You don't want to overload the input of your preamp. You have to adjust them in case they disagree with the preamp about 0db. A lot of digital output 0db is ~20db to loud for an analog input that is designed to have headroom. However the argument from the digital side would be that it reaches the maximum headroom only when it's playing at it's very loudest.
You also need to consider the voltages they are sending/receiving and what they are expecting.
You don't want to overload the input of your preamp. You have to adjust them in case they disagree with the preamp about 0db. A lot of digital output 0db is ~20db to loud for an analog input that is designed to have headroom. However the argument from the digital side would be that it reaches the maximum headroom only when it's playing at it's very loudest.
You also need to consider the voltages they are sending/receiving and what they are expecting.