Quote:
Originally Posted by shern
Randy P
I just helped a buddy install an Alpine HU into his SC with the Metra harness. I have EXACTLY the same issue you describe. As soon as you power up the radio, there is a buzz, even when the car is not running. And then alternator whine. Pull the RCAs and it's gone.
I suspect some sort of ground loop between the HU and the factory amp. I noticed that the signal grounds and the chassis ground are connected. I'm a bit stumped. If somebody has some insight, please chime in.
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The noise is because the ground reference points are so far off due to impedance differences between the inputs / outputs. Metra did a crappy job on this harness. We could probably just simply hook up the speaker + on ecah corner to the harness and it'll probably give us less problems, but I don't feel like risking damaging my deck to see if it works.
Used to work on other cars (like OEM BMW) that way.
It's not worth screwing with, bypass the amp. It's $11 in speaker wire and the quickest answer. You'll spend all day fooling with changing grounds, etc etc total waste of a day, plus you aren't risking burning up your HU outputs. The harness in the trunk is even long enough you can stand outside and cut it. Pretty sweet.
Quote:
Originally Posted by 2turbo1sup
RANDYP; I should try that method and put the sub and speaker amp back into the car. I'll try it after I get off work and post my results. Question: did you splice in power to the sub amp harness on the back of the HU?
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Nope, behind the dash the only harness off the original radio that is being used is the one the Metra plugs into. The other harnesses, including the dedicated sub harness are just sitting there.
I'm sure someone out there will insist removing the factory amp and running all this wire is the answer but this is the fastest, neatest and is the least amount of butchery to get it to work. I can return my car to full stock in under 30 minutes if I need to.
rjp