Imagine for just a moment that you were the designer of the Magic DAC. In this Magic DAC you had a normal digital audio input stage and its output fed the analog converter inside the DAC. Simple enough. But you realize as soon as you put jittered audio data into your DAC, its analog output sounds pretty bad.
Most DACS suffer from that very problem. But your DAC needs to live up to its name; Magic. And the magic is going to be a cool and wonderful module you place between the input and your analog converter that makes sure no jitter reaches the converter. It's magic! Only, there's a problem. After you get rid of the jitter presented to your converter stage, the sound is better but not perfect. How could this be? You're eliminating every bit of jitter before the converter. Where's the problem?
The problem is the power supply. It's easy to think of our equipment's functional blocks as little islands without any connection to the real world. But truth is, all systems are interconnected. And that's a problem.
Every time your Magic DAC's input takes in a bit, a small ghost-like copy of that bit appears throughout the entire DAC, courtesy of your power supply. And if that bit comes into your DAC a little later or earlier than expected, our sneaky little ghost-bit follows exactly in synch and pollutes the music with its remains. Thus, the more jitter, the worse the sound.
So our DAC isn't quite living up to its namesake just yet. Let's see if we can get it closer tomorrow.