03 Trailblazer factory head unit question

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=15127
Printed Date: July 26, 2025 at 11:10 PM

Topic: 03 Trailblazer factory head unit question

Posted By: Lboy
Subject: 03 Trailblazer factory head unit question
Date Posted: June 18, 2003 at 5:48 PM

I was wondering if anyone can tell me a little bit about the factory head unit/non Bose system on an 03 Trailblazer.
I'll be buying one shortly and the stereo install thoughts are already running through my head.

I plan on adding a rather simple system comprised of 4 new speakers in the factory front and rear openings powered by a 4channel amp as well as a single sub powered by another amp.

For the sake of simplicity,I was thinking of keeping the factory head unit and running its signal to my amps. It seems that integrating into Onstar,and keeping steering wheel audio controls is going to be a pain,so would keeping the factory head minimize the hassle? Or would keeping the head unit just be a waste of time?

How can I run from the head to the amps? Will I need to convert the high level outputs to a set of RCA's with a line out converter? If I do,how clean will the signal be going to the amps?

If I decide to go with an LS model that does not have OnStar or steering wheel controls,would it be smarter and simpler to just go with a new head unit?

Thanks for any information you can give me. I'm just trying to get an idea of how the audio setup is in the truck in order to realize what my options are.

Replies:

Posted By: SoundImage
Date Posted: June 18, 2003 at 7:08 PM

if you run a line level the signal will be clean it just won't have a lot of voltage. if you replace the head unit and it has door chime you need to buy the radio relocation wire harness. it's a little bit of work but worth replacing the stock headunit for a serious system

Posted By: ViperATC5
Date Posted: June 18, 2003 at 7:25 PM

Actually did the same setup in an 03 Tahoe last week-

Keep the factory head unit and use a LOC to get a low level signal. Cut output wires coming out of the factory amp behind the glove box and get your hi level signal for the LOC on the side of the harness that will still be plugged into the amp (Important to leave it plugged in so that you can get an amplified signal for your LOC), and then run your 4 sets of speaker wire from your aftermarket 4 ch amp to the factory amp and connect the speaker wire to the other side of the wires that you cut, as they will go to all the speaker locations. We did a rockford 500x and a 601s, so we used a 4 Ch LOC with adjustable gains (PSI2 - available at Best Buy for $40) to get both the front and rear signals to maintain fade and balance, and then we used the pass through on the 501x to run signal to the 601. Setting it up this way allows everything that would normally be run through the factory system to simply be run through another set of amplifiers.

This setup doesnt give you as much control over your audio system as an aftermarket deck, but doing it this way will save you the hassle of using the relocation harness and onstar integration kits. The Tahoe sounded awesome after a little bit of tuning.

Posted By: Lboy
Date Posted: June 19, 2003 at 6:26 AM

Cool,thanks for the info.

At this point I think I'm going to start out by keeping the factory head unit and running a LOC to get signal to the amps. I also like the fact that the system will appear to be stock,with the only thing showing being the subwoofer which will be covered by the retractable cargo area cover anyway.

Woulda anyone recommend a Line Driver between the LOC and my amps in order to step up the signal voltage? If anyone is wondering,I'll be powering the system with a JL Audio 500/1 for the sub and 300/4 for the F&R.

Thanks again for the help.