To cut to the chase here, I think that what is contributing to the disagreements in the recent posts is that the protagonists are focusing on two different things. Unsound is focusing, I believe, on the how the MAXIMUM power ratings of the McIntosh and Wolcott amplifiers vary as a function of load impedance. Ralph is focusing, I believe, on how the power outputs of those amplifiers will vary as a function of load impedance when those amplifiers are operated WITHIN their maximum limits.
If those amplifiers are operated within the limits of their output voltage, output current, output power, and thermal capabilities, their high damping factors (made possible by the use of feedback) will cause them to behave as if they have the very low output impedances which by definition characterize a voltage source. Especially in the case of the Wolcott (damping factor >500), and to a lesser but still reasonably close approximation in the case of the MC's (MC30 damping factor 12; recent version MC75 damping factor 18; recent version MC275 damping factor 22).
Provided that the amp is operated within its limits, a damping factor of 22 will cause the 4 ohm tap of the MC275 to behave as if its output impedance is 4/22 = 0.18 ohms. To a close approximation that is negligible in comparison with most speaker impedances, which will therefore result in essentially negligible variation of output voltage as a function of load impedance. Which in turn will result in output power increasing in proportion to decreasing load impedance. Provided, again, that the amp is operated within its limits.
The fact that the amplifier's MAXIMUM rated power does not increase substantially (or at all) into decreasing load impedances, as would be the case for a solid state amp (up to a point), is unrelated to that but I believe underlies the disconnects in the discussion.
Regards,
-- Al
