Hi Everyone,

I was just wondering what people's opinions were on the famous (or
infamous?) McIntosh autoformers, i.e., whether you think they are
useful, how they change the sound you hear, et cetera. I've heard some
people say they like the sound of the MC7200, for example, which is a
direct-coupled amp without autoformers.

I have a Mac 2300, Mac 2200 (both have autoformers), and a Mac 2002 (no
autoformers), but have not yet done side-by-side comparisons. It
probably would be most interesting (and fair) to compare the 2200 and
2002, since they have the same rated power, but differ mainly in the
presence/absence of autoformers (2200 has 'em, 2002 doesn't...cue
music..."Almond Joy's got nuts, Mounds don't!")


Thanks, and looking forward to your comments,

Adam


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Adam wrote:
Hi Everyone,

I was just wondering what people's opinions were on the famous (or
infamous?) McIntosh autoformers, i.e., whether you think they are
useful, how they change the sound you hear, et cetera. I've heard some
people say they like the sound of the MC7200, for example, which is a
direct-coupled amp without autoformers.

I have a Mac 2300, Mac 2200 (both have autoformers), and a Mac 2002 (no
autoformers), but have not yet done side-by-side comparisons. It
probably would be most interesting (and fair) to compare the 2200 and
2002, since they have the same rated power, but differ mainly in the
presence/absence of autoformers (2200 has 'em, 2002 doesn't...cue
music..."Almond Joy's got nuts, Mounds don't!")


Thanks, and looking forward to your comments,

Adam



The McIntosh output transformer design became famous in tube amplifiers.
For good reason too. They solve a number of difficult design problems
very nicely, and are relatively simple to manufacture to boot!

Briefly, they permit much wider bandwidth than the typical output
transformer, for any given tube, power and core material. The downside
of the McIntosh ouput transformer is that quite a bit of "extra" voltage
swing is typically required since the gain of the output stage is, iirc,
2 - as opposed to much higher gains in the typical plate loaded output
stage.

The McIntosh "Autoformers" were created at a time when transistors had
several "weaknesses" which included a lack of complementary high power
devices, and issues with breakdown voltages (although you can argue that
an autoformer might actually make that problem worse...). Also, McIntosh
wanted to capitalize on their reputation based on the tube type output
transformers and appeal to those who were already in their customer base.

Another aspect of this was that the autoformer got rid of the problem of
blocking DC with a large cap (typical of early transistor amps) by using
the Autoformer.

Since the autoformer changes the way that the devices "see" the load,
and also acts as something of a bandwidth limiter, there are some
advantages/disadvantages to be found there as well.

In my view, what you get in a typical *vintage* McIntosh amplifier is
more a function of the *rest of the circuit* than the output autoformer,
or before that, the bifilar wound unity gain output transformer... that
is the sound is dominated by McIntosh's particular circuit design and
component choices to a great deal. Said another way, take the
transformer/autoformer out and build a completely different circuit, it
will likely not sound particularly like a McIntosh.

No one else did that for a good reason.
McIntosh had patents on these designs.

_-_-bear


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