I’m setting up a new computer that will live in the music room and be used for, among other things, ripping vinyl with my NPC. This computer has an audiophile SOtM USB card and some generic USB ports from the motherboard.
Right now I’m planning to use the SOtM card for playback to the DAC and plug the USB cable from the NPC into one of the standard USB ports. My thinking is that higher quality USB cables and such do affect playback, but that the generic stuff should be adequate to accurately record the bits output by the NPC’s AD converter onto my hard drive.
Aside from not wanting to spend money right now for another good quality USB cable, in my setup it’s a real pain to get behind and switch cables every time I go from recording to playback, so I’d prefer to avoid this and can do so if I utilize the standard USB port for input. If anyone can give me reasons why going the less convenient route would result in better quality rips, I am all ears!
I think that you have the right idea there. While it may be possible for a fancy audiophile USB cable to affect the quality of a digitized needle drop I personally SERIOUSLY doubt that it would. In this case the analog domain is in control and once you enter the digital domain you are truly digital and ‘bits is bits’… 
Your planned setup is the way that I would do it.
J.P.
Then again, I have been proven wrong before… 
J.P.
So why going the other way, computer to DAC, with a better cable improve SQ ?
It’s certainly not impossible that the cable from the NPC would affect the SQ. If I had unlimited resources I would have everything of the highest quality. Right now I’m dealing trying to figure the best way to deal with some limitations.
Here’s one analogy that might work, or it might not.
Imagine a wholesaler who deals in widgets (= bits of audio data). The conveyer belt from the delivery area to the warehouse is old and rickety, but it doesn’t actually damage the widgets and doesn’t make it any harder for the warehouse workers to stack the widgets (= storing the file from the ADC on the hard drive).
Then the widgets get sent from the warehouse to be shipped off to retailers. As they move, they need to be scanned, sorted, and packaged for shipment (= bits being converted to analog). If the conveyer belt from the warehouse vibrates a lot or does not run at a constant speed, the scanning is inaccurate and the packing machine messes up some of the bundles (= a poorer quality analog signal). That’s how I think of it, anyway.
I see it as going from analog to digital, the analog is ‘pure’ and the ADC is in control and defines the quality of the converted signal. Essentially, the analog is in control. Timing is critical in the conversion process but is solely dependent on the quality of the clock. Once in the digital domain there is no jitter or distortion. There can be data loss or corruption but that should be flagged by some error checking mechanism and can sometimes be corrected. There should be no feedback mechanism where the outbound data path (USB cable) should be able to affect the conversion - the conversion is already done.
When going from digital to analog the digital domain is in control. The process of conversion is not as simple as it seems as timing is critical and signal artifacts in the digital domain seem to affect the conversion even though the data is correct. All of these digital artifacts are present BEFORE the conversion is done thus can affect the conversion. Now: how signal artifacts on the input of a buffer can affect the timing of the output is beyond me, but obviously there are some subtle mechanisms at play here.
Again, I could be proven wrong but I just don’t see how the signal path exiting an A/D conversion device is likely to affect the A/D process that has already occurred. once in and within the digital domain, as long as the digital data is delivered without error then the quality of the pipe (or cable) should be of no significance.
J.P.
@wingsounds, that’s pretty much what I was trying to say with my little analogy; you put it much better.