I've read conflicting things re optimal cable length for digital cables, though expect it depends very much on the application. The main variable I've found for clock cables at least of which I've tried five is cable quality (conductor, shielding and termination quality) rather than length per se.
@kereru Clock or other digital cables are not the same as HDMI cables for i2S as per my last post. For example, a digital interconnect is best at 1.5m, whereas that would kill an i2S signal. The i2S signal is a different animal entirely and extremely sensitive to cable length. Try the 1 foot cable and see what you think, or try the 6” cable I linked above for only $5.50. Interested in your thoughts.