Looking at the block diagram (P9 in the manual), The Fx bus signal routes to the internal Fx and the Fx send output. The internal Fx input and the Fx send are the same signal at the same levels. The Internal Fx routes to the Main Outs only.

For returning the Fx signal back into the mixer:

Tape In (a line level signal) can be routed to the Main Outs directly or
to the CR/Phones Output. Tape In has no routing to the Internal Fx.

Mono Channels Can simultaneously route to the LR Main Outs and the Fx Bus.

Stereo Channels can simultaneously route to the LR Main Outs and the Fx Bus.

The Internal Fx unit's on/off status and level is determined per channel by the position of a channels Fx knob and the Fx to Main knob.

So, any signal or combination of signals fed to to the Fx bus from any Channel, out the Fx send and routed by any of the Channel input types (Mono, Stereo), will route the Fx Send signal of that Channel input back into the Fx bus. I think that resultant summed Fx signal could cause a feedback loop Because the Fx send knob of that Channel will have to be turned up to feed a signal to the Fx Internal Fx unit.

Last edited by Charlie Fogle; 09/17/18 01:11 AM.
BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.