soundcard clock modding to improve S/PDIF jitter?

[ericj]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif well, all I can see is that Envy24 DSP and the M2Tech HiFace both carry 2 discrete clocks that are multiples of 48 and 44.1kHz...why would they have bother doing so if the Envy24 DSP could have gotten away w/ a single clock? it would have made their OEM customers happier. also the CMI8788 only has one 24.576Mhz clock...its datasheet talks about a max jitter of 500ps. first Asus released the Xonar STX using the CMI8788, then a few months later they added a CS2000 clock conditioner on top of its clock on the ST...and boasted on their website about much tighter jitter..I would even dare saying that the difference is VERY much audible between the 2 cards on headphones. then some ppl swapped the clock for a killer 1ppm clock from Audio-GD, and said that stereo imaging went up through the roof! anyway, I've found a CMI8738 board that has native coax...and it's dirt cheap, I like the sound of that...but I can't see a transfo. though well, jitter is a recently discovered problem...as Burson says: Low Jitter Clock

Burson is a charlatan of near-P.W.B. proportions. jitter at all stages of digital audio has been talked about for more than 20 years.

If the receiving end is re-clocking anyway, how much could it possibly matter?

 

[DaKi][er]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Your assumptions here are total nonsense. PLL clock synthesis has been the norm for 20+ years. They really can get 44.1khz spot on using a reference crystal that is not precisely divisible by 44.1khz. 'course, I think all clock upgraders (in sources younger than 20 years or so) are barking mad. And I won't be impressed until i start seeing crystals in ovens on these clock upgrades. Seriously, y'all talk like it's the bees knees, but nobody in that whole field seems to have paid any attention to what's been done about the problem of clock accuracy in, say, radio signal generation, where it actually matters rather a lot. How do you account for thermal variance in your uber-clock? come on, how? If there's a chip of quartz in there anywhere at all, it's going to behave differently depending on temperature.

The longterm accuracy means nothing at all, no one really cares that their clock plays middle c at 261.65Hz instead of 261.62Hz (thats 100ppm difference) but jitter or the proper term phase noise matters in the stability in the short term, where you care about the amount of jitter in the range of 1 to 100Hz about the carrier frequency.

High accuracy has nothing to do with low jitter. You want to know if these PLL's are any good for audio? Then what is the dBc @ 100Hz and 10Hz, as that is what matters

I'm not going to argue about the audibility of it, but it is certainly measurable in the final dac output and that is enough for me

 

[IPodPJ]

Quote:

Originally Posted by 12Bass /img/forum/go_quote.gif This is what you need: Antelope Audio

I would love to get one of their clocks. I have read nothing but good things about them. My problem, aside from not having the money

is that only my Transporter has a word clock input. My DAC does not.

 

[leeperry]

Quote:

Originally Posted by ericj /img/forum/go_quote.gif Burson is a charlatan of near-P.W.B. proportions. jitter at all stages of digital audio has been talked about for more than 20 years. If the receiving end is re-clocking anyway, how much could it possibly matter?

well, Audio-GD also sell 1ppm clocks, are they charlatans too?

I agree that if the receiver reclocks, it shouldn't matter all that much.

but in that epic thread, the guy says that even the cable matters

http://www.head-fi.org/forums/f7/usb...hiface-449885/

 

[Pars]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif well, Audio-GD also sell 1ppm clocks, are they charlatans too? I agree that if the receiver reclocks, it shouldn't matter all that much. but in that epic thread, the guy says that even the cable matters http://www.head-fi.org/forums/f7/usb...hiface-449885/

See DaKi][er's post. ppm is long term stability, and meaningless when it comes to phase-noise, or jitter. A good long term stability figure doesn't mean the clock is high jitter or low jitter, so it could still be a good oscillator. It just shows that the manuf. doesn't understand the difference, or is playing upon the marketing power of "atomic clock", etc. Probably akin to saying you use all 0.1% resistors... most times it just doesn't matter.

I thought much of Burson's stuff was made by Audio-Gd

 

[cobaltmute]

You can buy off the shelf parts that have better spec than the Burson for jitter.

That being said, you have to have a really, really, quiet supply to get those numbers however. 1/f noise and just above is apparently very important.