McIntosh Laboratory MC462 power amplifier Page 2

Sticking with my arsenal of past R2D4 picks, and because I knew it would make me smile, I put on Count Basie & His Atomic Band doing "Roll 'Em Pete," from the killer collection Complete Live at the Crescendo 1958 (5 CDs, Phono 870245). Joe Williams nails it to the boards: "Well, you're so beautiful, but you've got to die someday. / All I want's a little loving, just before you pass away." Now that was something to die for—I had to laugh with pleasure. Via the MC462, Basie's piano was charging hard and taking no prisoners. The saxes and brass had such wallop I felt I was being spanked—in a good way.

I needed to hear the MC462 with genuine three-way speakers, preferably a pair difficult to drive. Audio Classics Ltd. was kind enough to loan me a new pair of Bowers & Wilkins' floorstanding 702 S2s, reviewed in May 2018 by Kalman Rubinson. In his sidebar accompanying Kal's review of the 702 S2s, JA measured an easygoing sensitivity of 90.2dB for the B&Ws. However, though this model's nominal impedance is specified as 8 ohms, JA found that it dipped down to 3 ohms in the bass, and concluded: "I think [the 702 S2] should be used with amplifiers that are comfortable with 4 ohm loads."

Got one right here. I hooked up the 702 S2s to the MC462's 4 ohm speaker taps and listened, knowing I was getting the same 450Wpc of power no matter which taps I used. And thanks to a heads-up from John Swenson's review in January 2019, I had on hand the perfect music—the Grateful Dead's Pacific Northwest '73–'74: Believe It If You Need It (3 CDs, R2 572292). These live recordings are from the period of the Dead's tours famous for the Wall of Sound, the massive PA system they briefly toured with in the 1970s. The Wall was powered by 48 McIntosh C2300 stereo amplifiers—a direct ancestor of the MC462—and put out a tidy 28,800W!

The thing to listen for is Phil Lesh's hot-rodded Alembic bass guitar, dropping what he called his "bass bombs." The Harbeth 30.2's specified low-end limit is a relatively modest 50Hz, whereas the B&W 702 S2's is a claimed 28Hz. With the MC462 firmly in the saddle, the B&Ws rode along with the Dead through the monstrous "Truckin'/Jam/Not Fade Away" sequence from the Portland Memorial Coliseum in May 1974. Though not summoning the 32'-high bass soundwave that John Swenson states the Wall of Sound could create, the McIntosh-B&W combo still let me feel the foundation of Lesh's bass, and produced a strong visceral sense of the thundering barn-burning the Grateful Dead were capable of 45 years ago.

Now that I'd fished a bit in pools downstream from the McIntosh MC462, what about casting a line upstream? My McIntosh C2300 preamplifier uses 12AX7A tubes in its line-level and phono stages. Was it perhaps time to branch out in my choice of preamplification? I swapped in J E Sugden's solid-state Masterclass LA-4 line preamplifier, reviewed in the April 2019 issue by Jim Austin and then sent on to me by John Atkinson. The LA-4 is a compact, streamlined, nothing-but-the-facts preamp. As of this writing, I have yet to read what Jim and John think of it, but I don't expect their takes to be less than positive.

With the Sugden LA-4 in the chain, I dipped into one of the great complete cycles of Beethoven's piano sonatas, recorded for Telarc by John O'Conor in 1987. I listened to Sonata 21, "Waldstein" (CD, Telarc CD-80160), O'Conor playing a fine Hamburg Steinway. Everything was right about the sound—no sense whatsoever of any strain, and an extremely even sense of timbral distribution throughout the audioband. The CD booklet states that the monitor speakers used for this recording were B&W 801Fs. For additional corroboration, I walked downstairs to the living room and played a bit of the "Waldstein" on my 1936 Steinway Model M. Yup—that's what a piano sounds like.


I'm a newbie when it comes to streaming, but I'm glad I waited—I'm really digging what I'm hearing from Qobuz's new US service. Streaming at hi-rez from my Mac laptop (McIntosh Laboratory licensed the use of the name "Macintosh" to Apple years ago) through my Bricasti M1 DAC, I browsed a new cycle of Sibelius's seven symphonies, recorded over several years by Paavo Järvi and the Orchestra of Paris (24-bit/96kHz FLAC, RCA/Sony SYNX 19075924512). The Sugden-McIntosh-B&W combo tore the roof off, with fantastic energy propelling the end of Symphony 3. Sibelius also loves him some pizzicato—and the plucked strings in the second movement were woody and delicate.

But while I enjoyed the performances, I wasn't wild about the overall sound of these recordings. When the strings played hard, things started sounding a bit hashy and brittle. Was it the recording or the gear? Like many people, I own more than one Sibelius cycle—all I had to do was pull them out and compare. Switching to the cycle with Lorin Maazel leading the Vienna Philharmonic, from the early 1960s (3 CDs, London 430 778), I got a fast answer. The gear was correctly revealing the truth about the recordings. The Maazel cycle has a far richer, less strident sound, and that's what I heard. For good measure, I put on the same movement of Symphony 3 from the cycle recorded by Leif Segerstam and the Helsinki Philharmonic Orchestra, from the early 2000s (4 CDs, Ondine ODE 1075-2Q). Here were warm, strong, yet varied sonics, in comparison to the other two, and my pick in this three-way Sibelius faceoff.

It was time for bringing it all back home, as the Poet said. After many more moments musicaux like those described, I restored my system to what it had been before, the only new element being the McIntosh MC462. To eliminate guesswork I used my personal North Star, a recording of my own compositions for chamber ensembles and string orchestra, which I conducted—Tight Lines (LP/CD, Stereophile STPH022-1/2). The MC462 became a literal studio reference, a conduit: I stood there again before the musicians as they made music out of dots on pages.


. . . and it comes out here
I count 81 amplifier models issued by McIntosh Laboratory through 2003. I'm told the count is now well over 100—a company with that kind of history now competes mainly against itself. McIntosh fans have their favorites from the company's various design eras. As listeners, we also have our individual likes and dislikes—some rational, some not so much.

My own No.1 priority in the reproduction of music is the living, breathing re-creation of the harmonic series. That is the "nature" in music, the vibration of the spheres. You'll want to be thoughtful in choosing what to pair the MC462 with, upstream and down—this amp interrogates whatever it comes in contact with with such authority that it could veer to the analytical side of the sonic spectrum. With a simpatico system the McIntosh MC462 will bring the breath of life to your music.

The McIntosh MC462 Quad Balanced power amplifier sits today on the bottom shelf of my rack like a stocky Buddha, calmly radiating energy as the forest creatures—eg, the red squirrels that winter inside the walls of our old Victorian—gather 'round, smile, and nod their heads. One thing they all agree on is the price—$9000 is more than fair for the excellence delivered, given the inflationary forces wafting through the High End. The senses of ease and literally quiet power created by the MC462 are palpable and most welcome. A first-round vote pick for induction in Class A of the next edition of our "Recommended Components." Highly recommended—insisted on, even.

McIntosh Laboratory, Inc.
2 Chambers Street
Binghamton, NY 13903
(607) 723-3512

Bogolu Haranath's picture

JA1 said it all ..... "It is an extraordinarily well engineered, exceptionally powerful amplifier" :-) ........

Ortofan's picture

... why do we need recordings with a resolution of any greater than about 18.5 bits?

Also, if the moral is to match the MC462's nominal output to the lowest impedance magnitude of the loudspeaker used, then which tap - 4 ohm or 2 ohm - is the better choice for a speaker that has a minimum impedance of 3 ohms, such as the B&W model used by the reviewer?
Depending upon which amplifier output tap is selected, there seems to be a trade-off between maximum power output and lowest distortion.

georgehifi's picture

Yet why review such an amp with these speakers that are easy loads, even a NAD3020 could drive them? Surely those that intend to buy this 50kg back breaker of an amp, are going to go for more substantial speaker than these?
This amp should have been reviewed with Wilson Alexia or similar to see if it perceived persona is more than just skin deep, and not a show pony.

Cheers George

PaulRS's picture

Correct me if I'm wrong, but a single-winding autoformer that McIntosh uses will not block DC. Only a transformer, such as used on most tube amplifiers will do that.

SNI's picture

@Paul IRS
You are right about that.
An autotransformer does not provide electrical isolation, as it is a single winding transformer.
Primary and secondare are connected both electrically and magnetically.
Double winding transformers are only connected magnetically.
Hence the DC isolation.
Anyways a two winding transformer is not very good at blocking DC, as the core can be saturated, and then build up heat.
Thus the primary task of a transformer is either step-up or step down or isolation, not a highpass filter
Generally the autotransformer is a step up or step down device only.
Historically the autotransformer came into HIFI because of lack of power. The Atotransformer coupled as a step-up transformer could increase the voltage swing on the secondary side. At that time most speakers were relatively high impedance, thus a higher spl was possible.
In modern times high voltage swings are no problem, as transistors have develloped, so no one uses transformers anylonger besides MacIntosh.
For what ever reason they still do, I don´t know.
No transformer is a linear component, they are pretty heavily inductive,
so using a transformer in the output, will introduce distortion of the signal.
Of course this can be reduced with NFB, but basically it is a workarround of a problem, that isn´t really there.

Alan Tomlinson's picture

"No transformer is a linear component, they are pretty heavily inductive,
so using a transformer in the output, will introduce distortion of the signal."

Well said. That said, there are a variety of distortion forms out there, and some of them are euphonic. No less an engineer than Rupert Neve has been using transformers in his recording consoles for a long time, and it's not because he didn't receive the memo about transformer-related distortion. In short, McIntosh probably has a fundamental sonic reason for favouring autoformers.


Alan Tomlinson

SNI's picture

@Alan Tomlinson
You might be right, that specific persons regard the distortion introduced by transformers as euphonic, and thus musical in some sense.
This point of view is not shared by everyone though.
I.e. if you look at very high end microphones like DPA (used for measurements by Stereophile, amongst many), Neuman, Shoeps etc. do have TL versions of their top performers. (TL = Transformer Less)
The TL versions are recommended over the transformercoupled ones, but the transformercoupled can be neccesary in studios with long and mixed cable runs.
In smaller set-ups with few mikes, the TL is recommended for its cleaner sound and better transparancy.
I´ve heard the difference, and there is no doubt, that the TL is the better choice in the purist cases.

But the choice of microphones and the choice of a lot of other recording gear, can be seen as a part of the musical expression.
An A/B stereo recording of Nirvana ore something, would probably not work in real life.
But IMO this kind of deliberate colouration should be held inside the recording studios. I don´t think it is wise to introduce stuff like that in the reproduction chain, as well as I cannot imagine that doing so will go well most of the time.
Good and sensible engineering with as few idiosyncratic elements as possible, will be best for the long haul I think.
Not that listening should be left out of devellopmentlabs, indeed not.
But the chances for good sound are present, but not in anyway garantied by good measurement results. On the other hand, I´ve not yet experienced good sound from equipment with bad measurements.
I don´t like distortion, no matter how euphonic it might be. It´s always there, and will be recognised as distortion eventually.

Best regards


jmsent's picture

No, an autoformer can't completely block dc. But when you consider the dc resistance of the autoformer winding, where the input tap is connected to the output transistors, and the other end of the winding is ground, you're probably looking at something on the order of a fraction of an Ohm. So, it's pretty likely that a dc fault condition would let very little voltage through to the speaker and pretty quickly blow an internal fuse in the amplifier. I believe that later Mac amps also have considerable additional fail safe circuitry in them that would disconnect the speakers in the event of any dc offset condition.

Bogolu Haranath's picture

There is information about transformer and auto(trans)former in Wikipedia :-) ..........

SpeakerScott's picture

The autoformer will present a very low impedance to DC. The older autoformers on McIntosh amplifiers are approximately .5H winding inductance (more on that in a bit) and less than .2 ohms DC resistance. If the amplifier sticks to one rail the autoformer will cause the primary mains fuse to blow protecting the speakers. It is an elegant solution to DC protection.

The inductance limits the autoformer from becoming a substantial part of the load for audio frequencies. As long as the high pass filtering for the amp is at a high enough frequency.

The autoformers themselves are incredibly linear, even the ones I've tested from McIntosh amplifiers from the mid 70's and earlier will pass a full power signal at less than .05% THD.

SNI's picture

200 mOhms is actually a lot in that part of an amp.

Best Regards


SpeakerScott's picture

Not really...that's still a damping factor of 40 for an 8 ohm speaker which is more than enough to minimize frequency response variation and not impact time domain performance in an audible significant way.

SNI's picture

I don´t agree.

jmsent's picture not just a function of the DCR of the autoformer. There's the feedback loop which effectively lowers the output impedance to very low values. JA has measured this in the review. The effective output impedance is on the order of .09 -.13 ohms at the 8 ohm tap...certainly more than adequate. I realize you don't like the amp, and I'm not here to defend it as I think it's overkill for a home audio system. But there's no disputing that it measures quite well in most respects. Your philosphical objections to autoformers not withstanding, what are your issues with it?

SNI's picture

My issues with autoformers is that you get high output impedance.
0,09 Ohms makes a DF @ 89, and that is not very much for a solid state amp.
So the McIntosh has the disadvantage of a low dampingfactor and on top of that it stil has a global feedback loop.
When using global feedback, you should at least have a higher DF than even non feedback amplifiers can achieve.
You can se it clearly on its power delivery.
There is not very much distortion, but power decreases rappidly with load.
That means when you call upon its power into a real speaker load, it will not stay linear at all levels.
Thus the non linearities will be amplitude related, and will not show on a THD measurement.
I really don´t like the idea of "hiding" an amps misbehavior behind a transformer, no matter what type it might be.

jimtavegia's picture

If you think of 6db per bit for dynamic range, one would think that 96db would be enough. Now I doubt there are many 16 bit chips made any more and 24 bit chips are so advanced and of such high quality and can playback more formats.

What I want is more samples per second and find that at 96khz there is just a much more smoother sound, more accurate to me and that is what I want to hear. I know mathematically that 192khz is better resolution, but my nearly 72 year old ears have a hard time hearing the improvement, but I'm sure it is there, probably. There is no mistake to me that 2496 is a great format for hearing what there is recorded in PCM. In my home studio I record everything at 2496 and some material at 24192.

DSD is even better, but now that is pretty much limited to downloads as no one I know is making affordable SACD players anymore. I wish they were. This Mac amp will handle anything you pass through it and, as the review showed, reveals flaws in poorly recorded material.

Bogolu Haranath's picture

Denon makes DCD-1600NE, which can play CD and SACD ........ MSRP $1,199 :-) ..........

jimtavegia's picture

I did not know that Denon had one. I was sorry to see Oppo go.


Ortofan's picture

... more likely to be found in the video department.
A few DVD/Blu-ray disc players have SA-CD compatibility and a set of RCA audio output jacks.
The $330 Yamaha BD-S681 is one such unit.

Dtb1180's picture

Did you compare this amplifier directly to your tubed McIntosh? Also have you heard the lower powered models that are not quad balanced and do they sound similar? I have owned tubed (MC275 mark 6) and solid state (MC252 I think) and they have a similar house sound. What do you think?

Dr. M.'s picture

Greetings, Thanks for your focused questions.I still own my wonderful MC275; of course with ability to swap tubes comparisons will change.My review comments do refer to prior extended listening to the MC275. Please see my question to Charlie Randall in the attached interview now posted, about the "McIntosh Sound." Some people hit on Mac for this- I view it as a strength.

No, haven't spent recent in-house time with prior solid-state McIntosh amps- only under show and shop conditions. Enjoy the long and winding Mac road! - Best, Sasha M.

Anwar's picture

Hi Sasha, you tested the MC462 with Harbeth M30.2. I have the MC452 and recently acquired M30.2. Which speaker taps you use and prefer for M30.2? Thanks.

JGlacken's picture

Hi Sasha,
I see we have the same dac. Have you tried the Dac direct to the 462 and if so is it compatible?
I am thinking of buying a 462, but want to check this out first.


granosalis's picture

I have Tannoy Canterbury GR with Nominal impedance 8 Ohms and Minimum Impedance 5 Ohms. Which output Autoformer tap should I use?

direstraitsfan98's picture

Hello, Mr. Matson, I finally made the plunge to purchase this amplifier based on your excellent and well written review of this product. Much appreciated, I look forward to seeing more McIntosh products looked at in the future. I would like to suggest Stereophile takes a look at the C2700 tube preamplifier, and the C53 or C70 solid state preamplifiers. Thanks for your consideration.

Cacophonix1961's picture

I would very much like to see a review of the most affordable McIntosh Integrated. Seeing reviews of kit that I cannot afford depresses me! Could you? Please.