Just stumbled across this in the QC manual. The QC has hum canceling technology built in. It looks similar to Fractal’s Humbuster feature, if you are familiar with Fractal Audio’s devices. You can apparently connect a TRS to TS cable from Sends 1 or 2 and reduce hum.
This can come in really handy. You can order a Humbuster cable directly from Fractal or if you search the Fractal FM9 manual for “Humbuster”, you can see how to make your own. They may be available from other sources as well.
Not sure why they did not include this technology on Outputs 3 & 4. That would have made more sense to me. Maybe they were particularly targeting 4CM usage. However, very cool it exists at all. Potentially very useful if you are connecting to an amp or other device that is generating hum, or perhaps are in a venue that is. You would have to employ Send 1 or 2 in your connections.
Note: I am assuming the wiring for Neural’s TRS to TS cable is the same as Fractal’s but that is unconfirmed. Neural should add a wiring diagram for their hum reduction cable to the next manual revision.
From the manual (see page 117 of the Quad Cortex 2.10 User Manual for diagram):
"This feature works by connecting Quad Cortex to external devices
by using a modified instrument cable (TRS and TS ends). Connect
the TRS tip to the Quad Cortex and the TS tip to the external device.
These cables do not eliminate noise, but they can significantly
reduce hum caused by ground loops.
Both Sends 1 and 2 support this feature. "