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Old 10-03-2009, 06:22 PM   #1
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Aftermarket Head Unit wiring help

I'm in the process of trying to replace my dead CR-220 with a JVC CD head unit. My '02 S has the Bose system with dash/door speakers and the front trunk-mounted amp. The plan is to keep the amp and replace the speakers shortly after the head unit.

The JVC & model 70-1787 harness were purchased from Crutchfield. I carefully wired everything up and the speakers didn't work. After some research online, I quickly came to the conclusion that I need a 70-1784 harness to get the proper speaker connections.

The JVC has both speaker level outputs and 2 pairs of RCA line level outs. Which ones should I be wiring up to my adapter harness? I can't tell whether the old Becker's outs were speaker or line level. I thought most amps like line level.

Thanks,

Gary
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Old 10-04-2009, 04:19 AM   #2
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you need to wire the line level outputs from the new h/u to the amp. The OEM wiring harness uses a common ground for all 4 channels. Make sure you also connect the remote amp turn on from the new h/u for the amp. If you're uncertain which wire is/belongs to which from the old set up, you can download the owners manual for your old CR-220 directly from http://www.beckerautosound.com/Porsche/Porsche%20Menu.html Near the back of the manual there is a schematic of the back of the h/u which you can cross ref w/ the wiring harness plugs.

Good luck
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Old 10-04-2009, 12:58 PM   #3
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After my post I found this Becker h/u diagram you also referred me to.

All of my factory speaker connections are in the brown plug (socket B), which are the speaker level outputs. My factory wiring for socket C (yellow plug) line level outputs has no speaker connections, just a ground wire, as I recall. So it looks like the speaker level outputs were going from the Becker to the factory amp, which doesn't seem to make sense.

It's been many years since I've installed a stereo, but I always thought amps took line level inputs because the unamplified signal's cleaner. Crutchfield's instructions also explicitly say to use the RCA line level outputs. So I guess I'm going to rig up the new h/u line outs to the adapter harness and see how it goes. I'll report back whatever I come up with.

I welcome comments from anyone else who's been through this or had similar experience.

Thanks,
Gary
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Old 10-04-2009, 01:13 PM   #4
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Might the new h/u require line level outputs be turned on during a set up function?
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Old 10-04-2009, 01:15 PM   #5
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I used to do some installations, I recall some amps were designed to take speaker level inputs. If that is the case with the Becker, you should be able to use the speaker outs on the JVC , unless the output numbers are crazy different. Can you trace back from the amp and verify the origin of the connections to the Becker H/U?

edit* stated more simply, if the only connections to speakers out of the Becker H/U are amplified then it would seem to indicate the under hood amp takes a pre amped signal.

Last edited by eightsandaces; 10-04-2009 at 01:22 PM.
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Old 10-04-2009, 01:34 PM   #6
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Truthfully, I paid the $50 to let the BB guy do mine. They are insured and if they screw something up they have deep enough pockets to fix it. I also bought a JVC HD50?? something. It wasn't the easiest install as he had to use a second wiring harness. He commented that the fronts and doors shared a common ground. the rears were not hooked to the amp but to the Headunit and now they blow the amp speakers away. I have to adjust the fade to 2 or 3 (front) to get the sound evened out.


Quote:
Originally Posted by gschotland
I'm in the process of trying to replace my dead CR-220 with a JVC CD head unit. My '02 S has the Bose system with dash/door speakers and the front trunk-mounted amp. The plan is to keep the amp and replace the speakers shortly after the head unit.

The JVC & model 70-1787 harness were purchased from Crutchfield. I carefully wired everything up and the speakers didn't work. After some research online, I quickly came to the conclusion that I need a 70-1784 harness to get the proper speaker connections.

The JVC has both speaker level outputs and 2 pairs of RCA line level outs. Which ones should I be wiring up to my adapter harness? I can't tell whether the old Becker's outs were speaker or line level. I thought most amps like line level.

Thanks,

Gary
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Old 10-04-2009, 07:56 PM   #7
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Problem solved, I think.

The JVC h/u has two sets of RCA line level outs, one pr of full range marked "front" and one pr for the separately powered subwoofer, which I don't have. (BTW, the JVC has no fader control, so no need for front and rear RCAs.) I cut the ends off the full range RCAs from the adapter harness and wired them up to the other adapter harness connector for the front speakers, which plugs into the brown factory connector ("B" in the diagram below) that has all 4 speaker connections.

Doing this I thought I'd get sound out of the dash speakers only, but instead got it out of all the speakers, including the factory sub behind the seats,all connected to my factory amp. Even with the crap factory speakers the sound is considerably better. Love the HD Radio. The dash speakers are being replaced with Focal 100 CVX coaxials later this week. I'm really looking forward to what I expect will be an additional major improvement. When I have some more time I'll be putting 6.5" Focal woofers in the doors.

Thanks Burg Boxster for confirming what I thought about using the line outs instead of the speaker level outs, and everyone else for their helpful insight. I was expecting a simple plug-in installation with the harness from Crutchfield. This one required a little more thought and know how.

Gary
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