Tobias is correct. The FX send output is a mono signal that bypasses the internal FX engine. It is a mono signal regardless if the signal comes from a mono channel or a stereo channel. On a stereo channel, the FX tap is a sum of the LR signals post fader.

The Mixer outputs the Main Mix from the Main Mix LR outs and the Tape Out. These signals are exact duplicates, including the levels of the gain and fader settings. It can also send the Main Mix to the CR outs and the headphones out or you can switch so the CR and headphones output the Tape In signal. This is switch selectable.

The FX outputs a mono mix determined by the FX knobs on each channel. This is a separate mix from the Main Mix in levels. The FX output is affected by each channels gain level and fader level. It is also affected by the EQ and Low Cut settings.

This mixer will definitely work with IEM or stage monitors or as an output to a recording device. The OP just has to decide if he wants to 'hear' the Main Mix with or without effects or an FX mix without effects. He MAY be able to return the FX send to a L (mono) input of a spare stereo channel to use the internal FX engine but it's doubtful since he will be adding the FX send from this channel to the FX send output and likely will create feedback. He will have to test it to determine if it works. I doubt it.
If he wants to hear the FX's in his monitor mix, he will need to use the Main Mix.

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