On Fri, 13 Nov 2009 22:37:33 +0100 fons@xxxxxxxxxxxxxxx wrote: > On Fri, Nov 13, 2009 at 07:56:13PM +0000, Folderol wrote: > > > The effect you can get with a system with poor stability but very strong > > locking when incoming pulses are half way between the wanted times > > (used to happen a lot with early discrete PLLs). The system will > > alternately lock on the early and late pulses. The correction waveform > > looks like a cog railway :) > > - To generate a clock that is good enough for audio sampling you'll > need a analog PLL based on an Xtal oscillator, and with less than > 1ns (nanosecond) jitter in the audio BW, and preferably even less. > > - All AD converters require a clock that is much higher than > the sample frequency. For example the TI ADS1278 requires > 27 or 37 MHz. > > - If you want the soundcard to lock to a reference provided by > the master (PC), all you have is the timing of Ethernet > messages. For example the PC could send a message every > millisecond. With the above clock frequencies that would > mean a PLL multiplier with a ratio of 27000:1, somewhat > more than the 1:1 you seem to assume. It would need a BW > of a fraction of a second. Can be done, but not simple. > > Ciao, I fully appreciate what you are saying here. I have been largely thinking out loud, and also mostly in the digital domain where timing variations can be far more coarse-grained. The fact there is software out there that enables collaboration via the internet demonstrates that it is do-able. We just? need to think out how it can be done with as simple hardware as possible :) -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
