Optimal length for digital cables: 1m or 1.5m?

the length that 'supplies' sufficient rated impedance.

Mea culpa Al! I meant between my Cary 306 that I use as transporter and the Eastern Electric MiniMax DAC Plus (which fortunately has the BNC connector as well). Thanks for the link.

If I may ask you a similar question but for the analogue signal xfer: assuming that there is no impedance mismatch between the preamp and power amp, how short can a RCA interconnect be?

I agree with AL. A friend of mine and I have a/b'd a 1 meter Shunyata Zitron Python digital cable and a 1.5 meter Moray James cable and we both preferred the Shunyata cable but we both understand this does not answer your fundamental question. I faced the same cost conundrum you are considering and opted to spend the extra money elsewhere in my system. The only way to know for sure is to compare the two lengths of the same cable with the same equipment, IMHO.

If I may ask you a similar question but for the analogue signal xfer: assuming that there is no impedance mismatch between the preamp and power amp, how short can a RCA interconnect be?

If the goal is to minimize the sonic effects of an analog cable, the shorter the better. That may not always be subjectively preferable, though.

The technical factors that are involved in digital signal transmission, and in analog transmission at audio frequencies, are very different. The result being that length considerations for the two kinds of cables are also very different.

I should add, btw, that if a very short length is practical for a digital cable, such as 6 to 8 inches or so, that would often be a good choice. It is the intermediate lengths, that are significantly longer than that but significantly shorter than 1.5 meters, which stand the greatest chance of not being optimal.

Regards,
-- Al

if a very short length is practical for a digital cable, such as 6 to 8 inches or so, that would often be a good choice.

That's interesting info!
Thanks