Anything as " fast" as SPECTRAL gear?

02-18-15: Csontos
Al, as you and Ralph are obviously the two most technically knowledgeable, I think it most appropriate for the two of you to also define/describe amplifier 'speed' from a subjective/sonic perspective.

From a subjective perspective, I think of "fast" as referring to the ability to reproduce musical transients in a "clean" and accurate manner, as opposed to a "sloppy" and inaccurate manner. As ZD said on 2-9-15, "you need to listen to how the system is reproducing the attack, resonance and decay of whatever instruments are on the recording."

I would emphasize, though, that speed from a subjective standpoint and speed as characterized by risetime, bandwidth, and slew rate are two different things, which do not have a necessary or direct relation. It seems entirely conceivable to me that an amp having a 100 kHz bandwidth could be subjectively "faster" than one having a 1 mHz bandwidth.

Although in many cases there may be an indirect relation between faster bandwidth/risetime/slew rate and subjective speed. For example, use of a given amount of feedback in a really high speed circuit may not result in as much Transient Intermodulation Distortion compared to its use in a slower circuit (as Ralph, Psag, and I alluded to earlier). Less TIM distortion meaning more accurate reproduction of musical transients, by definition.

BTW, re "the two most technically knowledgeable," let's not overlook Bombaywalla, who is certainly no slouch when it comes to EE technical matters, and perhaps some of the others who have responded as well.

Best regards,
-- Al

Thank you Al. I thought there is always going to be a direct causal effect of actual amp speed and subjective/sonic speed. That's very interesting. I understand the obvious descriptors of a really good amp but there's another effect/indicator of subjective speed which is observable. It may be that I have a too limited perspective on what transient performance is. The things I'm referring to are effects of ambiance being injected where you can hear it's instantaneous up front presence less subtly than the engineer may have intended probably expecting it not to be noticeable, and maybe with a sparkling almost grainy effect. As if you can hear that sound being constructed. Also for example a string being stretched or when they are sliding up or down the neck of the instrument, or soft consonants like the word 'you' for example where after the initial attack the remainder of the tone is so consistently immediate as to convey the same sense of speed as the transient. Or the precisely contained decay of a kick drum where you can hear reverberations clearly/sharply. Or even a trombone doing it's thing with a sense of strength and immediacy that denotes speed. I have a pair of Meridian 105s that are uncanny in their ability to convey this sense of speed. I also have a pair of the famed LOW TIM LSR&D Superamp monos designed by the late Dr. Marshall Leach of Georgia Tech. Although they both display equally competent transient performance, the Meridians have that sense of immediacy that raises them a notch above. I also have a GAS500 that has this sense of immediacy but not quite as fast in transient performance.

If the relationship between technical parameters and subjective perception is indirect or vague, then how does someone set out to design a 'subjectively fast' amp? Is it just a crap shoot? Technically, what descriptors must an amp possess in order to facilitate subjective speed? Isn't this the goal?

I do recognize those here with knowledge and pay attention to their conversations. But it's you and Ralph who seem to stand out among the others for me.

BTW, re "the two most technically knowledgeable," let's not overlook Bombaywalla, who is certainly no slouch when it comes to EE technical matters, and perhaps some of the others who have responded as well.

thank you, Almarg, for the acknowledgement. :-)

If things are going well you will not hear 'speed' in an amplifier. If you do seem to recognize such based simply on highs and transient response, IMO/IME that is likely due to a coloration and not anything else (and often caused by trace amounts of higher ordered harmonic distortion).

Real speed is evident if the soundstage is deep and wide but not unnaturally so (this is because with speed comes correct phase response); the amp will be relaxed at high frequencies but obviously able to play them with a black background. I hesitate to say any more as so many other factors are involved/so many variables can exist...

To me, "Speed" seems more of a real issue with various transducers than with amplifiers.