McIntosh Integrated Amplifiers

Autoformers vs. No Autoformers

What are the differences between the two types of McIntosh integrateds?

I'm not really familiar with autoformers or the advantage of them other than handling large Ohm swings? Is that correct?

Thanks very much. Someone please enlighten me because I really want a McIntosh amp and if I buy one without autoformers is it a true "McIntosh"?
A timely question, as another current thread, on Mac reliability (6500), seems to have turned into a comparison of the 6500 vs. 6900, and non-autoformers versus autoformers. What other Mc's don't have autoformers, other than some of the integrateds?
Really, to give you a good idea about this, one would need to know what speakers you would drive with the Mac Integrated, to discuss any advantage of the Autoformer output, in coupling with your speaker connection.
Of course a Mac without autoformers is a true "Mac"! My MC7200 amp doesn't have them, and I personally wouldn't have one with them, having owned several Mac amps with them. The autoformers allow the amp to put out the same rated power into ALL speaker loads. Without them, my amp has a rated power of 200 wpc into 8 ohms/300 wpc into 4 ohms. This is only my personal opinion, but if autoformers were so great, why do you not see them in other high-end manufacturer's products? Don't get me wrong, I have owned and loved Mac gear since 1978, I just hate autoformers.

Currently I have a Krell 400xi driving a pair of Proac Response 1sc's.

I have heard Mac's without autoformers and they do sound great and have lots of power. I'm just curious about the differences in the two designs.

Sid42, why do you hate autoformers?

Thanks for the reply's.
There are a couple of different threads on the whole question of autoformers vs. direct-coupled approach for Mac power amplifiers - most of the arguements are very much parallel to such other unsolveable audio debates, especially the transformer vs. transformerless one.

But a couple of points specifically about McIntosh . . . the main thing is, the autoformer and autoformerless amps aren't two totally different design approaches, in fact within a given generation, the rest of the circuit design is virtually identical.

Virtually all solid-state amplifiers exhibit a point where, as the load impedance goes down, distortion starts rising fairly quickly - this is due mainly to intrinsic semiconductor physics. An amplifier designer can make some choices that affect at what impedance this starts to happen, but as with everything else in life . . . there are tradeoffs. An autoformer can be used to alter this curve as well, and it seems that McIntosh usually prefers the set of tradeoffs associated with the autoformer over some other choices they could make in their output stages.

The MC7200 and its ancestor, the MC2002, are the oddballs in the Mac amplifier line, in that they are higher-end amps that don't use autoformers. My guess is that these amps were engineered at a time where many in the market felt that an amplifier should have a very high advertised "damping factor", and McIntosh couldn't deliver a high number with their current autoformer technology - so direct-coupled amps were developed to satisfy this. However, McIntosh has revised some of their feedback techniques with the autoformer amps, and their recent (autoformer) amps have damping-factor specifications similar to direct-coupled amps like the MC7200, so they probably feel that a high-end direct-coupled amplifier is no longer a necessary part of their line.
Yes, a few good threads exist on this subject. On the question "why doesn't everyone use them?" As I recall, they are expensive to produce and McIntosh already has a production facility for these. Tooling up a factory for these would be an expensive proposition. Secondly they add a lot of weight and also cost - things that don't bother audiophiles - but for the larger market not where manufacturers want to go.

I've always wondered if autotransformers have any effect on the output waveform. Certainly a McIntosh with autotransformers has a unique sound smooth yet still able to produce detail without raising the hair on the back of your neck.

I haven't listened to the 7000 integrated but I could tell a noticeable difference between the integrateds and separates with the separates sounding much better IMO.
To answer your question, Worldwide, as to why I'm not fond of autoformers, all the amps I've had with them have had rather flabby bass. Kirkus is right, other than the autoformers, there isn't a difference in the amps design. The autoformerless units do have a high damping factor, compared to ones with them. There are also other amps in the lineup without them, being the MC7106 and 7108, which are multi-channel amps. If Mac dropped the autoformers, since they are costly to build, as was noted, and increase the weight tremendously, maybe more folks could afford them. Some of the prices on their newest models are hideous! But hey, Mac is still a great product, and the final choice is your ears. Happy listening!
Worldwide, Do your best to try and listen to both types. Most likely you will prefer one over the other. The speaker of choice could also affect your decision. I prefer the AF types.

Even if the poll said 90% preferred AFs, you might be in the other 10%.
I own a MC-126 which doesn't have autoformers. I find it a little more forward and quicker than my 7270, but I prefer the warmer sound of my 7270 with my current setup.