Topic: External send effect with Mainstage and TotalMix

I'm fairly inexperienced with mixers and would like to set up an external send effects unit (G-Major) connected my FireFace 400 (FireWire model) via SPDIF. If I understood correctly, a send effect allows me to dial in the amount to process using the Send knob on the Mainstage mixer. My inputs are as follows:

Guitar (preamp and CAB simulator) connected to the channel called "AN6 PSA CAB" in the image.
I would like to route "AN6 PSA CAB" to SPDIF output and receive via SPDIF. I'm stuck on what setting I should use.

I have tried going to the SPDIF submix and increasing the level of "AN6 PSA CAB" to 0dB to send it on SPDIF output, but that takes away control from Mainstage's Send knob it seems, and the effect is always audible, regardless of the Send knob in Mainstage.
I'm monitoring on 7/8 headphones.

Also, the MIDI ports tend to disappear from TotalMix and Mainstage... irritating. Kernel driver 3.39, Unit v1.70. … =4096x4096

2 (edited by eriksan 2020-03-01 22:39:08)

Re: External send effect with Mainstage and TotalMix

The solution was to enable output on the Software Playback SPDIF, and select channel 9-10 as both input and output in Mainstage's I/O plugin. However, the disappearing MIDI outputs are still a major concern! I'm on MacOS Catalina 10.15.3.