MAC Autoformers?

Someone is selling a MAC MA6500 Integrated claiming its superiority over the Ma6600 due to the fact that "it does not have the degrading autoformer design found in the MA6600". That is the first time I've heard a claim that the autoformer was a hindrance to better performance; I thought quite the opposite. What do you MAC Maves think?
For us non Mac enthusiasts the autoformer has always been proof positive that Mac had no idea how to design a transistor amp, perhaps they are coming to their senses at last.
I'm not even sure what the autoformer does. It seems like an effort to provide the same level of power no matter what the impedance load of the speaker is - which in theory sounds like a good thing. But I don't understand much of this. I did not know there was controversy regarding autoformers - so I wait to be enlightened in the issue here.
I agree with Stan. I just wrote this a few minutes ago:
Mac's autoformers kills the amps transparency characteristics.
Also some used to refer to them as having poor transient response(the autoformer). That was a big edge companies like Accuphase had over Mac transistor amps years back,plus other companies now.
I'm not nearly as knowledgable as our "in-house" expert, Aball, on all things McIntosh, but I do know that my MC7200 does not have the autoformers and it is one very nice sounding amp, probably one of the best McIntosh built for the money. As usual, opinions will vary...
I am not a Mc fan, nor am I a proponent of auto-formers such as speltz's, but I wouldn't be so quick to shun them or their use by Mc. Transformers are a mature technology that modern audio has only begun to tap (pun intended), ie- amorphous (metallic glass) cores are seldom used. One reason comes to mind, transistors typically don't have the same transfer characteristics between P and N types (PNP/NPN) and transformers allow use of one type for push pull operation. For me the "whole" is far more important than the parts.
go with a model with autoformers.
The MC7200 is one of the finest amps ever made by McIntosh BECAUSE it does not have autoformers (another being the MC122 - no meters though, 80w).
You have to admit this is confusing. Now it seems that Mac uses the autoformers in the "higher end" units. Why would the do that if it hurt performance? I can't imagine they don't have technical competence and the autoformer is some kind of bandaid for inferior SS design chops. Aball, where are you?
I would guess that that a Mac with autoformer will sound good => better => best depending on the speaker load. A very demanding speaker load, the autoformer will be of a benefit, therefore, in theory, better sounding. A speaker with a very benign load will sound better when used with a non-autoformer amplifier due to the simpler topology. Or, you can listen to both amplifiers and pick the one that sounds the best to your ears, but that makes for a very poor forum discussion.
If it gives such great benefit why don't other companies use them? It is quite true that transformers are a mature technology so if they gave an improvement in this area it should have been seized on by many of the "cost no object" amplifier designers. Krell , for example, will drive very low impedance loads at least as well as the Mac without transformers. The question here is whether their prime purpose is to improve the sound or protect the amplifier. Since the transformer is the prime weakness of tube designs it is hard to see how it will help SS ones.
I think that the McIntosh autoformer is utilized for a number of reasons. I have had a few amps with and a few without. The ones with sound better than those without, IMO. The cost, weight and size of the autoformer is probably the main reason McIntosh doesn't use them in certain amps. I have found that the non-autoformer amps lose detail and that "tube warmth" and seem to have a brighter less musical presentation, again IMO. The question as to why other manufactures don't use autoformers is probably due to them not wanting to add the circuitry to the output stage. But keep in mind that McIntosh designs their amps knowing they will use it and design with it always in the grand scheme. The non- Autoformer amps have a totally different topography it is not like they just add it to some and not others. I am quite sure that McIntosh realizes that the autoformer causes a level of diminished performance by it's employment. But I think in the overall scheme of things McIntosh builds their products with a few goals: Sound Quality, Product reliability, protection of circuitry and speakers. Maybe they are willing to sacrafice some sound performance to acheive a "built like a tank" amplifier that will provide years of reliable service, and let me add here, that this is my theory not fact. I have bought as mentioned many McIntosh amps and preamps. The one constant in all of these is they always work and they always sell quick and hold the majority of my investment.
McIntosh is not for everyone, but then neither is Chevrolet, Levis, or asparagus. Pubul57, my advice is buy the Mc amp with autoformers. You will receive maximum McIntosh performance and maximum resell when you move on.
If you want the best amp ever made, then spend the rest of your life reading the opinions of audio enthusiasts, myself included, among those found in many many forums. But in the end make your decision must based on 2 things 1)what you hear and 2)what you can afford at the time. This is all of course my OPINION only and I could debate this for weeks on end with those who disagree. But this is what I feel and you must adhere to the 2 decision makers listed above. As a final note, in my years of buying audio equipment and reading forums I can think of no other brand that receives more bashing than McIntosh. I have dealer that bashes Mcintosh all the time but in his secret room it is all McIntosh, go figure. However, I see them holding the some of the best resale values. Do what makes you happiest and enjoy your music the most that you can.
I am pretty sure that MAC had or has a patent on the autoformer. It is expensive to manuf. I have had both.
I would not refrain from a MAC purchase because it did
or did not have them. They do put them in their more expensive equipment. The autoformer does keep that sweet MAC sound with all loads. MAC's without autoformers do not have problems with loads either.

I would not call them degrading.....I saw the ad the poster
was referring is an ad. I would not give the same opinion. I have sold a few amps that were more powerful to the ear and went back to MAC.
Oh Boy! This is an old argument, and when it pops up, you invariably hear someone say that Autoformers add distortion, decrease detail etc. It is all nonsense. The proof is in the sound, and the amps with Autoformers sound fuller and more effortless and authoritative (to me) than those without. Bottom line, the "Mac Sound" is best expressed in the amps with Autoformers, and it's a great sound, so if you are going to get a Mac amp, I would say get one with Autoformers.
Different circuit designs accommodate different components. To say any amp is good or bad based on the fact that it has either transformer or direct coupled outputs without listening is just a foolish generalization.
I have used many Mac amps over the years (since 1978) except for the latest models, whose prices are truly hideous! My conjecture is the same as ONTJESR, the 7200 was/is the best amp they've made, and with no autoformers.. In my experience, all the autofromer models had a "flabby, not tight" bass. The 7200's bass is deep and tight. I always thought what most of you express, if they're so great, why don't other manufacturers use them? Mac claims it lets them match the loads to any speaker impedance. I own the 7200, and have yet to hear the un-tube-like sound some of you claim to hear. This is their best amp I've heard! THEO says it about right!
The reason I though the autoformer was a good thing is that my speaker manufacturer (Merlin)suggested that if I want to add an SS am (I own two tube amps that I switch around)to consider the MacIntosh with the autoformers, which is interesting in light of some of what has been said here in that they have a very easy load and very smooth impedance curve, where the autoformer would seem to be less needed. Well I think I'm going to decide based ergonomics and not worry too much about the AF/non-AF issue. Any opinions on differences in sound quality, or other considerations between the 6300, 6500, and 6600. Power is not an issue, my speakers run perfectly fine on 50 watts or more.
I think the 6300 is a sleeper......It does use THERMAL TRAK
which keeps it running cool all does not have
BASS/TREBLE controls but the pre-amp section is great.

It uses LED's instead of bulbs.......I thought the 6500
was quote unquote "louder" but the 6300 sounded better to me.

I like balanced inputs my self which the 6300 has.
With MAC people do not talk enough how important your source (cd player, dvd player, server etc.) is relative to your sound. Do not get me wrong, I know it is on all equipment, but you can REALLY hear the differences
on MAC stuff. Only as good as what you plug into it.

All three are good pieces of equipment. Never understood why the 6600 has such a bad rap.
That is funny about the guy who always bashes Mcintosh and has it himself. I know someone similar. According to my friend, McIntosh cannot do anything right except in his own listening room. Go figure.
Hi all, After reading this discussion I just thought I'd mention that I've noticed on the used market McIntosh amps that have autoformers seem to go for more money than the ones without. I've seen some Mac amps from the 70's go for more money that ones with out autoformer that were made in the 80's and 90's. Also I have a Mac MC2105 and I think it sounds much better than the Adcom or the Belles amps that I had prior to it. And go figure, the Mac is close to 40 years old and still works like a charm.

My System:

McIntosh MC2105 Amp
McIntosh C504 Preamp
Sansui TU666 Tuner
California Audio Labs Alfa DAC
California Audio Labs Delta Transport
Micro Seiki DDX 1000 Turntable w/ Sumiko Premier MMT tonearm/Linn Asak MC cart.
Musical Fidelity X-LPS phono preamplifier
Vandersteen 2CE Speakers
Loving my MA 6600 with the AF's. My understanding autoformers give you full power at any impedance. That's a bad thing...I don't think so. And after some many decades I think MAC could employ there use without degradation. That other makers don't use them, cost and the thinking it is not necessary for their designs. But McIntosh has always tended to go the extra mile, and have the philosophy of "bonus built" components.

As for some of the differences in their integrated amp line up. Along with the very musical presentation some nice features, such as electronic tone controls and level matching. Secondary output to drive another amp. Led lighting among others makes for a very nice package in the MA 6600.
Had the 2105 and the 7270,havent heard Mac amps without them so cant compare.I can say both came close to Ayre,CJ,Counterpoint and a couple others.This would be with Merlins,YMMV,cheers,Bob
McIntosh is simply making some different design decisions in using autoformers. Comparing an autoformer amp to a Krell, for example, one notices a distinct difference in how they're rated. The Krell tries, and usually succeeds, in having the ability to output a consistent maximum voltage level regardless of the impedance of the load. Because the voltage limit is fixed the maximum output current varies. So the Krell puts out X volts into 8/4/2/1 ohms, and that might correspond to 300/600/1200/2400 watts, for example, depending on the load.

The autoformer amps have a different design goal, output a consistent maximum current regardless of the load's impedance, using the autoformer to "match" the load to the amp's output stage. So a McIntosh amp might be rated at 1200 watts into 8, 4, and 2 ohms.

Which is "better"? Well, that depends. Assuming your maximum listening levels cause a current draw well within the limits of the amplifiers, I can't believe there will be much of an audible difference in sound attributable to the autoformers. They don't add distortion, but they *can* affect the system's frequency response.

The autoformer adds some resistance in the output path, so the so-called damping factor, or the output impedance of the amplifier, is probably going to be a lot higher than a direct-coupled amp, like the Krell. It's all that wire in the autoformer; it adds resistance. How is this audible? It may not be, but if you have speakers that present a very low impedance load you could have a roll-off or dip at those frequencies where that happens, I suppose. Will the roll-off be audible? I don't know, but some speakers do present very low impedance at some frequencies (early Legacy Focus, Apogees, and Wilson Watts come to mind), so if you own one of those I'd stay away from autoformer amps, but that's not intended to be some deep pronouncement.

Autoformer designs allow a manufacturer to spend more on producing high current into higher impedance loads, so assuming there was some real relationship between cost and price (there really isn't for products like this) for X dollars you could get more watts into 8 ohms than with the non-autoformer design. Take a look at the MC1.2 for example. 1200 watts/ch into 8 ohms. What does Krell offer that puts out 1200 watts into 8 ohms, and how much does it cost? Of course, the MC1.2 will still put out 1200 watts into 4 ohms, while the Krell is putting out twice the watts into 4 ohms, but since the MC1.2 starts out so much higher in power, you don't really see the two design approaches differ until very low impedances, when even a low-end Krell amp is putting out over 2000 watts, assuming you have a 220v/30amp power line running to the silly thing.

So are autoformer amps better or worse than direct-coupled amps? For most speaker loads you'll never hear a difference, but I admit to strongly preferring the direct-coupled approach, assuming you can afford a good enough amp that it does indeed act like a good voltage source, like a Krell. I think a very low output impedance is indicative of a better design, but I wouldn't bet five cents on my ability to tell the difference in a double-blind test. It's just my opinion, but I'm the buyer so I get to have one that counts!
I don't own McIntosh, but for the last 10-15 years, their amplifiers have been excellent and increasingly desirable sonically. I am a SET tube amp listener, yet ironically I am most likely to become a McIntosh owner when I can find the money and space for a pair of MC1201 mono blocks or their MC1.2kw successors.

Philosophically, as someone who has built amps and as a listener, I am inclined toward direct coupled designs, but the proof is in the listening. Forget your topological biases and there will be no doubt that no existing direct coupled McIntosh solid state integrated amp equals the musicality, tone density and overall fidelity of the autoformer-based amplifiers above them in the line.

The 6300 and 6500 are certainly quite good for what they are, and well-made too. The autoformer 6600, 6900 and 7000 are as a group distinct step-ups in musical truth. The next step function boost in fidelity comes when the quad differential circuit is added to the mix, in the power amps from 402 and up. I'd love to see a 7000 add the quad-diff circuit.

Go have a listen and decide for yourself.

I noticed I made a grammatical error in my last post that could mislead people. Autoformers increase the output impedance of the amp relative to direct-coupled designs, which leads to a LOWER damping factor. My apologies for being such a lousy editor.
I wonder if you run a bunch of drivers , in series, which means higher impedance if the wattage stays constant... -with an auto former-

So let's say... Since I like to use DJ'ing as an excuse to buy audio gear for my home system.....(lived that lie since I was 17 in 1981) could I run several JBL Alinco magnet 18" subs in scoops in series and not continuously half the power as I run into higher impedance loads??? That to me is better than running low impedance loads and stressing the amps and generating tons of heat and a lower dampening factor.

I know there is no free lunch... but would I be better off running say... (8)18"
woofers (8 ohm each) in series parallel arrangement to give a 8 ohm load with a Mcintosh as opposed to running them in parallel for a 1 ohm load with a Krell?
Read what Mac's designer says. A push-pull amp has, by its nature a lower output impede in the bottom stage. The autoformer corrects this mixed-matched problem and matches the sometimes large fluctuations in total output impedance some the speaker always gets the same current no matter its impedance so it will not blow because of a demanding signal. It is BOTH a sonic and safety issue.
My 2 cents is after talking to Mctintosh Tech Teryy somebody in Knoxville TN, research,the verdict is that autoformer as opposed to direct is a different but very d=techniacal approach. Your own ear is the judge. Mu experience is with MC 2200 paired with Martin Logan motion 10 +sub. Results were very Impressive used 3 different venue's (rooms).

So my Net answer is I think due to dedication & quality, Mcintosh had a game winner.

 Very versatile  amp with rich smooth Mcintosh sound, attention to quality, is the defining difference but people forget how dedicated Frank WAS.
other companys don't have autoformers because mcintosh has a patent on it!
If you read Ken Kessler's book, there's significant disagreement about Autoformers between the various designers.  I think it might've had marginally better relevance in the very early days of Solid State.  Now there are even CAR stereo amps that can run .5 ohms all day at negligible distortion.  It has to be a cakewalk for well isolated AC.