[jrglenni]

So I've finally purchased a Sosche FDMUS05 12" Sub and enclosure to place in my trunk. Now I've been trolling several forums in search of an ideal solution of how to connect the amp to the head unit. At first I was going to get a line-level converter and take the rear speaker inputs and get a set of RCA's out of them, but as I read several posts, I started to think that there was a better way.

Take a look at the wiring diagram below:
http://www.allfordmustangs.com/forum...achmentid=5967

And take a look at these wiring harnesses from Crutchfield:
(See below)

Going from the diagrams and the product descriptions, the smaller of the two wiring harnesses from Crutchfield definitely matches the J4 plug of the stock head unit. On that harness, there is a set of RCA cables coming out. It seems that these RCA's would plug into an after market head unit and the signals would be carried down the existing wiring to the factory Shaker 1000 amp/sub, which leads me to believe that there is a low-level output coming from the back of the Shaker head units.

My question to anyone that knows much about this stuff is, how would I take a RCA-to-twined cable and wire it into the J4 plug to make a proper RCA out to plug into the amp? I have a couple guesses but I'm not entirely sure.


So using 2 of these (I'll call them RCA-A and RCA-B):
(see below)

I'm GUESSING that I would wire it like so...
RCA-A+ --> J4P1, Aux Aud 1+
RCA-A- --> J4P3, Aux Aud Shield
RCA-B+ --> J4P2, Aux Aud 1-
RCA-B- --> J4P3, Aux Aud Shield


Can anyone confirm that or let me know if that's completely wrong? I


In any event, I plan on positing my findings here since this seems to be a question that a ton of people have and the threads that address it die out before a solution is presented.

On a side note, I've also found some posts that suggest the remote power on and low level outputs on the shaker 500 output extend to the trunk somewhere, even though there is no sub/amp. When I start to tear things apart I will take a look at the J4 connector and see if anything is plugged into it, and if there is, try and follow it back to see where it goes.




I apologize for any confusion, somehow my links to Crutchfield and maybe Radio Shack seemed to break the post/thread.

Anyway, long story short, the wiring harness on crutchfield can be found if you do a search for "Ford Wire Harness"

The cables I was referring to on Radio Shack are part# 42-2371

[GT speeder13]

i did the line level converter, and it worked just fine for me. think about it, its only a bass signal that the sub is going to pickup, so it doesn't have to be a direct RCA connection, because quality is something that you cannot tell from bass notes (if there is a difference, its so small that you cannot tell).

I would recommend an RCA hookup if you planned on powering your rear and door speakers with an amp though!

[jrglenni]

It definitely works that way, but if you consider the fact that your HU does a bit of signal processing then puts out a signal that is predetermined to match your rear speakers, then you take that same signal and lower it so that your subs pick it up, its not a bass signal the way its meant to sound.

Again, it works, but if your HU has an output intended to be used with a sub/amp, why not use it. It would be much easier if I had a line-level converter that didn't actually do any converting, but it shouldn't be too difficult to figure out what wires need to be spliced to where in order to get things accomplished. Theres always a bit of trial and error if no one knows for sure.

[jrglenni]

Ok, I spoke to a friend that knows a lot more about the finer details than I do, and apparently I was mistaken about what exactly the line level converter does. For those who don't know (and how it was explained to me) the line level converter takes a high level signal (power wise, not frequency) and drops it down to a much lower power. As long as you have the full frequency range going into the converter, you will have the full range being output. From there, crossovers, either in your amp or standalone, can pull out the signal that you want.

Going by that, I will probably just run the line-level converter off of the rear speaker connections and then run the +12v turn on from the AUX AUD Enable connection on the J4 connection.

[helix139]

Get a SoundGate LOCB.2 active line level converter. You can intercept the line out signal from the head unit to the factory amps(cleanest signal), and the voltage on the pre-amp outputs will be higher. DO NOT use a standard non-active line level converter on the line-out signal to the amp as you could damage your head unit or speakers

[jrglenni]

Well I just went with a Scosche Line Level converter. I went to run the turn on lead off of the back of the stereo, but that was a pain to remove and I couldn't find a good spot to tap into the wire, so I tapped into the stereo power fuse (#20) on the passenger side fuse box. Unfortunately, I think my amp is dead, so I didn't get a chance to hear it. I have some more testing to do but my amp is damn near 10 years old now and its seen its share of abuse so I'm not surprised.

[jrglenni]

Another follow up, the #20 Stereo Run fuse that I tapped in to wasn't what i thought it was. It seems to be the fuse for the remote start if its installed through the stereo. Anyway, I move the turn on lead from that fuse to fuse #12 and now I'm getting a proper signal to turn the amp on when my key is turned.

Also, my amp wasn't dead, either the Scosche converter was or I didn't have it set correctly. Either way, I returned it and bought a different one, and it works now so I'm happy.

For the ground, there is a threaded hole under the carpet near the trunk on the passenger side, its covered with a piece of clear plastic. I removed the plastic and sanded down the paint around it then screwed a bolt into it to hold my ground cable, worked nicely.

[crashed1st2]

i got a scosche in line converter (fai-3a) and wanted to add subs/amp by splicing into the rear speakers in the trunk. is this possible/has anyone done this and can you help me with some tips

[jrglenni]

Take a look at http://www.mtx.com/caraudio/products...ms/FMUST05.pdf

That has a guide for which rear spiker wires to tap in to.

For the +12v turn on from the amp, use the #12 fuse in the passenger kick panel fuse box. If you can find some wire taps to neatly tap into the fuse, then go for it. I couldn't find mini ATC fuse taps so I just stripped a small portion of the wire and inserted it into one side of the fuse panel and then slid the fuse in over top of it.

For the ground, I used the threaded hole in the trunk that I described in my previous post to attach the cable to.