Now the problem is definitely not jitter from the source - my DAC's can tolerate 2uS of jitter and it will have zero difference to the measurements - also the USB is isochronous asynchronous so the timing comes from the DAC clock, so source jitter is not a problem.
So I looked into the issue of different SQ with sources and found two sources of error:
1. RF noise.
2. Correlated current noise.
So the solution to the above problems is galvanic isolation. This means that RF noise from the source can't get into Dave, and small correlated currents can't get in too. And this approach gave two benefits - much smoother sound quality, and a deeper soundstage.
Now with Dave I can no longer hear which source is connected, but before without the galvanic isolation it was easy to hear. Additionally, optical sounds almost identical to the USB, as optical is clearly galvanically isolated too.
关于USB链接不同电脑或数播音质不同：
我的解码可以容忍高达2uS的jitter，而测试结果并无不同。异步USB意味着时钟基于解码，所以音源Jitter不是个问题。
我觉得不同转盘音质不同，主要源于音源产生的两类干扰：射频噪音和相关电流噪音。
解决方式是做电气隔离，之前没有隔离的机器（Hugo等）能轻易听出音源差异。另外，光纤与USB的音质几乎等同，也是因为光纤显然能做到电隔离。（他曾说平衡数字线路是造成音质问题的原因之一，所以DAVE多达四组BNC数字输入，两组光纤输入，而只有一个AES口）。
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发表于 2018-11-19 23:52
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