Demian Martin skrev: > > Magnus Danielson wrote: > >>> The digital link in question is S/PDIF; with the current popularity >>> of Home Theater systems cheap cards with digital I/O have become >>> quite prevalent. As an added bonus, S/PDIF can be run over both >>> coaxial and optical media, the latter being attractive in further >>> isolating PC noise from any measurement setup. And of course, a >>> manufacturer's evaluation board is much better documented and more >>> suited to measurement-specific mods than a random sound card. >> The optical link commonly being used for S/P-DIF is TosLink and it seems >> like it can be the cause of many problems. It seems like some care in >> doing the optical link setup is needed. I have never digged into why the >> optical links have that problem. I can only guess, but bad optical >> coupling seems reasonable. The multimode "fiber" seems to be leaving one >> or two things to ask for. >> >> Cheers, >> Magnus > > Without getting too "audiophile" there are several considerations. Toslink > is bandwidth limited- the LED's are not really fast enough for 96K and > really not for 192K sampling. The effect is high jitter on the link or a > lost connection. The high jitter may not matter if the sampling is done with > the external capture system (most of which are much more expensive). SPDIF > or AES/EBU don't have the bandwidth limitation but can have other issues.
I think you meant to say the electrical S/P-DIF and AES/EBU. > The cheap ones don't have transformer isolation, however the transformers > can increase the jitter on the link. Depends on the transformer. The AES-3 electical form of AES/EBU (balanced on XLR) has a drawback in that it may be hooked up over lines, patchfields and cross-connects not intended for AES/EBU signals. This can cause some grief. Installation standards has changed as a result as a consequence. For smaller systems may the transformer not be as much of an issue as in larger installations. The unbalanced form of AES/EBU, AES-3-id, is becomming popular. It should not be confused with S/P-DIF since it is distinct in several forms, except for the obvious difference in subcode content. > You can use external USB capture, I'm > playing with an EMU Tracker pre gadget that seems to do 192K at 24 bits > pretty well and for $125. But I get better results from the ESI Juli@ pci > card for around the same price, very low distortion and noise, and good Alsa > support in Linux. It may be all that's needed. It is. Wordclock input? Cheers, Magnus _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.