Hi guys i need some help, i have heard something about 4 cable connection but really i dont know how it works.

My problem is i want to connect the M13 + Korg Sdd2000+Korg A3 on the Vox AC30

for what i see on the rear panel of each effect i have:

SDD has midi but not seems have a real send/return unit

A3 has midi but not seems have a real send/return unit

M13 have both and the Vox have the rear inputs for send and return system

I wish i connect all the system in order to control in a unique way (better using the midi system of M13) the other 2 effects and create a chain that sounds good, loosing less sound possible.

Can someone help me?

thanks