Most of these posts are right on. Although I think the doubling up and halving down isn't exact with Autoformers due to coupling effects. Theoretically, yes, but in reality, no. Take a look at the Stereophile measurements of the MC501 and you'll see what I mean. For example, peak output power was 1000W with 4 Ohms taps driving a 2 Ohm load.
Incidentally, check out also how the 501 only has +-0.1dB modulation with the reactive loudspeaker load. The 8 Ohm tap has a damping factor of 100 and the -3dB is at a high 120kHz.
Undertow - I made a similar observation as you about damping factor. Some tube amps really have wonderful bass - perhaps not the most "potent" but very natural. John Atkinson and Roy Gregory also made this oberservation. Many forget that damping factor is related to both the frequencies of the musical signal and to frequency-dependant reactances. So an amp's ability to handle phase shifts is the real deciding factor for how well controlled the bass is or not. Besides, a driver is going to have its own mechanical and electrical impedances, especially a bass driver, so its own decay time will impose real limitations. From what I have seen, these limits basically render any DF above 50 a wash.
But we really knew all this already - particularly if you agree that global negative feedback is bad or that parallelling a bunch of BJTs (or even worse, MOSFETs) is not the best way of keeping a signal pure and unadulterated.
Arthur
Incidentally, check out also how the 501 only has +-0.1dB modulation with the reactive loudspeaker load. The 8 Ohm tap has a damping factor of 100 and the -3dB is at a high 120kHz.
Undertow - I made a similar observation as you about damping factor. Some tube amps really have wonderful bass - perhaps not the most "potent" but very natural. John Atkinson and Roy Gregory also made this oberservation. Many forget that damping factor is related to both the frequencies of the musical signal and to frequency-dependant reactances. So an amp's ability to handle phase shifts is the real deciding factor for how well controlled the bass is or not. Besides, a driver is going to have its own mechanical and electrical impedances, especially a bass driver, so its own decay time will impose real limitations. From what I have seen, these limits basically render any DF above 50 a wash.
But we really knew all this already - particularly if you agree that global negative feedback is bad or that parallelling a bunch of BJTs (or even worse, MOSFETs) is not the best way of keeping a signal pure and unadulterated.
Arthur