One more time: autoformers?

The Atma-Sphere amp I own will put out more power into higher impedances up to a certain point, which I believe is 32 ohms. After that point the power will drop. So you really need to know the impedance peaks of the speaker and where they occur as opposed to the nominal impedance.

Music Reference amps are designed for light loading. For example, the RM-10 I own will exhibit lower distortion and provide other benefits if you use the 4 ohm tap on an 8 ohm nominal speaker. The trade off is about 10 watts of power. I am not certain that this applies to all amplifier designs.

BTW - Some McIntosh solid state amps used autoformers and among the McIntosh crowd these amps are quite desirable.

Thanks again Clio. I recall reading somewhere that certain Atmasphere amps had a 32 ohm ceiling. I tried the 4 ohm tap. The music su*cks. Went back to the 8 ohm tap.

Btw, been using my sub-woofer a bit more aggressively than before, i.e., raised the gain a little and raised the cut-off frequency to about 80 Hz. Going by ear, I think the sound stage opened up quite a bit. I don't know why. Maybe my finished basement is a giant bass (or is it base? - LOL) trap.

I'm speaking from experience and don't really care about theory or numbers. My Atmasphere MA-1's were not doing a good job of controlling the lower frequencies of my Aerial 10t's. They sound flabby. With autoformers the bass dramatically thighten up and allowed for a more linear presentation without a loss of sound stage. I already owned the 10t's when I bought the Atmasphere amp and preamp so I had to do something to solve the mismatch. In my case it worked very well but I must add the cavet that I'm in the process of setting but my brand new Merlins which should be a much better match to the OTL's. Autoformers are only suitable for certain very specific situations. If all works well with the Merlin's my autoformers will be for sale as the 10t's are headed for the Man Cave and will be driven by a Bryston amp. No autoformers necessary.

Hi Drambuie. Thanks for your post. I'm waiting for ARC to come back to me with its thought about how well my ARC amp matches with my speakers. If ARC says all is well, I'll stand pat. But if not, I may be in the market for Zeros. If you decide to unload your Zeros, please send me a message and I'll give you a status update. I'm hoping to hear back from ARC very soon. If ARC thinks Zeros might improve my sitution, maybe we can help each other out. Thanks again.