Does the length of the Cable matter?

cleeds

thanks for the clarification. Is the construction of a balanced cable more resistant to interference than a typically shielded rca cable, that was my assumption to suggest the conversion.

Over the years, I've used long and inexpensive rca cables, even 25lf to reach a sub, with no hum or problems, so I think OP should be ok. 

Properly grounded and shielded, and you'll be fine at 15 ft. 

Big mistake will kill sound quality.