I got to thinking that DACs have buffers that they read from and realized that the upstream source shouldn’t matter, but they apparently do. Why doesn’t the buffer completely eliminate the relevance of the quality of the source? Are there types of DACs, like asynchronous DACs, that make the CD transport or computer source quality irrelevant?
It depends on the way the buffer works. The buffer in the Benchmark DAC3 for instance is not a resampler or a PLL receiver. I have not personally heard it, but customers have told me that putting my Synchro-Mesh reclocker ahead of it has no effect on it, indicating that it may actually reject most jitter. I have no idea how good these customer systems are however, so I may still hear a difference in my own system.
Making the source jitter irrelevant is a good idea, but only if the internal DAC clocks and circuits used deliver really low jitter also. This is in no way guaranteed. Those circuits can easily take a 1psec jitter spec oscillator and convert it to 300psec and they usually do.
This is exactly why I prefer DAC’s that have no reclocking on the S/PDIF inputs. This way you can drive those inputs with lower and lower jitter sources and reap the benefits.