A couple of readers have asked a good question. "A digital recording of a live event doesn't always sound as good as an analog recording of the same, yet you say a digital copy of that analog recording ALWAYS sounds identical. How can that be?"
This is a really interesting area and the answer might not make a lot of people happy.
The quick answer is that analog has limitations greater than digital and it is precisely those limitations that cause us to like analog more than digital. Analog is already preconditioned in terms of frequency, noise and dynamic limitations that we have come to expect and - it turns out - seems more real to us. Making a digital copy of something that is already limited is easy to keep identical and without any further degradation.
Let me give you an example using film and video. Both film and video capture motion with a series of still images strung together that, when played back at a high enough rate, look to be moving. Film stops and starts 24 times a second, while video is nearly three times faster. Therefore, you might suggest, video is superior because it should be closer to not missing any of the fast action. But most people (including me) don't like the look of original video when the camera pans from left to right because there's less blurring of the images when the camera moves - as happens with the slower capture film method.
It turns out that film, although technically worse at 24 frames per second than video at 60, looks more natural to us because that's what happens with our own eyes. Try staring straight ahead and then, without blinking, move your head 45 degrees quickly. Note that when you do this the in between images are blurred. This is because our eyes really aren't continuous, just like film or analog aren't really continuous.
So, when we watch film and the camera pans, the in between images blur and it looks natural to us. When a video camera does the same thing, it does not blur in the same way and it looks unnatural to us.
BUT! Imagine now that we make a video (digital) copy of the original film. We capture perfectly all the blur of the original and then when played back over a television, the digital copy looks identical to the film. All the imperfections of the film are perfectly captured by the digital process.
The same is true for audio, analog and digital. Because analog (which is not a continuous process as many believe) comes already bandwidth and dynamically limited, it is easy to make an excellent ADC to digitally copy it - because the copying technology exceeds in every way the parameters of the analog master -just like in our film example.