How do I run 6 rca’s from my 5 channel car amp to one aux cord?
That is the worst mess I've ever heard of that you want to do. If you're just stringing a bunch of speakers together with intention to play *into* your phone with 5 or 6 RCA cables, there is no way to do that. Wake up and stop having that nightmare.
A 3.5mm to two RCA cable to get stereo audio from the phone. (Or a bluetooth receiver board). Then splitter cables to connect all "left" inputs to one stereo channel and all "right" inputs to the other... eg. a 3.5mm to two phono sockets / rca jacks https://www.ebay.co.uk/itm/3-5mm-Stereo-Jack-to-2-Phono-RCA-Sockets-Adapter-Cable/190480937107?epid=1205086408&hash=item2c598c7093:g:g~YAAOSw2xlcL3DD:rk:3:pf:1&frcectupt=true and splitters https://www.ebay.co.uk/sch/i.html?_odkw=3+5+mm+to+two+phono&_blrs=spell_check&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR7.TRC1.A0.H0.Xphono+splitter+cable.TRS0&_nkw=phono+splitter+cable&_sacat=0 And optionally add a bluetooth receiver to avoid plugging in to the phone itself: https://www.ebay.co.uk/itm/Bluetooth-HD-Audio-Receiver-Wireless-Music-3-5mm-AUX-4-Speakers-Car-Stereo-Hi-Fi/191834243145