I started this because I was using the upsampling built into Squeezelite(libsoxr), not using SoX in LMS so I can't offer any clues as to how to get that to work properly. The Squeezelite resampling option is not the same as in SoX the program arguments, although the underlying code is the same.
The one I'm using right now is mI:::28, which is medium quality, intermediate phase and 28 bit depth. I'm not quite sure exactly how this translates to SoX arguments. The upsampling is done in Squeezelite on the Wanboard and then sent to my own USB DAC, which uses a standard XMOS UAC2 interface, I2S is run through isolators, on isolated side are low jitter clocks, reclocker and the DAC chip is PCM5142 with very low noise regulators on all of this. The low jitter clock is sent back through an isolator to the XMOS interface. The PCM5142 has several builtin filters, some of which are better than others. If you feed it 352.8/384 it turns off the internal filters. So by using resampling in Squeezelite to 352/384 I can bypass the implementation in the chip and just the software. Even if upsampling to a lower rate it can still be advantageous, upsampling to 88.2 with the above paramters is a significant improvement. Going to 176.4 is even better but the best canbe achieved by going high enough that the built in filters are completely bypassed. In all these cases the network traffic stays the same, but the USB data rate goes up since the upsampling is being done in squeezelite. I have not had time to go into depth trying all kinds of different parameters, I spent a few nights trying different things and came up with the above. I've been listening to it for some time now and am still enthralled with what it is doing. BTW the load on the Wandboard processor is about 8% when using this setting. When using the default 20 bit setting it is about 4% and when not doing any upsampling its about 2%. Klaus, to your statement that upsampling should not be necessary, the answer is of course YES. The issue is that as far as I can tell all DAC chips with builtin filters are compromised sonically, the upsampling is an attempt to bypass these filters with an external filter that is more sonically "transparent". So yep it IS a band-aid, but one that is currently necessary for most DACs. If the internal filters are not disabled, exactly how the internal filters interact with the external filter are going to be very DAC specific. In the case of the chip I'm using the filters get simpler as the sample rate goes up so even though they are still there if you upsample to an intermediate rate, the total result sounds better than the builtin filter going from 44.1. The best sounding parameters for going all the wayto 352.8 and 88.2 will almost certainly be different, but I have not explored it yet. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=99088 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
