when used as 4in-1out, parang mixer na rin...without the controls. and no power supplies needed. if keyboard player ka tulad ko, and you have 2 keybs+2 modules, and your amp is gawa sa .... hmmm ... pwede yan.. kahit sa karaoke/videoke ok yan. apat na mics( optional if you want to make 4 I/O ).
Pagawa mo na lang sa ELX Expert if you don't know how to DIY. good luck.
Always sound test at low volume levels first.
experts, please make some corrections if possible, then post your modifications... ...but its working fine on my system.