Digital Drive

Posted by John Marks (P) on April 05, 2016 at 12:35:10

In Reply to: RE: Maybe you could give us a Free taste? posted by Jeff Starr on April 04, 2016 at 20:57:06

To start with, people have to realize and accept that:

THE COMPACT DISC IS AN ANALOG MEDIUM AND IT IS READ BY ANALOG MEANS.

Period. End of story. The only zeroes and ones are not on the CD; they are in peoples' heads.

The laser that cuts the glass master (BTW, there have been at least 100,000 CDs pressed up in the last 26 years that say "JMR" on them) cuts pits or divots in the glass and those are eventually molded into the polycarbonate.

In order to give the CD player's laser something to "read," the polycarbonate has to be plated with something reflective--usually aluminum.

The difference in reflectivity between the smooth surface of the CD and a pit in the smooth surface creates a difference in the ANALOG output of the photocell that is the origin of the signal that, through processing, is DEEMED to be "digital."

As it turns out, the sharpness of the transition between a shiny reflection (CD surface) and a diffuse reflection (a pit) makes a big difference in the timing of the digital signal train. Remember, the thing that made the S/PDIF protocol economically feasible was that the timing signal was embedded in the music signal. Both a strength and a weakness.

The crystalline structure of gold (an amazing element--you can beat out a one-inch cube of gold so thin it will cover a football field) is more supple and ductile than aluminum. The gold folds over the edge of the pit more neatly, and so the transition time is shorter and the read is more accurate.

Now, feel free to ignore what I say and email John Atkinson and ask him to recall what he heard in my listening room about 5 years ago, when I played for him aluminum and gold JMR CDs made from the same stamper...

He heard a distinct difference. I don't think it made him happy to find out that gold made a difference, but, he heard it. He said that the ambient sound of the church fit in better with the sound of the violin. Or words to that effect.

jm