JohnSwenson wrote: > I have not noticed any case with a USB DAC where the screen on or off > made any difference. There certainly might be a DAC sensitive to this, > but none of the ones I tested were. > > The things that I found that made the biggest difference were scheduling > issues, thread priorities etc. These had the biggest difference in all > the USB DACs. (different DACs were more or less sensitiveto this, but > for any given DAC it was the most important). Buffer size was the next > important, and everything else made little difference. Again the > settings that were produced the best results with S/PDIF were NOT the > best settings for USB. > > I did not try any USB to S/PDIF converters in these tests so I don't > know how they performed. > > A USB to S/PDIF converter may or may not sound better than the S/PDIF > out of the Touch. There are two categories of paramters that affect the > results, one is ab solute and the other is relative. The absolute > parameters are things like jitter and noise, the lower the better. But > then there is impedance, the absolute value doesn't matter, what matters > is the matching between the transmitter and the receiver. Unfortunately > even though the spec says 75 ohms, the reality is that for both > transmitters and receivers the impedance varies all over the place, from > 15 ohms to over 120 ohms. If you run a transmitter with 15 ohms into a > receiver with 120 ohms you are highly likely to get poor performance no > matter how low the jitter on the transmitted signal is. > > So a given converter and DAC MAY sound better than the direct out, but > not necessarily because it is "higher quality", but most likely because > it just happens to be a better match to the input circuit on the > particular DAC. > > BTW USB has a similar issue, but the range of mismatches is usually much > less than for S/PDIF. (I'm not sure why, it's actually easier to get a > good match with S/PDIF, but for some reason most designers of S/PDIF > boards ignore the issue, but DO think about it for USB, probably because > with S/PDIF if you get it wrong it still works, but if you get the > impedance wrong with USB it doesn't work at all) > > As Guido said some DACs like the converter better and some don't. And > most likely if you tried a different converter you would get even > different results. > > John S.
John, Since I have your attention, do you think it's possible somehow to use an external computer dvd drive to spin the occasional disc somehow through a USB hub into the Touch and out from the USB hub to a USB dac? This probably a very silly question but I would really like to have the small form factor of an external drive in case friends come over with their favorite disc's. Is there some other way to make an external cd/dvd drive a transport short of having a computer hooked to it? ------------------------------------------------------------------------ miab's Profile: http://forums.slimdevices.com/member.php?userid=34270 View this thread: http://forums.slimdevices.com/showthread.php?t=94512 _______________________________________________ Touch mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/touch
