Line output converter help
So I installed a line-out converter to my REC nav unit until I sell it so I can hook up my amp and sub. Followed the instructions and used a quick connect from the rear right and left speakers to l.o.c. Ran the remote from the acc. on the deck.. Amp turns on and sub works. However the sub is at full volume even when the volume is on 1. When i turn up the volume the sub doesn't get any louder. I got a metra converter that has a ground wire and even tried grounding it and still the same thing. Did I miss something?