Harman AKG C2000 Mode D'emploi page 15

Powering
In order to preserve symmetry, use 2 x Rv resistors with a maximum tolerance
of 0.5% only.
If the amplifier inputs are single-ended (grounded) or have no input
transformers, wire either capacitors or optional transformers into the audio
lines to prevent any current leakage into the input stage.
Adding Phantom Power to Unbalanced Amplifier Inputs
C2000 15