13 Nov
2009
13 Nov
'09
6:15 p.m.
On Fri, 13 Nov 2009 22:37:33 +0100
fons(a)kokkinizita.net wrote:
On Fri, Nov 13, 2009 at 07:56:13PM +0000, Folderol
wrote:
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.
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,