XMSJSIY Universal RCA Level Controller Car Audio Amplifier RCA Audio Adjuster Bass Boost Volume Control Knob and Cable for Car Motorcycle Speakers Home Theater

My car stereo doesn't have sub control so I used this in between the amp and it works perfect! Great adjustability, easy to install, great bass and volume control. Excellent value for the money!

$15 and decent quality. Don't forget to have some rca cables kicking around to run from the head unit to this, I just used some old colour cables. Don't forget to adjust the gain on your amp for the max level on the knob.XMSJSIY Universal RCA Level Controller

I bought a couple of these, because the signal levels out of my CD and CR-R drives are quite a bit stronger than the other inputs on my stereo system: up until I cut these into those lines, I would have to turn the volume down quite a bit, when switching to CD from FM, phono, or tape. These solved the problem quickly and cheaply, with no need for an external power source.Note that the input and output pigtails are clearly marked, and (assuming this is wired as a voltage divider) not interchangeable.

As described. Easy install. Works well. So nice to be able to control subwoofer from the comfort of the drivers seat as required

Very simple potentiometer with RCA jacks. Works 100%, but not the greatest build quality. Great if you're on a budget.