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Optimal length(s) of a digital aes/bsu cable

I have an option of a high end cable (0.6m) as a digital interconnect between a Berkeley USB and Reference DAC. I’d rather have a short cable practically speaking as the boxes sit next the one another but I also want to maximize sound quality (of course.)
i have read in agon that I should go with less than 1ft or >1.5m. That was with spdif but what about aes/bsu? Does that have a different dynamic, being balanced and all?
Thanks!
128x128johnmc67

Showing 2 responses by kijanki

kijanki's avatar
kijanki
4,410 posts
 
It depends on the output transition time .  Without going into details, it is roughly transition time divided by 20.  For typical 25ns transition it has to be longer than 1.25m.  The problem is that transition time is unknown (and almost impossible to measure) and can vary from 5ns to 50ns.  The main concern is that refection from the end of the cable will distort transition at exactly threshold point.
kijanki's avatar
kijanki
4,410 posts
 
Being balanced doesn’t change anything. Your cable might not be optimal length, but these calculations depend on many factors, like output transition time of the source, signal propagation speed in the cable etc. Also, this cable might be a perfect characteristic impedance match in your system (no reflections at all). The best way is to borrow one and try. Your ears will be the best judge. Mismatched cable induces time jitter of digital signal, that translates as noise added to music (not present without signal/music). This noise will make sound harsher, brighter with possibly worse imaging.
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