pippin;656591 Wrote: > The jitter discussion is not about lost bits. > The way SPDIF works (or better: as it was originally supposed to work) > the source (here usually the Squeezebox) drives the clock for the DAC, > NOT the device which does the actual conversion. Since the DAC is > essentially a low-pass filter (OK, I'm exaggerating but that's at least > it's filter characteristic) and low-frequency modulation in the clock > signal can end up in the final audio signal. > > Whether this is an effect that could actually be heard is debatable > because phase jitter is a HIGH FREQUENCY signal (if you look at it's > effect on filters), not a low frequency signal. > > The discussion is moot anyway these days because most modern DACs > re-clock the signal anyway (that is: they buffer the input and use > their own internal clock) so whatever happens before the DACs buffer > (unless, of course, it's about changing the actual bits) will be 100% > lost anyway so optimizing there is just a perfect way of completely > wasting your money. btw I love your work Pippin! Otherwise: I think we are in agreement, that is in effect what i was saying. The critical point is that the talk of the transmitting device "driving the dac clock" may lead to the supposition that the DAC has to convert the samples at a rate which is directly determined by the clock signal decoded fro the S/PDIF signal. It does not. At least AFAIK no competently designed dac has for a long time worked that way. I mean for heaven's sake we know the data is sampled at a sample rate of 44.1kHz, so why can't the data simply be decoded with a clock at that rate? Only becasue of a possible over-underrun of data: does that sound like an insurmountable problem?
Basically you can/do have a new clock in the dac which simply has to match the long term average rate of the transmitting device. I am not sure about the filtering point. AFAIK depending on its characteristics, jitter may present either as noise or distortion, and the frequency of the noise generated is not necessarily above the passband limit of the anti imaging filter. But we agree i think that jitter should be the jitter determined by the DAc's own oscillator. -- adamdea ------------------------------------------------------------------------ adamdea's Profile: http://forums.slimdevices.com/member.php?userid=37603 View this thread: http://forums.slimdevices.com/showthread.php?t=84742 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
