Der has a good point. The idea of not using an overly high input impedance is in order to reduce RF/EM or ground loop noise pickup from the audio connections.
Benchmark DAC1 Pre has a very low output impedance of around 30 ohms. The powerful drive capability of a preamp of this type will be such that it can drive extremely long runs on interconnects without any audible degradation effects due to capacitance. In contrast a preamp of 600 Ohms output impedance or higher may sound dull dynamically and even harsh especially as it becomes overdriven.
It goes without saying you should preferably be using a balanced preamplifier with XLR out but I assume you would not dare power ATC's with anything else.
Benchmark DAC1 Pre has a very low output impedance of around 30 ohms. The powerful drive capability of a preamp of this type will be such that it can drive extremely long runs on interconnects without any audible degradation effects due to capacitance. In contrast a preamp of 600 Ohms output impedance or higher may sound dull dynamically and even harsh especially as it becomes overdriven.
It goes without saying you should preferably be using a balanced preamplifier with XLR out but I assume you would not dare power ATC's with anything else.