Upstate Auto Detailed: Frank's Trailblazer SS

Actually, since you offered, if you know your stuff about car audio then i might need your help with this one. I’ve done a bunch of car system setups before including two of my own but i’ve always changed my headunit out for an aftermarket one. With my TBSS i want to keep the factory headunit but add a sub and an amp. Reason being is because if i replace the headunit in this truck i have to buy like 3 seperate modules to bypass some stuff and keep some other stuff functioning properly. To me its too much a headheache and too much money so i purchased this bass restoration device/Line out converter called an MTX re-q5. Not sure if you have ever seen or installed one but im all tripped up over how to install it. All i know is that i have to tap into the stock speakers wires at the factory amp or behind the deck in order to get a signal to my amp via my rca cables. But im not sure how. So if you could help me out on this that would be sweet because im honestly confused as hell. PM if you think you can help and ill shoot you my cell # so we can meet up.