We are currently prototyping a 2-parallel RCA cable.
The other day, I completed two types of cables with different signal conductors.
The copper wire for the signal line is of two types: C1011 (4N-OFC) and our general-purpose OFC, and both are configured as two parallel, single-core shielded wires. 
We will now begin processing the device, but we will decide whether to release two types as they are, or combine the best features of both into one.