Any thoughts ?
I tried to find a simplified video of it but could not as they are all done for engineers.Thanks Smokester. The reference was "Eye Opening" Interesting, but over my head technically.
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In digital audio and USB, reliability is never a concern since we are dealing with strong signals and short transmission lines. As such, it is a mistake to look at the eye pattern and sweat over it like communication engineers normally do in much more severe cases.
The CD players in the 80s were asynchronous? good to know.
As a kid, I had put my thumb on the spinning LP to see what happened. LP playback, being "synchronous" gave immediate feedback. So did Dad if he were listening to Tennessee Ernie.
When I first opened up a CD player I just had to repeat the experiment. Nothing happened (at least for a while).
Playback is asynchronous with respect to the short-term spin of the CD. Spin, read ahead, keep a buffer filled, then the clock dribbles collected data through the conversion to analog at a steady rate.
Someone here went on to explain that not a single bit of data on a CD makes it to the DAC, anyway. The data on the disk is not the left-right sample values.
See
https://en.wikipedia.org/wiki/Cross-interleaved_Reed–Solomon_coding
https://en.wikipedia.org/wiki/Reed–Solomon_error_correction
The master clock may disagree with you.
I haven't seen it and cannot find it. Can you provide a link to the blog or was it somehow misplaced in the forum upgrade?Dennis,
You should read my blog in CA about CD playback.
Correct in the case of mass market CD players. Regardless of what buffering goes on in the CD player, ultimately the "platter" is the master. The clock that drives the DAC will attempt to sync up to speed of the bits coming from the CD transport and as such, its jitter will travel to the output of the DAC. It is not a complete pass through however. The PLL used to generate the DAC clock will filter the high frequency jitter components subject to its corner frequency. There were also ultra cheap CD players that used the clock from platter directly to drive the DAC (i.e. without the PLL filtering). Example of this was early portable CD players.The master clock may disagree with you.
Regardless of what buffering goes on in the CD player, ultimately the "platter" is the master.
It has to. Imagine if you used a fixed DAC clock. The platter would either fall behind or get ahead of it.I see no reasonable way those platters were providing clock.
That's correct but the amount of data also varies per track. Constant linear speed is used in CD (audio).From the hazy memory of my experiment, before the era of Data Drives, the platters I saw ran at obviously stepped speeds depending: fast at the center, slow at the edge. Several, not many, steps.
I believe CD spun at 450-500 rpm near the center and 200 rpm near the edge. It also maintained a constant linear velocity rather than working in steps.From the hazy memory of my experiment, before the era of Data Drives, the platters I saw ran at obviously stepped speeds depending: fast at the center, slow at the edge. Several, not many, steps.
I see no reasonable way those platters were providing clock.
I still have my first drive in the garage. Marantz 3 something? One channel of the analog output was only giving a half-wave (reason for retirement) but it probably still works. I'll drag it out and look again (likely before part 3 of REW for Dummies comes out).
(I get to be wrong, though, not being a member of Audio Royalty)