Originally Posted by
alphaGT
Digital playback from CD’s, (and I assume audio files too?), is not perfect. It is not 100% accurate, and there is no second copy on a CD to refer to for error correction .
Let me try to paint an analogy. You have a large block of wood, waist high and just as long, and it is cut into a bunch of peaks and valleys, like a Musical signal roughly. You measure it, it’s anchored to the ground so you can’t take it with you, so you make measurements of the peaks and valleys. You go back to your shop, you take 1x4’s and stack them against each other vertically. Trying to get as close to your measurements from the original. You can only be accurate every 3/4 inch, as that’s the thickness of the boards. So, you have built your copy, but the edges are all stepped up and down every 3/4 inch. What do you do? You take a jig saw and cut the leading edges off and make it smooth! Nice! Just like the original! But you take it to the original and place them against each other, and you find that all of your averaging has made a copy that is not accurate. The peaks and valleys are near the same place, but the edges are all different. It feels smooth to the touch! And if you couldn’t see them side by side, you’d swear they were identical. But, they are not. And of course the higher the resolution, if you went back with half inch boards it would be a little closer, and if you made it from eighth inch boards it would be even more accurate! But, on closer inspection, you still have tiny differences. There is no way to make an exact digital copy of an analog wave form. Out of wood, or out of electrons.
Don’t get me wrong, you can get VARY close! And these errors in shape do not sound like distortions, they sound like music! They are smooth on the edges, music flows! It doesn’t create noise. But, it is still ever so slightly different from the original.
Analog, I took a cardboard sheet and laid it up against the original wooden peaks and valleys and traced it, built the copy, and laid the cardboard on it, and traced it, and made an exact copy. I can take it back to the original and lay them up against each other and they will match! I’ve always thought of it as, analog is like looking in a mirror, while digital is like looking at a photograph. Maybe that’s an oversimplified view?
Russell