Greengecko

Hey guys,
I want to attach a bass processor to my sub output from the stock head unit *before* the amp, cause I need a low-level signal for this device. I'm going to splice some RCA plugs into the wire using T-taps, but I'm not sure about the polarity of the wiring. I know that the center post is positive and the outer flange is negative, but what does that correspond to in the wire when you open it? Thanks.

Desert_TL

When you cut the RCA wire, chances are good that the wire will consist of an outer shielding with an inner core. That is, there will be one conductor that is surrounded with insulation. Then that insulation will be surrounded with a wire shield, then the whole thing has another layer of insulation. The inner conductor is the tip (positive).

If you're still not sure, you can use an ohm meter as a continuity tester (i.e. touch one probe to the tip of the cable and the other probe to one of the exposed wires. 0 ohms means you're touching the same conductor). Cheap ohm meters can be had for less than 10 bucks, but if you're doing lots of audio wiring, a good $30-$40 multimeter from radio shack is a good investment that takes lot of headache out of electrical work.

Greengecko

Thanks, Desert_TL, I had just guessed that the tip of the plug would be the positive, since the positive tends to always be more shielded than the negative or ground in these situations.

I was splicing into the preouts in my 2004 TL to correct a problem I was having with terrible bass quality. I turns out the polarity in these diagrams I got from Crutchfield must be backwards, because as soon as I reversed wires at the source, everything cleared up. The same was true of the high-level outputs of the stock amp.