If you're using mid to high end ICs then putting in a lesser quality Y-connector would indeed degrade the sound quality to the extent of the qaulity of the Y-connector.
Most any cable manufacturer will make up an IC for you with one end to the preamp and two to the amp. Of course, it would cost somewhat more but most all the major brands will do it as a special order.
This is the route I would suggest if you have upper mid to high end ICs and components.
Most any cable manufacturer will make up an IC for you with one end to the preamp and two to the amp. Of course, it would cost somewhat more but most all the major brands will do it as a special order.
This is the route I would suggest if you have upper mid to high end ICs and components.