Hey! SOLVED!
So, here's the final setting that works for me!
You'll need:
a Dunlop Mini Volume (X) MIni DVP4
a normal 1/4 TS cable, which is actually 6.3 jack cable patch.
Follow the steps as downtowndalebrown suggested
Step 1 - Open up the back of the Volume Pedal and make sure the dip switches are set to Exp and Ring
Step 2 - In Global Settings on the HX Stomp, set Ring Polarity to Inverted.
UPDATED step
Step 3 - Plug the patch cable into the 1/2 EXP input jack of HX Stomp - Plug the other side of the cable in the AUX input jack of the DVP4
CONSIDERATIONS:
It still doesn't work if I insert the TS cable in the OUTPUT input jack of the DVP4
I hope it will help