Seems to me that there's a fair amount of mis-information being batted around, here. The use of autoformers on the output end of an amp is used to ensure that there is the best transfer of power from the amp to the speakers when the speaker load is attached to the most appropriate tap for that speaker's impedance curve.
This is the same electronic principle as found in matching a Moving Coil cart via a Step Up transformer into a phono preamp, and is the basis for any matching of 2 devices where low level signals need to passed with minimum loss of energy.
If you compare the output specs into 2,4, or 8 ohms for the solid state Mac amps that do and do not have output autoformers, you'll see that the specs for the ones with autoformers will quote the same power output at all impedances. The amps without autoformers will show rising power output power as the impedance goes down. The thing here is that the non-autoformer will tend to get hotter driving lower impedance loads since there is a larger impedance mismatch. Think of that heat as power that didn't get to your speakers from that mismatch.
BTW, Mac amps are not _normally_ driven into clipping due to the Power Guard circuit, which limits output drive as maximum power is approached. You can stil abuse the amp if you really want to but I can tell you from direct experience that this feature has saved many a set of speakers in professional situations - not to mention drunken college parties.
Cheers,
David
This is the same electronic principle as found in matching a Moving Coil cart via a Step Up transformer into a phono preamp, and is the basis for any matching of 2 devices where low level signals need to passed with minimum loss of energy.
If you compare the output specs into 2,4, or 8 ohms for the solid state Mac amps that do and do not have output autoformers, you'll see that the specs for the ones with autoformers will quote the same power output at all impedances. The amps without autoformers will show rising power output power as the impedance goes down. The thing here is that the non-autoformer will tend to get hotter driving lower impedance loads since there is a larger impedance mismatch. Think of that heat as power that didn't get to your speakers from that mismatch.
BTW, Mac amps are not _normally_ driven into clipping due to the Power Guard circuit, which limits output drive as maximum power is approached. You can stil abuse the amp if you really want to but I can tell you from direct experience that this feature has saved many a set of speakers in professional situations - not to mention drunken college parties.
Cheers,
David