Describe ube sound vs solid state

Look deeper, or at least to the first Wolcott link showing specs that I provided on 04-03-15:
http://www.wolcottaudio.com/WA_Pres_specs.htm

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

^^ Exactly. Thanks Al.

Al, thank you for clearing that up.
I will say that there I still have some misgivings about power rating and the ability to adapt to lower impedances of the above mentioned tube amps, as the sensitivity varies in a constant ratio to the impedance of typical loudspeakers.
To put in this context (using Al's reference to MAXIMUM power output), the more robust of the amps under discussion (and perhaps of all tube amps?); the somewhat unique Wolcott's standard 8 Ohm power rating of 180 Watts when outputting into a 2 Ohm load would be the equivalent of a 60 Watts standard 8 Ohm power rating of a high quality solid state power amp.

Hi Unsound,

Yes, it's true that some robustly designed solid state amps rated at 60 watts into 8 ohms will be able to supply 240 watts into 2 ohms, while the Wolcott's 180 watt rating into 8 ohms increases only slightly into 2 ohms, to that 240 watt value.

As I said earlier, though, as long as the amps are operated within their maximum capabilities, those maximum ratings will not be relevant to how their output power varies as a function of load impedance. What that variation will depend on is their effective output impedance ("effective" referring to the fact that feedback is taken into account), which btw equals speaker impedance divided by the amplifier's damping factor. If that output impedance is negligibly small in relation to speaker impedance, corresponding to a high damping factor, there will be essentially no variation of output power as load impedance varies, within the limits of the amp's maximum voltage, current, power, and thermal capabilities.

The extremely high damping factor of the Wolcott puts it firmly in solid state territory in that respect. And the highish damping factors of the MC's (relative to most tube amps) will have a similar effect, although to a somewhat looser approximation.

In saying all of this, btw, I'm ignoring the fact that the max power ratings of different amplifiers may not be precisely comparable, as a result of having been measured based on different standards, with different pre-conditioning warmups, different distortion levels, etc. But those are separate issues, not specifically related to tube vs. solid state.

Best regards,
-- Al