The C2 input is split through 150Hz -6dB/octave High Pass filter to feed the External Sidechain input. The C2 operates as normal, untill the 'External Sidechain' switches selected. (External signals can still be connected if required, with or without the filters)

Connection
One cable is used for each channel. The normal input signal is connected to the female XLR, and the 'straight through' male XLR is connected to the C2's input. This allows operation as normal. The 'High Pass s/c ip' male XLR is connected to the C2's 'External Sidechain Input'. This is a filtered copy of the normal input. When'External s/c' is now selected with the front panel switch, the new filter is engaged, and if deselected the C2 runs as normal. To use the filter in line with a different External Sidechain source, simply disregard the 'straight through' XLR connection.

Note that for the following filter performace, the 'High Pass s/c ip' cable is designed to feed an Sidechain input with impedance of 10k Ohms from each XLR pin to ground. (as in the C2 Compressor). Lower impedance inputs will result in a higher corner frequency, and vice-versa.

Corner frequency: -3dB point 150Hz
Slope: -6dB/Octave
External Sidechain input impedance: 10k Ohms from each leg to ground.
Normal Input is wired one to one (pass-through).