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Discussion Starter #1
Alright, so I just finished adding a new amp and rewiring a few things. I have a boston Gt2200 for my front comps and now a newly installed boston Gt2125 for my rear coaxes. After connecting the rca's to my rear amp, I get very noticable alternator whine and other noise. The noise is only noticable when both amps' rca's are connected. Now, before you say bad cables, bad ground, or bad amp-

I am using a 4 channel rca cable by knukoncepts--reasonable quality wire. I bought this cable back in the day to replace two separate two channel rca cables which were feeding a Polk PA660. Before buying this cable, there was noise present when both sets of rca's were connected. If one set was unplugged, things were fine. Thus, I reasoned that it had to be some sort of issue regarding whatever characteristics differed between the two sets of rca's creating some sort of ground loop. So I bought the four channel cable and fixed things instantly.

Now, this comes back to haunt me. In my current setup, the two Boston amps are mounted some distance from eachother. Because of this, I am forced to use a short rca extension cable on two of the four channels of my rca cable. And thus the noise is back. At this point, I am fairly certain that the noise is exclusively due to some sort of inconsistency among the rca channels. Perhaps it is not something that can be fixed without removing the extension, but I'd at least like to comprehend why the problem is occurring.
 

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First read through the following discussion, there is some great advice about whine and noise issues: http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/2977-troubleshooting-noise-whats-next.html

Whine is almost always caused by a ground loop and/or poor ground (power or signal).

Go through the system and check all ground points - make sure you have shiny, bare metal chassis ground points for all audio equipment. Check your "Big Three" connections.

Make sure you tape the RCA ground rings where you added the extension cables if they are exposed (you only want the RCA cables grounded at the source and destination points.

What head-unit are you using? Make sure it is well grounded too.
 

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Discussion Starter #3
I'm actually using a pioneer DEH80PRS, so I was thinking that maybe I should look into it being a pico fuse like problem. From what I've read, in the 80PRS the pico fuse has been replaced by a capacitor which is only slightly more resilient to being destroyed in the event of hot swapping rca cables. I've searched around and found almost nothing about opening an 80PRS to solder and fix the problem. Does anyone know if that's still possible, or is using bare wire to ground the rca's to the deck my only option?

By the way, I remounted the amps and eliminated most of the noise, but some is still there. I guess Ill try grounding the rca's later this week.
 
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