QU 16 - ST3 input - how do I mono this

I manage a Qu 16 digital mixer. Our mixing strategy is mono, so no panning on any mono inputs. Therefore same signal goes to main outputs Left and Right.

When I send a stereo input into the 1/8th inch ST3 input, such as the output from a mobile phone, or laptop, I’d like this to be mono, and I have not figure out a way to achieve this. Maybe it exists and I have not read enough of the manual.

The approach I had in mind which I know will work, would be to convert this to two mono inputs, via a suitable cable, pair these two mono inputs - i.e link them together, and adjust the panning, to make it mono. this I know will work, but that’s using up two channels.

It would really be nice if I could use ST3 which is the perfect input for my needs, and just mono it.

Thanks in advance. Highly appreciated.

There is no real provision to do the above from within the desk, I don’t think so anyway.

With a stage box you can send L+R to an output. Without a stage box you would need to make or buy a stereo to mono outboard device.

If you have a system processor DSP look at doing the mono summing in the DSP.
If your not already using the ALT OUT you can select L+R mono summing as an ALT OUT option.
Or…look up “Rane why not to Y” they a the schematic for a passive summing circuit using resistors, it works
well I’ve made a few, you can fit the parts into an XLR connector.

Thanks everyone, your responses are highly appreciated.