I gather that output regulation relates to how closely a tube amplifier's voltage output will vary so that the amount of power (watts) presented to the speaker will correspond to the magnitude of the input signal, thus compensating for varying speaker impedances which change as a function of FR. In short, if impedance increases, voltage will also increase. This in turn will increase current. All of this is accomplished through NF.No, that's not right Bruce. Output regulation in this context refers to how little or how much the amplifier's output voltage will vary as a function of load impedance, for a given input signal. Period. The magazines define it based on the range of impedance variation of a particular simulated speaker load. The ARC specs define it based on a load variation from 8 ohms to infinity ohms (i.e., an open circuit). The tighter the regulation, meaning the smaller the +/- number, the LESS the voltage will increase as load impedance increases, and the LESS the voltage will decrease as load impedance decreases.
An ideal voltage paradigm amplifier will have a regulation of +/- 0.0000 db. Its output voltage will not change at all as load impedance varies. And, per Ohm's Law, for a given output voltage the amount of current drawn by the load will vary inversely with the impedance of the load. So since power is proportional to voltage x current, and equals voltage x current in the case of a purely resistive load, the power delivery of a voltage paradigm amplifier will NOT "correspond to the magnitude of the input signal."
And a voltage paradigm speaker is, by definition, one that is designed based on the expectation that it will be driven by an amplifier which behaves in that manner. Such as the small two-way I described in my previous post.
If a SS amp is asked to feed current into a high impedance segment of the speaker's FR spectrum, somehow the amp must increase its current output or else power (watts) will decrease.In that situation power WILL decrease, but if the speaker is (correctly) designed with the expectation that it will be used with a solid state amplifier, having negligibly small output impedance, the acoustical output of the speaker will nevertheless be correct. In other words, a voltage paradigm speaker whose impedance varies significantly as a function of frequency will require less power at frequencies for which its impedance is high than at frequencies for which its impedance is low, to produce a given amount of acoustical power.
If I am tracking so far, what I don't understand is how a so called zero NF amp (tube or SS) can properly respond to impedance values which change as a function of FR in order to maintain constant power through a speaker's FR spectrum.So at this point it should be clear that a voltage paradigm amp does NOT maintain constant power as load impedance varies. That is the behavior that a power paradigm amp, having relatively high output impedance and generally minimal or no feedback, will approximate to some (usually loose) degree.
As far as feedback is concerned, an amplifier whose output impedance is negligibly small in relation to the load impedance, at all frequencies, will behave as a close approximation of an ideal voltage source, maintaining an output voltage that does not vary significantly with load impedance (as long as it is operated within the limits of its voltage, current, power, and thermal capabilities). Given a low enough output impedance (as in the case of the Ayre amplifiers) it will do that to a close approximation regardless of how much feedback it does or does not use.
Two closing points:
1)Feedback, as it is usually applied in this context, does not cause output power to "correspond to the magnitude of the input signal." It causes output VOLTAGE to more closely correspond to the magnitude of the input signal (multiplied by some gain factor).
2)As Ralph has pointed out in the past, tonal balance problems result from using speakers with amplifiers that are not of the same paradigm.
Best,
-- Al