Thanks for the kind words Greg. You also brought out some valid points that i forgot to mention. As such, i hope that you don't mind that i highlight or expound upon them a bit. I've tried to keep this "simple" so most folks can follow along. If i've oversimplified or stated something that needs correction or further clarification, PLEASE do so : )
Since wide bandwidth circuitry can respond faster, the difference between peaks and quiet passages seem even more drastic. If there is no signal present or notes that are spaced apart from each other, the circuitry can drop back down to "zero" and come back up to full output fast enough to show just how "separate" each note really is. This is what separates "average" components from those that have a "really black background".
Having a "blacker background" gives you higher resolution and the ability to more easily listen "into" the recording i.e. able to hear smaller details that are otherwise covered up. They could be covered up either by a higher noise floor or due to signal loss as the slower, "unprepared" circuitry TRIES to respond to each and every dynamic contrast as it occurs.
Some of the losses might be attributed to what is called SID or Slewing Induced Distortion. Slew Rate is what measures how much voltage can be passed in a matter of a phenomenally short period of time. This is expressed in Volts per Microsecond or V/uS. A higher figure is always better ( in my opinion ) with 350V/uS* being "better" or "faster" than 35V/uS. Think of slew rate as being how much amplitude signal the circuitry can develop at the drop of a hat.
Rise time is how fast a circuit can respond from zero to a given level of ( rated ) output. It is also a sign of how fast it can respond to dynamic changes, so a lower figure that takes less time is always better. Like slew rate, it too is also measured in microseconds ( uS ). A figure of .01 uS* is more desirable than a figure of 1 uS given the same level of output.
A shorter rise time also (typically) signifies that there will be less ringing or that the circuitry has "good brakes". This is called "fall time" but most manufacturers don't publish such a spec. Think of rise and fall time as a car that can accelerate like gangbusters AND stop on a dime. After all, such is the nature of music.
If the signal is so "dynamic" that the circuitry can't respond fast enough or in great enough amplitude, the circuitry will:
A) lose some of that signal's resolution B) introduce distortions of its' own to the signal. Obviously, both of these are "bad things". That is why one would want to have BOTH a low rise time ( to respond quickly to the signal ) and a high slew rate ( to produce enough volume to handle all of the signal ).
In order to better understand what i mean, think of the way that a fast, speedy and organized person and a sluggish "i'll do it later" person respond to tasks. The person that rushes to get things done at the last minute overlooks small details ( that can add up to major repurcussions ) simply because they don't have the time that it takes to look at every aspect of what they are doing or involved in. Not only are small details left out, but the quality of the main task also suffers. On the other hand, someone that is speedy and efficient can actually do more work of higher quality without getting "slowed down" by details. In fact, if they are truly fast and efficient and beyond the task presented to them, the small details will become even more apparent without them running over the main theme of the task.
Would you rather have your audio system performing like a well trained professional or a "shlep" ??? Obviously, these are two extremes and most equipment falls somewhere in-between. Where you draw the line should be done with your ears though and not with a sheet of specs. Hope this helps Sean
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* These figures were taken from one of my preamps and represent pretty "fast" equipment.
