Noise occuring only after installing second set of RCA's..

[asmox]

I recently replaced a JVC HU (with rear RCA outs only) w/ a Pioneer DEH-P4600MP (with dual RCA outs).

Now, prior to the switch I had the one RCA cable running to my amp (Power Acoustik LT-960/4) with two RCA splitters on the end in order to be able to play all four speakers.. though only on the rear signal, meaning that fading to the front was impossible - but everything else worked perfectly.

Now I replaced the HU, ran a second RCA cable and hooked it up.. instant engine interference. The noise only occurs if I have both RCA cables plugged in to the amp. One cable with two splitters doesn't produce any noise, and switching the cables around doesn't produce any noise either (meaning that the new cable isn't bad or anything). Noise ONLY occurs when a second RCA set is plugged in to the amp.

I'm sorta confused, any ideas..?

edit: btw, the noise is in the form of static when only the accessories are turned on.. but turns into the classic high pitched whine when i start the car. the noise only occurs on channels 3/4.. but like i said, everything works fine with a pair of rca splitters running into all 4 channels with 1 rca cable.. but noise appears only when i use a whole other physical rca cable in conjuction with the first one.

[duckfart]

I have the same problem !!!!

[Slody4Futbol]

figure out if it's from the front or rear section of ur head unit... plug a set from ur rear preouts into channels 1 & 2... start the car... turn everything off and plug them into 3 & 4... start car... turn everything off... plug rca's into the front preouts... and plug into channels 1 & 2... then 3 & 4... was it only on the front or rear?

[Slody4Futbol]

oh yeah reground your headunit... and make sure the ground on the amps is good as well

[tRiGgEr]

figure out if it's from the front or rear section of ur head unit... plug a set from ur rear preouts into channels 1 & 2... start the car... turn everything off and plug them into 3 & 4... start car... turn everything off... plug rca's into the front preouts... and plug into channels 1 & 2... then 3 & 4... was it only on the front or rear?

It's not from a certain preout. Sounds like it is any given one, depending on which one he plugs in first.

I had that problem on my 4 channel amp. So I set the signal to split on the amp. A month later I re-plugged them in. No more noise???

[mezman001]

make sure that new ground is as far from HU as possible it will give a whine if too close to HU

[maylar]

I have the same problem with my Pioneer 6400. One set of preouts hooked up, no noise... add a second set, get noise. Doesn't matter which set comes first.

I've redone the grounds over and over with no change. However.. remove the HU from my (metal) dash and the noise goes away. It's gotta be ground related and it's a friggin Pioneer thing.

My nephew solved his engine whine (also Pioneer) by making up little inline cables that let him ground the RCA shield right by the HU. I'm gonna try that.

[knukonceptz]

If there is a difference in voltage between the HU and Amp you can possibly get noise. The differnce in voltage would indicate their is more resistance to one of the components and the RCA's ground conductor is providing a lower resistance to one of the component's grounds. This is why I recommend you connect the amp and HU ground at the same point, both items get the exact same voltage from the same source. If you still have noise I would be shocked. Run 10 gauge speaker wire from a dist block in the rear (with + and -) wire directly to the HU. Do NOT use the car's harness for power/ground, just connect the IGN lead on the harness

Unplug your RCA's at the HU while you have noise present in the system. If it is still there without signal then yes the RCA's are absorbing noise. My Guess, when you unplug the RCA's at the HU you will not have noise. Leading to the ground loop...

Check Batt Voltage, Voltage at amp and at back of HU just to see if there is a differance.

Pioneer - are known for ground loops due to design of the output section

[maylar]

All of that is good advice. However the situation in my particular vehicle is a bit non-standard in that the HU is also grounded to the dash via its case. Location of the ground wire is insignificant. I suppose I could try running the amp ground up to the front and grounding it to the HU case... I bet that would work. But uggh what a pita that'd be.

[knukonceptz]

Dont change the amp ground point, change the HU ground point. The metal dash is probably not helping, but if you have a less resistive path by using the 10 gauge speaker wire to power the HU it should clear out the noise from the RCA.

Can you wrap the outer mounting sleeve with e-tape at the contact points to maybe isoloate the HU from the dash?



edit - why was this dug up anyway.... 2 years old??

[maylar]

LOL I didn't even notice the age of the first post. The noob musta dug it up. It's still relavent to my install tho.

My HU installs with custom made brackets in the 80's GM dash opening. Original radio had shafts. No way in hell to isolate the chassis. I know that Schoshe (sp) makes plastic mounting boxes but the front dash trim panel has been modified to fit what I have and I don't want to revisit that.

http://pages.cthome.net/davecullen/installed_hu.jpg
http://pages.cthome.net/davecullen/pioneer_hu.jpg

I'm currently cheating by using special RCA's for the sub channels that have no shield connection at the amp. Still have a tiny bit of engine whine in the front channels but it's acceptable. My next HU won't be a Pioneer.

[puregunpoore06]

yea i have a pioneer 2 and i have the same **** problem... so i just fix the grounds???