I’m buying a new sub-woofer cable to connect the atom to a n-sub.
This cable has a single plug in one side and a double plug in another side
I think to connect the side with the 2 plug inside the preamp output of the atom and the side with 1 plug on the n-sub using the mono line input. Is it correct?
A single connection to the N-Sub mono input will work, although the intended connection method is to use a stereo connection.
Alternatively use a high level connection which you may find gives better sound quality. All you need is some cheap, thin speaker cables.