Explain what you are trying to do and what equipment you are using and I will try to help. As I remember the CD3 has both balanced and single ended outputs so you can use either. What preamp (I assume) are you trying to connect to it? The preamp does not have balanced inputs?
In general their is an advantage with balanced cables when both pieces of gear are fully balanced. There are also other reasons like long runs of cable.
The BLs were designed to be used with the LS5 which had only balance inputs.This way you could still use your CD player or other single ended source. At that time Audio Research was moving from single ended to balanced on some of their gear.