miab wrote: > Thank you John. You have always been a great help. > > I currently am using my Touch with tt3.0 but I would love to be able to > use/see the screen as now it is disabled. In particular have you or > anyone else noticed a difference with or without the screen on the usb > output? > > John, you mention using a dac with both spdif and usb inputs. In your > experience which were you able to get the ultimate performance on, usb > or spdif? I'm guessing that it might be particular to each dac used and > the quality of their different inputs but what were your particular > experiences? Ultimately I assume that usb might have the edge if both > were properly implemented. I plan on using a USB to SPDIF converter into > my favorite spdif only dac BTW and I think the spdif out of a converter > might be better than spdif out of Touch.
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. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=94512 _______________________________________________ Touch mailing list Touch@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/touch
