Hello,

I am in the process of upgrading the stock stereo in my (non-nav) 1999 3.2 TL.The overall plan is to:

-keep the stock head unit
-replace the door speakers
-bypass the outboard EQ unit
-run a Blitzsafe line-in to the head unit for a Harman-Kardon Drive+Play iPod adapter
-power the 4 door speakers with an external, 4-channel power amp, mounted in the trunk
-(possibly) disconnect or bypass the stock subwoofer amp and speaker
-(possibly, at a later date) add a second amp, subwoofer, and enclosure in the trunk

So far, I have replaced the 4 stock door speakers (Infinity 6.5" 3-ways in the front, and 5.25" Sony 2-ways in the rear). I have also installed my Harman-Kardon Drive+Play, using a Blitzsafe HON/AUX DMX V.1 into the CD changer input on the back of the head unit. I managed to plug the Blitz adapter in without having to actually remove the head unit, so that was a bonus. That was enough work for one day, and so far, everything has gone as exactly planned.

At this point, I'd like to insert a huge thank-you to all the contributors to these forums - I compiled quite a lot of useful information before beginning, from a basic understanding of how the entire audio system in my TL is configured, to detailed instructions for removing the door panels, centre console, and head unit. Special thanks go out to this guy (sorry, I can't find your name anywhere on your posts), who's efforts to document his installation and provide the schematics for the car wiring were truly invaluable. I would probably never have attempted any of these upgrades without having this info, and if I did, I'm sure it would have been a nightmare of trial and error, and broken components, trim, and clips.

The next step is to actually remove the head unit, bypass the outboard EQ module, and to connect the outboard power amp to drive the 4 door speakers. I have obtained wiring harnesses to mate with both the head unit and the car harness, so I can pre-wire the harness to the amp, and do as little cutting to the existing car wiring as possible.

My question is regarding the signals from the head to the amp. I have a JBL GTO 75.4 II amp, which is a 4 channel amp, and accepts line level or speaker level inputs. If I want to use the speaker level outputs from the stock head unit to the amp, I'll need to run 8 wires back to the amp from the head, along with a remote power wire, and then run 8 more wires back from the amp to the head, where I'll tie into the existing car harness, and out to the 4 speakers. The other alternative is to tie into the line-level signal from the head unit, which would normally go to the outboard EQ, but instead, I'd bypass the EQ altogether, and run a single shielded, 3 conductor cable from the pre-eq output of the head, back to the amp, and then split it into two pairs of left and right RCA connectors, into the front and rear inputs on the amp.

So, the question is, which is the better method? Using speaker level inputs to the amp has the advantage of retaining fader control from the head unit, whereas using the line level output means less overall wiring, but loss of fader control. Areas where I'm unsure:

-will the bass and treble controls in the HU still work if I tap off the line level outputs, or are they in the HU circuit after the outboard EQ?

-which method is less likely to introduce alternator whine noise - unshielded speaker wires (being careful to not run them near the amp power wire), or a shielded cable from the line level output of the HU?

I've searched the forums, but not actually found answers or discussions on these particular questions.

Thanks in advance for any help, and thanks again to all who've taken the time to contribute their experiences.

 

Preamp level is best, speaker level is more likely to have noise, tone controls will still work.

Don't worry about the shielding, just use twisted pair from your amp to your new amp. Remember that that's a balanced output, if the JBL doesn't take balanced in, you may need a Soundgate LOCB.2 or a Peripheral SVEN.

 

elduderino,

Thanks for the info; I'm a bit confused though; my understanding is that a balanced output has a +, -, and common signal for each audio channel, where the + and - are 180 degrees out of phase; my understanding of the TL's audio system is that the outputs from the head unit to the outboard eq are: left, right, summed (mono signal for subwoofer amp), and common. The summed output is run through a low pass filter and sent on to the subwoofer amp, and the left and right signals are eq'ed to compensate for the crappy stock speakers, and then returned to the head unit, where they are amplified internally.

I guess the main question is (based on your feedback), is the left/right/common signal coming from the head unit (before the eq) sufficient to drive the RCA inputs of a power amp (i.e. line level), or are they "low level" signals, which still need to be run through some sort of converter (such as a locb.2) to raise them to line level? I'm now starting to suspect the latter...

 

I have not done a TL as you describe. If it has common-grounded outputs, then no device should be needed and you should be able to go straight in.

The only way to test if it's "enough" is to put in a sine wave test CD and measure the output with a voltmeter. OR, just go ahead and do it - if it's not "enough", get a line driver.

Caveats:

1) Since it's not balanced, noise from EMI induction is possible. Use twisted pair.

2) You still might have a ground loop. I'd put female RCA ends at the point of wire tap, run m-to-m RCAs to the amp, and then you can readily add a GLI if need be.

 

Just for the sake of argument and another opinion (not saying elduderino is wrong), David Navone (longtime, respected engineer) has written often, including doing electrical studies, on the advantages of using speaker level outputs. He believes it so much that he has developed his own LOC's (http://www.autosound2000.com/).

Also, you can post to the forum that he moderates to get more info. He emailed me several articles that he, and others, wrote on the topic.
(http://www.carsound.com/UBB/ultimate...?ubb=forum;f=2)

 

Ah, Navone.

He does love to talk and lecture. Listening, he's not so good at. Try talking to him sometime. And based on the feedback I've gotten from many in the industry, I will quibble with "respected" a bit. How about "established"? He definitely is a legend in his own mind and a good self-promoter.

Look, his LOCs work well in some applications. Unfortunately, the transformers are susceptible to picking up EMI noise in cars. He also makes LOCs that work with balanced signals, so I can't see giving him credit for what you state - he wants to sell widgets, either kind. He also totally gives a pass to the following:

1) If you go through the amp, the odds of you having signal processing of some kind go way up. Most cars, you can't remove the EQ, like in this car. But if you follow Navone's advice, and you don't have an audio analyzer (most don't have one), how would you know?

2) Your signal will always be more distorted by going through one more device and one more splice - not to MENTION the poor audio characterstics of most IC amplifiers. Why purposefully insert into the signal path a part that was chosen by an automaker contractor to be as cheap as possible?

3) If you go after the amp with a system with active crossovers, and sum the channels back together after being filtered and then amplified, you get all sorts of phasing problems around the corner frequencies, and while you can de-EQ the response (CleanSweep, 360, etc), I (and many other pros) just don't think you will ever get Humpty-Dumpty back together again. It just does not sound as good as a clean preamp full-range signal.

There is not ANY car that I would prefer us to use the speaker level outputs rather than the preamp level outputs, given a choice. (Some cars have fiber optic amp links, or analog preamp signals that don't vary with volume, etc., etc.)

Now, we at my shop don't just guarantee you won't have noise. We guarantee that you will love your system's sound or we will take out the entire installation, make it all stock again, and refund all your money. When I make a decision about how to do an interface, I'm guaranteeing that it will be noise-free AND it will sound great. I would say 80% of the systems we do use the OEM HU, and we don't get noise, and we've used speaker level twice in the last year, and once we had noise until we found a way to eliminate the speaker level Navone LOCs and go preamp level.

This whole speaker-level myth reminds me of bees not being able to fly, or fireplaces making houses colder.