Tom -- While I think that the term "crisper" can correctly be used to describe what is meant by "fast," Johnnyb53 is also correct when he says that "fast components have sharper transients and generally more space between the notes and therefore more clarity." Think of it this way:
Regardless of how "fast" or "slow" the preamp or amp is, the amount of time between the very beginning of one note and the very beginning of a subsequent note will not change. However, the amount of time between the very beginning of one note and the very end of that same note (or another note) CAN change, if the "risetime" and "falltime" (or, correspondingly, the bandwidth) of the component is sufficiently slow to attenuate the high frequency content of the signal.
It is well established that the ear tends to "latch on" to the leading edge of transient sounds, and give them disproportionate emphasis relative to what follows during some subsequent number of milliseconds. If the speed of that edge is degraded, the subjective result may be described as lack of crispness, dullness, poor definition, reduced clarity, etc. Similar subjective effects can occur at the trailing edge, if the output signal doesn't stop as quickly or as cleanly as the signal from the source.
The total duration of the track or recording, though, will not be affected significantly by any of this. The amount of time from the start of the first note to the end of the last note will only vary over an amount corresponding to the falltime degradation of the very last note on the recording. I think that will be clear if you consider the second paragraph in this post. That variation will be measured in microseconds (millionths of a second), or perhaps tens of microseconds -- in other words, totally insignificant.
6550c -- Slew rate and risetime/falltime are loosely related, but not quite the same thing. Slew rate is defined as the maximum rate at which the output signal can change, usually measured in volts per microsecond. Risetime is defined as the amount of time required for a signal to change from the 10% point to the 90% point of a positive-going step change in voltage. Falltime is similar, except that it applies to a negative-going step change in voltage, and is measured from the 90% point to the 10% point. Risetime and falltime inversely correlate with bandwidth.
I'm not particularly expert in this area, but I believe that with respect to audio components slew rate tends to be primarily relevant to "large signal" amplitude changes, meaning those that approach full scale (full power in the case of a power amplifier), and the idea is that the slew rate must be faster than the maximum expectable rate of change of the input signal, or distortion will result. While risetime and falltime can be relevant in the context of both small signal conditions (which typically comprise most of the music) and large signal conditions, and can affect the signal by limiting its bandwidth (i.e., by rolling off very high frequencies), as opposed to introducing distortion.
It is common for the full-power bandwidth of a power amplifier to be different than the small signal bandwidth, because different design parameters come into play under the two sets of conditions.
Rrog -- I doubt that there are many Audiogon members, or other audiophiles who are at least semi-serious, who "buy based on specs." However, that does not negate the value of having as good an understanding of specs as possible, for at least two reasons:
1)Ruling out potential component acquisitions that would be mismatches to other components in the system (gain mismatches, impedance mismatches, level mismatches etc.), or that would be mismatches to the listener's requirements (peak volume capability, deep bass capability, etc.).
2)Providing clues as to particular things that should be listened for when auditioning components.
Regards,
-- Al
