Sorry if it came across rude but I thought it was plain as day that it was a "bass boost knob". I have never seen a remote gain knob in any car thus far in my life since the adjustment is on the amp thus validating your point of useless which I would agree on, however I always see the little bass boost knob in EVERY persons car that has a sub so I figured you guys would know.
gckless: A standard phone cord WILL fit and that is what I tried and got no response from it, which triggered this thread. It is NOT big enough for a cat5 (ethernet cable).
Will post a pic ASAP.
Yeah that's what I thought. It's a RJ11 connector. Refer to my post about the pinout. You got no response because of two things: a standard phone line only uses 2 pair while these bass knobs use 3 pair, and the pinout is different on even those 2 pair that the phone line uses. Try those two options I gave you, one will probably work. Although I can't guarantee it the exact pinout, like I said I only looked at two.