I know you want a balanced cable suggestion, but I don't have one as the amps I owned at the time I had my Opus 21 did not have balanced inputs. However, as Lazarus stated, the DNM is the way to go if you want to bypass the internal volume control of the O21. There is a DNM DIN-RCA cable for sale here on AudiogoN (I have no affiliation with the seller) that will allow you to use the DIN output (not volume controlled) and connect the other end to a unbalanced RCA connector on your pre-amp.
Since you mentioned that you use a pre-amp, I'm suggesting the above. I think the DIN output of the O21 is the only output that bypasses the internal volume control built into the O21.
BTW, the internal volume control is very good IMHO, but why have it in the circuit if you don't need it?
Like Lazarus28, I miss my Opus 21 and may end up buying one again in the future. It is a great bargain IMHO....
Enjoy,
TIC
Since you mentioned that you use a pre-amp, I'm suggesting the above. I think the DIN output of the O21 is the only output that bypasses the internal volume control built into the O21.
BTW, the internal volume control is very good IMHO, but why have it in the circuit if you don't need it?
Like Lazarus28, I miss my Opus 21 and may end up buying one again in the future. It is a great bargain IMHO....
Enjoy,
TIC