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Discussion Starter · #1 ·
i originally had xtant a4004 and a3001 wired with 8 gauge power and ground, no noise at all.

i needed some space for other stuff, so looked to get some alpine pdx amps. i tested a pdx-4.100 with the old wires already in place and it sounded fine, no noise.

however, the original 8 gauge ground is a bit too short for proper amp mounting, and manual also seems to indicate 4 gauge wire is more optimal. so i went with 4 gauge power and ground wires.

after all 4 gauge wires are installed, ran the system, and some high pitched noise appeared. weird, wasn't there when the pdx was simply test fitted. so i double checked the ground, sanded the area a bit more, and re-tried it. still some noise.

i went back and tested the xtant a4004, with the new 4 gauge wires -- no noise.

so now i'm kinda stumped.. i went ahead with the pdx cuz my first test didn't have any noise. i know the pdx rated thd isn't the greatest, that's why i tested it first. but it seems as tho there is now some high pitched noise i'm not sure how to get rid of.

any ideas? thanx!
 

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Discussion Starter · #3 ·
weird thing is i didn't hear it the first time i test fitted the alpine.

so i checked some things and noticed that there is no hissing without the rca plugged in. the cables don't cross with the power/ground, one is routed in front and one is routed behind the amp. is it possible that the pdx picks up this rca (or wherever it's from) noise while the xtant doesn't?
 

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Discussion Starter · #5 ·
moved the rca (monster micro xln) around to test.. it's not crossing anything, it's kinda just running straight in the middle of the cabin :), like a clothes line, from the hu to the amp. a couple of panels are off, so just imagine if the rca cable is coming out from the hu, between the passengers, and into the amp.

same high pitched noise, regardless of the volume, or if the hu (pioneer avic d2) is on "source off".

i checked the connections behind the hu, everything appears to be snug. but when i touch the rca connectors behind the hu where the monster cable meets up while they are connected, sometimes, some of the noise dissappears (not all), and other times, the noise gets stronger.. almost as if i'm the ground

the odd thing is the xtant never picked up this noise; i guess that's a/b vs d amps? so, what can i do to reduce this noise?
 

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Make sure your RCA's at the amp aren't pushed so far in that they touch the back panel of the amp itself.
 

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Discussion Starter · #7 ·
seems as tho the problem starts with at the front where the rca cable is connected to the head unit. slight jiggle creates more/less noise, but never completely gone. tighted the male plugs a bit so they fit more snugly onto the female plugs, the noise is more constant, no more on/off by the slight jiggle..

found an old noise suppression unit from monster that runs inline on the rca, plugged it in. viola! no high pitched noise anymore.. very happy :D. altho taking apart the whole right side of the car to move the patch cables was a big pita... at least i know it's not a problem of cable location.

now i just need two more noise suppression units for the rear and sub channels.



interesting to note that the xtant didn't have this issue. perhaps the pdx is a bit more sensitive and/or requires a cleaner signal because of it's higher thd rating.

anyway, hope this helps someone in the future
 

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The HU should ground the RCA and may not be doing it. Different amps do different things with the RCA ground; they can't ground it or it will make a ground loop but they do something with it to help with noise. But if you don't have ground on shields of unbalanced RCA through the HU you have a problem.
 

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my pdx does it to..

but is not a hiss its like a weird noise, just when the volume is low...

once i turn the volume up, it dissapears, and it just appears again if i turn off the HU.
 
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