I was trying to help a fellow head-fier understand digital data transmission and what it meant in regards to their USB cable quality concerns. The original thread is here.
The issue came up that digital signals are really analog signals---to which I disagreed and provided an counterargument. Obviously, this conversation remained at a high level without getting into any actual details, and as a consequence, is full of broad sweeping generalizations.
Now, I didn't mean to step on any toes, and I know my limited humble experiences with hifi audio pale in comparison to Currawong's, nor do I know any actual industry engineers. Furthermore, Currawong suggested that there are some experience DAC designers and other experts around head-fi who may be able to assist my understanding.
I started this thread to open a dialog with the experts on the topic. I put the thread in Sound Science, because
a) I didn't want to derail the other thread with an emotionally charged debate (nor do I want there to be any emotional debating here!), and
b) I hope that it will be acceptable to ask questions and discuss the details at a higher technical level than acceptable in the other parts of head-fi.
The topic of digital signal transmission and effects on perceived audio quality has been debated numerous times throughout the head-fi forums and there is an epidemic of misinformation floating about. It seems like it would be extraordinarily beneficial for the community to get the fundamentals straightened out and organized in a way that can be explained to the less technically savvy.
Thus, I propose this conversation to be technically slanted and rigorous with the goal that those with technical backgrounds can follow sufficiently. Once the underlying principles are established, the basics should be boiled down in a way that is accessible to all.
I would have proposed using the ODAC as a case study because there is a freely available schematic; unfortunately, the USB controller datasheet is not publicly available, which leaves a pretty big hole. Any ideas for a DIY or open source asynchronous USB DAC that would make a good case study?
We could do case study on something based off of a C-Media CM6631 [datasheet]? Is it necessary to include the i2c link from the USB controller to the actual DAC as part of understanding where things can go wrong because of USB data transfer? As far as asynchronous USB controllers go, how much variability is there between models in their susceptibility to error because of USB data transfer conditions?
Basically, how is data communicated from a computer to an external DAC via USB and where can things go awry in between? What conditions are necessary for optimal DAC performance? What conditions are sufficient for optimal DAC performance?