Anything as " fast" as SPECTRAL gear?

02-19-15: Csontos
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?

Thanks for the nice words in your post, Peter. I'm not sure how to answer your question, though. Consistent with Ralph's comment, there are simply too many variables that can be expected to be involved to be able to formulate a meaningful general purpose answer. It stands to reason that wide bandwidth and fast risetime and slew rate will tend to be helpful, but only indirectly if at all once they get above a certain point (for example, the 200 kHz bandwidth figure I cited earlier, corresponding to 10x the nominal upper limit of audibility).

As with most sonic characteristics of audio components, I would expect accurate reproduction of those sonic attributes which contribute to a realistic perception of "speed" to be more than anything else a function of the knowledge, experience, and thoroughness of the particular designer, and of his or her priorities in addressing the innumerable tradeoffs that enter into any design.

Best regards,
-- Al

I am absolutely amazed to find this out Al. So it's more or less a matter of alchemy? Like an unguarded secret by someone successful in coming up with the right recipe but in the end not being able to put their finger on just what makes or breaks the design. So a great mind with knowledge and experience still must exercise some trial and error in designing a circuit. Like art. I've heard it said you're not an artist til someone else says you are. I think there's some merit in that saying.

Its not alchemy, but a designer does have to know what he is doing and it is the mark of a good engineer to know what is 'negligible' and what is not.

Beyond the alchemy part of your post, it is pretty much correct. Even a talented engineer will fall well short of possibility if he or she does not remain a student of the practice (or 'art'), especially that of the specific product and its goals. There is always something new to learn- I find that engineering/technical types that make the assumption that we know everything there is to know about audio are the same ones that have terrible stereos.

You have to have an open mind and in particular, be open to the fact that you don't know everything!!

I get that Ralph. But even the alchemists were careful not to make the same mistake after an explosion. I don't know why I thought it was basically cut and dried. I don't have two amps that sound the same, even among identical examples. I guess I just think it should be entirely straight forward as to how to achieve a pre-conceived sonic result. I thought the differences are borne entirely of preference and not ability. IOW, lots of designers need conceptual adjustment. I suppose it's yes and no/know.

^^ that has been my experience. The ear/brain system is the final arbiter and not enough is known about how we perceive sound to be able to go off of bench specs (which rarely have anything to do with human perceptual rules) to create a good design. Those who rely entirely on a goal of good bench specs tend to make lousy sounding equipment.