DIY volume potentiometer instead of crossfader for Reloop Spin

[rsq]

Hi,

I have a Reloop Spin portable turntable, which got two slots for crossfaders (for left and right handed).
I just got a Jesse Dean fader which works great, and still have an available slot for a second one, which I do not use.

As there is no volume control for the vinyl (only a knob for the external input), which is not practical because the vinyl is sometimes much louder than the input at max level, I thought it would be a great mod to add a simple potentiometer to the second slot to reduce the volume of the channel of the vinyl, without having to unsolder anything, using the standard crossfader connector.

I know a little about electronics but nothing about crossfaders... As far as I know each slot got 2 connectors, one analog and one digital (I think the white is the analog one).
There are 4 pins on the connector: vcc-, xctrl_a, xctrl_b and vcc+.

I thought it would be very simple but well, I can not manage to wire a simple potentiometer to reduce the volume of a channel... I made some test but it acts really strange and I'm a bit afraid of damaging the electronics by doing a short-circuit or something...

Does anyone already did something similar or knows more about how crossfaders wiring works ?

Thanks ! I can post photos if needed

[electroshock]

What does the volume knob do?

[rsq]

What does the volume knob do?

There is a global output volume knob, and another one for the aux input/bluetooth. But nothing for the volume of the record.