On Tue, Sep 18, 2007 at 03:50:04PM +0200, Clemens Ladisch wrote: > John Rigg wrote: > > On Tue, Sep 18, 2007 at 10:07:05AM +0200, Ludovico Verducci wrote: > > > As far as I know the delta family boards drivers support the > > > synchronization of up to 4 audio boards over PCI: at the moment I'm > > > reverse engineering the hardware trying to understand how this can be > > > accomplished. > > > > I'm aware that some Windows users are using several Delta 1010s > > without external sync, but I'm not sure how it is done (or how > > good it sounds). AFAIK it would require a VCXO so that the frequency > > of the card's clock could be varied by enough to keep it in sync > > (ie. making the clock oscillator part of a phase locked loop). Looking > > at the PCI card on the 1010, I can only see standard fixed-frequency > > crystals. The only PLLs appear to be the internal PLL in the S/PDIF > > receiver and the 4046 PLL chip for the word clock input signal. > > In theory, it should be possible to use the PCI clock (between 25 and > 33 MHz) as input for one of the PLLs, probably after dividing it down. AFAICT neither of these PLLs can receive an input from the PCI clock. The S/PDIF receiver only receives a signal from the S/PDIF input, and the word clock PLL only receives a signal from the WC input in the breakout box (via a pulse shaping circuit to clean up the waveform). Apart from that, neither of these PLLs is particularly good at removing jitter (and I'd expect the PCI clock to have a high level of jitter), so quality would be reduced. John _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
