Clock related question for Ted maybe?


#1

Been upgrading my Oppo 203 (i2s output and more) to make the most of my Directstream Dac, and have a question for someone more technically minded than myself RE: a master clock upgrade for my 203?

Thanks.

Been reading as much as I can here about the way DS works (ignores) clocks of anything digital plugged into it, and as such, Ted has mentioned whats more important in the case of Directstream is noise rather than incoming clock accuracy.

Have the spec sheet of the upgraded clock being used in my Oppo upgrade board, wondering if I could get a tech’s opinion on noise levels, measured performance in relation to its use in Directstream?

Clock data sheet here:
http://www.sbtron.co.kr/korean/product/pdfs/ocxo_sboc_25_sine.pdf

Thanks guys.


#2

Almost anything is better than the stock clock (it takes minutes to get within 100ppm of the longer term frequency (!?) Perhaps there’s some reason for that behavior, but if there is, it’s not obvious to me.)

Comparing to the DS’s clock might not be fair, the DS’s clock is expensive.

Anyway what you want to look at is the phase noise plot (note that the horizontal axis start at different values, it may be easier to read the table in the upper right of the Crystek part) The part that matters most is between 1 or 10 and, say, 1k:


#3

Thanks, that’s a good comparison.

The SBOC-25 doesn’t look TOO terrible if I’m reading the noise graph right?
Phase noise seem ok in the scheme of things you think?

The DS clock measures really good, wow.


#4

I’m pretty sure you’ll like the upgrade that you have. One of the upgrades that PS Audio did for the DMP over its Oppo base was the clocking system.

The thing about phase noise is it’s convolved with all of the audio and basically widens any given frequency by the phase noise plot on each side (scaled for the amplitude of the audio) So on an spectrum plot instead of a vary narrow peak for each frequency you end up with more of a triangle or an upside down Y shape for each frequency. Here’s what a lower phase noise (green) vs a higher phase noise (blue) could look like:


In audio you’d likely never see phase noise that wide or that high, but you get the idea.


#5

Thanks Ted,
Good stuff.