QuestionI have... 1994 Eddie Baurer 4x4 with audiophile sound system... seperate main amp (front and rear) and seperate subwoofer amp.
I replaced the HU with a Pioneer DEH P4100UB (3 pair of pre-amp outs [front/rear/sub])
for the front and rear I used the speaker output wires bypassing the main amp with the Crutchfield bypass harness. This works fine. But since the subwoofer gets it's signal form the main amp... no sub output.
So I cut an RCA cable in half to connect to the HU Sub preamp outputs. Twisted the grounds together. Connected these to a 3 wire cable and ran that to the back to test...
Now here is where I differ from everyone else so far...
The only connection from the main amp to the sub amp is a cable from the bottom of the main amp to a connector into the sub amp. This cable had 3 leads one black, one clear and one bare twisted wire... these are surrounded by a foil sheild.. not used. So I would have to assume this supplied the sub amp with a preamp signal. At the top of the subamp are the 2 power leads red and yellow. Verified that they are 12 volt always on. They enter the top via a grommet. In the center top of the sub amp is a large grey connector with only 2 wires both black... again I assume these are the output from the subamp feeding the subwoofer speaker.
So trying various connections from the 3 wires from the sub preamp to the 3 wires going into the sub amp have yielded no sound from the subwoofer. (I have verified that the HU sub out is turned on)
Although I haven't actually tested this I am fairly confident that the 2 black wires coming from the top of the sub amp are feeding the subwoofer. I do know that the heavy guage red and yellow wires are 12v constant power.
So... anyone have anything to help me figure this out?
bob
AnswerHi Bob,
Unfortunately, I wasn't able to come up with a wiring schematic for your particular vehicle's audio system. I think I'd be following pretty much the same steps that you are: the foil-wrapped harness running from the 4-channel amp to the sub amp must carry the audio signal, and it should be possible to tap into it using the new head unit's RCA output. The bare wire won't be a signal wire; it's included as a "drain" wire to help prevent induced noise. That leaves one of the other two wires as the signal wire, and the remaining wire is probably the signal ground. However, it's possible that one of the wires carries an amp "turn-on" voltage. If the yellow and red wires are constant, and not key-switched, power wires, then there should be a control wire that switches the amplifier on and off. This is likely to run from the 4-channel amp to the sub amp.
Without a schematic, you'll have to fall back on a digital multimeter to test the wire functions. To do this, you'd probably need to re-connect the OEM head unit. See if you can find a wire that runs between the amplifiers, and carries a voltage whenever the head unit is switched on (or, at least, whenever the key is on). If you can find a turn-on wire, you should be able to apply voltage to it to activate the sub amp. You may also be able to identify the correct signal wire, by testing for AC voltage that varies with the system volume level.
Hope this helps!
Brian
