John - I've never heard of that calculation before and it's either accurate or some incredible double-talk.
Does it take into account shielding from EMI sources and is it network-centric (assumes twisted pairs)?
Your calculation would have to take being a 44.1
two channel signal into account, effectively halving the length at which one starts getting concerned about impedence... and by the time you get into multichannel, that maximum cable length is pretty short... also, since it's a serial and not a parallel connection, wouldn't you immediately also have to multiply by 16 (for bits per sample)? If both of these are correct - that would make the longest run without worrying about impedance 40'/2/16 = 15 inches.
Again, we're talking a difference of a few bucks. Even if just for piece of mind... splurge!
Bren R.
