Stock Alpine add on sub solution.

Hello fellow LS'ers. I have a question about adding a sub the stock Alpine head unit. I already did a search and learned a lot about how I can't do it. Is it possible to intercept the signal coming from my CD changer and use that as a line level sub input? The theory is to get to the signal before all the head unit processing takes place. Opinions?
What were talking about:
2000 LS w/Alpine HU + 6 disk changer in the glovebox.


P.S. If you tell me to go aftermarket I won't listen, I'm hard headed like that...PB

If you grab the signal from the CD changer, your sub will only work when listening to disks in the changer, not on radio, cassette, etc. Also, you'd have no control over volume or tonal quality from the deck controls (bass and treble).

You could pull the radio apart and bring out the preamp stage for use with the aftermarket amp.

-Rod

If you grab the signal from the CD changer, your sub will only work when listening to disks in the changer, not on radio, cassette, etc. Also, you'd have no control over volume or tonal quality from the deck controls (bass and treble).

You could pull the radio apart and bring out the preamp stage for use with the aftermarket amp.

-Rod
Hey Rod. Sorry, I've been away.
I kinda figured my sub would only work with CD's. I don't have too many cassette tapes anymore and I hate the radio. As far as controlling the volume, my amp has a remote bass control knob.
Pulling the stock HU apart and getting to the preamp stage is a good idea though. Is there a link or search keyword to anyone that has done it?
Thanks for being the one and only to reply...PB

I'm not aware that anyone's actually done this for your model. Although if you are confident with tools (including a soldering iron) and have access to an oscilloscope, you should be able to determine which pins at the brick amplifier ICs in the head unit are the signal, or the amps might have COTs amps in them in which case you could pull down the datasheet.

I'll also take a look at the wiring diagram, maybe there is an unused connector on the back of the head unit that already has the line level output to an optional amp that your car doesn't have. My recall though is that Ford typically uses a differential low-level signal though so you would still need to convert the signal.

Since you are just looking to add a sub to the system, you may want to use just a line level converter (voltage divider) from a pair of the speakers to provide the stereo signal to the aftermarket amp. The sound quality would be good enough for the sub.

In your original post you mention the theory is to get the signal before the head unit processes it. Why is that? If it's to be able to crank up the bass without worrying about distortion, then you can do that with the gain of the amp or by adding non-polarized capacitors (aka "Bass Blockers") in series with the door speakers. I think the center image speakers are already high pass filtered.

-Rod

It would appear that unless your LS is the sport version, you should already have subwoofers in the rear deck. Those subs are powered by a subwoofer amplifier mounted on the deck as well. The connector feeding this amp, C466a, has a mono signal going to it. The wire in pin 7 is the subwoofer audio signal positive (White wire with red tracer) and the wire in pin 8 is the subwoofer audio signal negative (Gray wire with red tracer). There's a third signal wire in pin 9 referred to as "Subwoofer, signal, Drain wire" which I'm guessing may be the reference level and the wires in pins 7 and 8 are bridged and labeled with respect to the drain wire.

I don't find any documentation showing what level these lines are at, so you really should measure them with an oscilloscope to determine if they are safe to run in to an aftermarket amp as low level. If you don't have access to a scope, then a test CD with a constant tone and a true-RMS multimeter would suffice.

-Rod

Hey thanks alot man!