Originally Posted by Victor
This is the obvious reason why USB>SPDIF crutch wouldn't work well in such application: the entire thing should be slaved to video or it wouldn't work.
We use the USB solution for music only. For video, you have secondary issues of compatibility given the non-secure aspect of the USB path. So HDMI is the solution there, good or bad.
|Even separate audio-only master clock will not help: you'll need to resample audio in such case or it will run out of sync.
I am not following this one. You mean in the context of USB audio on a PC? If so, the PC becomes a data pump and not running synchronously. So no resampling is needed.
|I also can't understand the logic why adding properly designed PLL is overly complex decision, but adding $900 USB->SPDIF converter is just fine.
I share the quandary with you
. Here is the situation. I have added these converters to some of the best processors: Mark Levinson Dac/Processors and Berkeley Alpha DAC. I have added them to cheap boxes like Peachtree Nova. I cannot explain why it makes a difference up and down the tiers and why so much. I still remember the first time I tried it on the ML DAC. I had to switch back and forth to believe the difference.
The audiophileo also has a jitter simulator and triggering that even on the high-end processors changes the sound. Why would it if all the jitter is squashed out?
If you talk to Michael Ritter at Berkeley, he will over and over emphasize how you need the absolute best digital source to make their DAC sound good. I remember challenging him on that. After all, you think if you got a high-end DAC, you wouldn't need to jump through hoops like this. But according to him, you did if you wanted to get world-class sound.
Maybe some of this is due to secondary effects. That your PLL circuit itself is causing jitter elsewhere as it tries to do its thing. After all, the PLL is trying to eliminate the jitter from the source. It is not doing anything for the intrinsic clock jitter on the DAC. And when source jitter occurs, maybe the actions of its phase detector causes degradation elsewhere.
Maybe some of this is due electrical isolation offered by these converters. Clearly jitter is not the only reason audio fidelity is impacted. Perhaps cross coupling the systems without isolate degrades PLL or DAC performance.
We have the new Berkeley USB to S/PDIF converter on order so I should be able to test this effect more broadly.
This may be one of those situations where we confirm the observation and then work backward to find an explanation.