I've read that low-impedance loudspeakers (typically defined as those with a nominal impedance of 4-ohms or less) are not well served by amplifiers that have output transformers. The reasons that have been given include:
1. Poor current transfer due to the transformers (low-impedance speakers draw more current) and
2. Poor damping factor due to the high output impedance of the transformers relative to the low loudspeaker impedance
Despite these issues, my dealer says that my McIntosh amplifier (mine uses the McIntosh "autoformer" output transformer) will sound spectacular with my Thiel 4-ohm loudspeakers. I haven't been able to test this claim yet (my MC352 is in the shop getting shipping damage repaired).
So my question is: All other things being equal (yeah - I know they never are, but this is a thought experiment!), will an amplifier without audio output transformers perform better with low impedance speakers than one with audio output transformers? If there are, in fact, real world issues that negate all or part of the above theories, please enlighten me.
Of course, once my amplifier comes back from the shop, I'll listen for myself. If the sound isn't satisfactory, my "plan B" is to buy an (output transformerless) integrated amplifier. Also, if anyone has personal experience with low-impedance speakers and McIntosh autoformer amps, I'd LOVE to hear of your experiences. Thanks! Boomzilla