McIntosh and Autoformers. . .?

You are right Zaikes. With speakers above 8 ohms there is a lesser need to consider the AT. I am not sure just where the crossover point of diminishing returns lies but I would probably pick 10-12 ohms. So even with an 8 ohm speaker I personally think the benefit of an AT could be considerable.

Even though McIntosh claims 35db feedback in their amplifier the fact is that, with a relatively low impedance speaker such as the Magnepan, the driver circuits will be working harder, pushing themselves closer to their limits so to speak, as well as the output transistors. Feedback aids this process. With the larger operating envelop and higher output stage currents we get negative attributes such as higher transient modulation distortion and, for lack of a better term, some amplifier signature.

With the AT in the McIntosh, I would not think the driver and output circuits will not be operating as widely in their envelop. Less driver swing, less output stage current, thus less dynamic distortion and less of a "signature". Keep in mind that some of these distortions are hard to characterize and I am not an expert. The propeller head on Audio Asylum may be good site for further discussion.

I see that Paul Speltz has posted on this thread. I highly recommend his advice on amplifier/speaker compatibility as he not only markets the "Zero" AT but also has much experience in their application. There is a couple reviews of the "Zero" in press; one on the "TNT" audio site and one in the January edition of AudioXpress magazine. I think its January, could be off a month though.

Following Zaikes question, I'm using an Atma-Sphere MA1 MkII.2 with Kharma Ceramique 1.0 speakers. These speakers are nominally rated at 8 ohms, not sure what the impedance curve looks like though. The amps seem to drive the speakers well, but I'm wondering if an autoformer might significantly improve the sound? Ralph Karsten suggested it might or might not depending on the shape of the impedance curve. Does anyone have any experience with this combo or sage advice? Thanks!

Germanbox, your speakers and amp combo would appear to fall smack in the middle of the grey area with regards to sonic improvement with the addition of an auto-transformer. My experience was with the MA-1 Mk II, not II.2. Yet I would speculate that the benefits with the AT on my Maggie 3.6s would be the same whether the MA-1 version was the II or II.2.

My friend, you have an outstanding system to say the least. You deserve the best that it can offer, whether this means adding the AT or doing nothing. So, for the comparatively small price of Paul Speltz's "Zero" transformers, my recommendation is to contact him and work out an audition arrangement. Or, you can opt for Ralph's more expensive (buy probably no better) "Music Z" auto-transformer. Fit, form and function is basically the same. Then you can provide us with a follow-up report and further shrink that grey area where the AT works well.

I like the autoformer. I've owned some nice Krell and Levinson, but after listening to the Mac I hear a slight ocillation in those, mostly on strings and voices. I never noticed it before and it is slight. I think it is due to the AF, as it presents a steady load to the output stage. With a direct coupled amp, as the impedance of you speaker changes with frequency responce, and music is all over the place, the output stage will dish out more or less current so it's flucuating alot. Certainly the Krells and Lev's are up to it but it's still flucuating, and they may have their strengths too. Take all the advice you can get, but make sure you "buy" what sounds good to you or else you are a loser.

Nealhood, very good advice... thank you. Hopefully, Paul will allow me to audition it and I definitely will report back should I be able to arrange this.

How important is it to use good cable from amp to autoformer? I've pushed the finances almost as far as I can (wife has that serious look on her face if even a small box is delivered to the house) and the thought of matching speaker cable quality for the short run to the autoformer is giving me the shakes.