This diagram explains how to wire the included TRS jack in the kit to function as an INSERT jack.
Do not forget to short the two terminals on the jacks. This connects the SND connection to the RTN connection completing the circuit if there is no TRS jack inserted.
If you insert a TRS jack, then signal flows from the SND (TIP) to the outboard gear, then back to the RTN (RING), then back to the SC-1 preamp.
RTN-GND is the "ground" connection.
If you're using the INSERT jacks, don't forget to remove JP2 shorting jumper.
If you’re using the INSERT jacks, please keep a couple of things in mind.
1. The Send signal is “unbalanced.” Therefore, it is recommended that this cable be kept as short as possible.
2. The Return signal is also “unbalanced.” Therefore, it is recommended that this cable be kept as short as possible.
The signal from the preamp will now be traveling a farther distance if you’re using INSERT jacks compared to the shorter distance if JP2 is shorting the SND and RTN pads. Not only will the signal be traveling a farther distance, it will also be an “unbalanced” configuration… that means, the possibility that noise get in the system/cables/wires is big, and this noise will be returned back to the preamp for further amplification by the balanced output driver. (See block diagram of SC-1).
If you don’t need the INSERT feature, you can safely just leave the TRS jack out and just use only the JP2 jumper.