This forum has been a great informational resource for me, lets hope it does not end here .

I have learned that the factory amp channel that powers the rear 6x9" has a bass boost at 40hz. This explains why the sound coming from my sub is extremeny strong at only some frequencies, and very weak in others.

What I want to do now is take the pre-amp signal from behind the dash, and run it back to my amp via RCA's.

Please tell me that someone knows how to do this, and can let me know what the best way is ?

Also - I think Altersys has a wiring diagram if our sound system - does anyone else have it ? I could use it as well.

 

Let me know if you find anything i have noticed that myself with mine.

 

I can still fax you the diagram if you want it, but here's the color codes (these wires are located on a harness that plugs into the factory amp underneath the head unit and behind the NOT AN ASHTRAY pocket

on the SMALLER connector:
line level signals and shieldings are as follows:
Driver: RED/BLU (+) / YEL (-) [B1, B8]
Shield: BRN [B5]
Frt Pass: BLU (+) / RED (-) [B4, B11]
Shield: BRN/YEL [B2]
Left Rear: BLU (+) / PNK (-) [B3, B10]
Shield: GRY/BLU [B9]
Right Rear: LT GRN (+) / PUR (-) [B6, B13]
Shield: GRY [B12]

Remote lead: B7 (YEL/GRN)

The cavity number (Bx) represent the connector viewed FROM THE HARNESS SIDE (not connector side) with B1 being the epper left cavity and B14 beind the lower right one.

Use the shield wires by soldering them to the shield on your RCA cables (you will need to take apart the "upstream" half of your RCA cables to get access to the shielding. Doing this is important as it shorts the factory shielding to the aftermarket shielding. Directional RCA's ground the shield at the AMPLIFIER and float it at the source. This way, any noise picked up by all leads on the RCA length will be referenced to ground at the amplifier and will not get amplified. If you skip this step, you might introduce noise into the system. It is important to get directional RCAs for this to work (or anything with a shield that is grounded at at least one end).

Now, I do not yet know the max unclipped voltage of the factory head unit preamp signal (if you discover it, I would be obliged if you reported it here), so you might benefit from a line driver. I want to find out what the voltage is before buying one, because if it's high enough, it won't be necessary.

BTW, I don't take responsiblity for any errors or omissions in this post... cut-n-splice at your own risk! if anyone finds an error in the text diagram I just copied, please let me know so I can edit this post.

 

Thanks Alt - I got the diagram from another thread, it was posted on someone's webpage.

However I dont think I will need to do any re-wiring. I am an idiot, and as such had the LP filter engaged from my amp as well as a +12 db punch bass. That combined with the already enhanced bass response of the rear 6x9s at 50 hz was causing the sound changed I was talking about.

I was sure I turned that off when I was wiring, maybe the stereo gremlins turned it back on. Anyway it sounds much improved now, and it will be even further when my Alpines arrive.

 

Best of luck...