...The reason why it was such a problem in soundcards was because of the proximity of the AD/DA to the CPU. ...the EMI emittence problems we experienced with having our ADC's a few inches from a super-high-frequency device with no magnetic shielding...
Yes, I understood your concern. As I said, I saw it bandied about on the web for years and years. I just never saw any evidence that it actually existed in any of the systems that I or my friends bought or made. Indeed, we tended to use better motherboards (which means better shielding, and if we assume that all interference came soley from proximity to the CPU itself, we are ignoring other potential paths...the inside of a computer is hell in that regard.), and better sound cards. I was into the DAL CardD and CardD+ and daughterboard early on, which had internal converters. RME has had internal daughterboard converters for many, many years. Lynx. Digigram. Mixsteam. The list of cards from 10+ years ago with internal converters but no EMI or RFI problems goes on and on. I can't talk about what might have occured with lower priced options because they are simply out of my experience.
I am curious if it exists as a problem today though. Just from a 'hey, I remember that problem!' standpoint.