bob Dylan’s Oh Mercy (24/88.2 FLAC, Columbia), I quite enjoyed watching the thin black needles of the Macs’ meters bounce around to the expertly reproduced plucks of Dylan’s acoustic guitar. As I raised the volume, I was amused to see those once-lively needles suddenly peg at the -40dB mark, when Tony Hall’s deep and resolute bass enters. The control over each note exhibited by the MC1.25KWs was as resolute as it was ground-shaking, and despite the sound levels approaching the upper limits at which I normally listen, I got the distinct impression that these amps had only begun to approach the output level at which they like to operate. So I drove them harder, pushing the needles up to 120W and beyond. I soon realized what these big Macs are all about: unrelenting power.

Only one other amplifier I’ve reviewed has ever instilled in me the confidence that the MC1.25KWs did, and that was Simaudio’s Moon Evolution 888 monoblock, at nearly five times the price. The 888s were not only the most powerful, but also the quietest amps I’d ever reviewed. In the opening seconds of “Man in the Long Black Coat,” in which only one instrument plays against an ink-black background, I again “heard” a noise floor so low it was almost inaudible. In fact, the MC1.25KW’s specified signal/noise ratio of 124dB is 4dB quieter than the monster Moon’s. Realizing that the MC1.25KWs seemed to sound better the harder I pushed them, I played “Born Slippy,” from Underworld’s live album Everything, Everything (16/44.1 FLAC, JBO), and was taken back a decade, to when I saw this band perform in Toronto. I adjusted the volume to a level commensurate with what I remember hearing at that concert, and reveled in the sound of applause in the background against Karl Hyde’s voice and the rhythmic, punchy beat of the drums. As soon as I heard the repetitive synth notes that define this song, which originally appeared on the soundtrack of Trainspotting (1996), I couldn’t help but close my eyes and reminisce in an inner fog of nostalgia. Still a hint reserved in their reproduction of upper-frequency nuances and spatial cues, the MC1.25KWs were the antithesis of slow or laid-back with “Born Slippy,” “Cowgirl,” and “King of Snake.” Bass notes absolutely thumped. As I moved on to other electronic tracks -- e.g., “Serendipity,” from Armin van Buuren’s A State of Trance (16/44.1 FLAC, Armada) -- I appreciated the absence of the glare and varnish I hear with more uncompromisingly revealing amplifiers such as the Merrill Element 118s and, to some extent, even my Simaudio W-7Ms.

McIntosh Laboratory

When I switched gears and listened to an SACD rip of “So Far Away,” from Dire Straits’ Brothers in Arms (24/88.2 FLAC, Vertigo), the rich, fulsome sound of the MC1.25KWs was again fully displayed. In the opening seconds, the cymbal taps in the left of the soundstage were well delineated, with fast transient control. Omar Hakim’s thwacks of the drum skins were fast and dynamic, with just a hint of decay, and his kick drum was convincingly punchy and impactful. As Mark Knopfler chimed in on electric guitar, nothing seemed to be missing, and the aural image of each instrument was depicted on a deep, wide soundstage, just as it should be. The tambourine taps at right center weren’t quite as present as I’m used to hearing, but still had a subtle shimmer, and were defined well enough that I could hear individual zills.

As that track ended and “Money for Nothing” began, I again succumbed to the urge to pump up the volume. As the Macs’ needles bounced around well past the 120W mark and items on nearby walls rattled, I couldn’t help grinning. The volume was as high as I dared push my Paradigm Persona 7F speakers, and the sound simply grew in volume, scale, and intensity -- there was no compression of soundstage or diminution of three-dimensionality or inviting tonality, nothing sounded shrill or varnished, the amps’ control of bass notes didn’t diminish, and there was no lack of depth or impact to that grin-provoking bass. As the sound filled my room, everything was just . . . louder. When I’ve occasionally pushed my speakers this hard with the Simaudio W-7Ms I’ve heard much the same quality of sound, but with a hint of glare that inevitably prompts me to soon ramp the volume back down. And when I pushed the Merrill Element 118s this hard, their sound became bright, quickly leading to listening fatigue.

The fact that the MC1.25KWs sounded a bit more relaxed at lower volumes is assuredly the reason they were able to play so loud while remaining inviting. Typically, when someone tells me a product sounds “relaxed,” I assume they mean that it sounds dull or boring. That wasn’t the case with the MC1.25KWs. Proportionate to its lack of micro-level detail, there was greater image focus, specificity, and body. Music, regardless of genre, was presented with ease and a silk-smooth refinement, yet this amp’s pace, rhythm, and timing were spot on.

McIntosh Laboratory

And I was beguiled by the MC1.25KW’s reproduction of bass. At low volumes, there was a sense of weight, kick drums were punchy, and notes were articulated, transparent, and tonally accurate enough that I could easily discern the differences among electric, synth, and double basses. I don’t hear this level of resolution from my reference monoblocks, because at lower levels there simply isn’t enough bass volume for me to do so. At moderate volume levels, the weight, punch, and dynamic drive of the MC1.25KW grew in scale and articulation, and this control and body is maintained even at outlandish listening levels, much as I heard from Simaudio’s Moon Evolution 888. Male and female voices were consistently vivid and intricately communicated, which goes a long way toward implying that the requisite level of detail is there, even though it isn’t. I suspect that, without a more resolving pair of amplifiers sitting right next to the MC1.25KWs for instant comparison, some listeners might not notice that anything at all is missing.

Summing up

McIntosh Laboratory’s MC1.25KW monoblock amplifier sounds absolutely beautiful. It could communicate just a bit more top-end inner detail, but its lush, sophisticated sound is also part of its allure. Physically, the MC1.25KW represents one heck of a value for $25,000/pair. It is expertly engineered, skillfully assembled, full of top-quality parts, and made of some of the best materials available. If you believe that an amp is an amp and that all amps sound the same, compare the MC1.25KW directly with whatever other monoblocks you deem, well, comparable. I guarantee your paradigm will be shattered. Enthusiastically recommended!

. . . Aron Garrecht

Associated Equipment

  • Speakers -- Paradigm Persona 7F
  • Subwoofers -- JL Audio Fathom f112 (2)
  • Amplifiers -- Merrill Audio Element 118 monoblocks, Parasound Halo A 51 (five-channel), Simaudio Moon Evolution W-7M monoblocks
  • Preamplifiers -- Anthem AVM 60, Audio Research Reference 6
  • Digital-to-analog converters -- EMM Labs DV2, PS Audio DirectStream, Simaudio Moon Evolution 780D
  • Sources -- Oppo Digital BDP-103 universal BD player; Intel NUC computer running Windows 10, Roon
  • Interconnects -- Analysis Plus (USB), Clarus Crimson (S/PDIF), Kimber Kable Select KS-1116 (balanced)
  • Speaker cables -- Kimber Kable KS-6063
  • Power cords -- Clarus Crimson
  • Power conditioner -- Torus AVR 20

McIntosh Laboratory MC1.25KW Mono Amplifiers
Price: $12,500 USD each.
Warranty: Three years parts and labor.

McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, NY 13903
Phone: (607) 723-1545
Fax: (607) 724-0549