Noise elimination help please (car audio)

[den911]

Hi, i have a Sony aftermarket HU and a Alpine amp prior to this i had a Pioneer HU and a Pioneer amp, all equipment was brand new..
Having everything set up i was getting a lot of noise coming from channel B on the amp on both set ups ,Sony and Pioneer ..basically only happening when i plug in RCA to channel B .
Having only channel A running all was fine but as soon as you plug in the B channel RCA i get the noise ..I have separate power from the RCA and speakers down different sides of the car ,also changed and tried different RCA cables ,also tried moving ground from factory ground to making my own in wheel well, still the same..I have tried running a ground from HU direct to a factory ground that didn't work ...This morning i plugged my phone via a 3.5 jack to two RCA and plugged in to B channel on the amp started engine and i don't get any noise ,would this tell me it's the HU or amp ,just getting confused with it all now ..
PS The noise i get is a humm through speakers when idling also if i use indicator noise is prominent also when i hit the brake i can hear a noise through speaker ,this led me to think it could be electrical so i tried a power in line filter ,one wire to ignition, one to constant 12v and earth not solved still the same ..If anyone can add anything to how or knows anything else i could try it would be appreciated .Thanks

 

[AlS3BE]

Are you using a unit to take speaker outputs to rca or direct rca to rca from hu to amp?
Noise is a pain to track but it looks like you have tried everything like line filters earth points etc. Always found in line filters didn’t work for me in the past.
I remember in my old car I had something similar and took ages to sort, was running 3 Amps, 2 15” subs, components all round. In the end I got an earthing kit which created extra earth from battery to engine block, body and other metal places and this took all the noise away. The factory earth strap could be a corroded mess but still good enough for other things so I think these extra earth points helped its cause.
Easy enough thing make up yourself, some o clips and thick ish wires.

 

[den911]

Hi yes RCA from HU to Amp .
A ground loop isolator fixes the issue but it's only a plaster really would like to get to the problem.
I have a service due so while i have it jacked up i will se if the earthing strap is in good condition ..

 

[aqibi2000]

You’re issue IS inherany a ground loop.

This is proven since used your mobile phone to the RCA (phone is not connected to the vehicle ground since it uses its own battery) and there therefore no loop created, you had no sound issue

Hence using a headunit which shares the same power connections as the amplifier you have your issue.


2 questions:

1) using an jump lead cable connected directly to the grounded body of the headunit and the other side to the body of your amplifier, does the issue continue (whilst ignition on, engine not running)?

2) is the issue only present when the engine is running, not when only at ignition on (KL15)?

 

[den911]

Many thanks for taking time to reply , i have tried the HU ground to Car body ground and i still get the issue, also this only occurs when the engine is running ..What i also find strange is if i only use front Channel from HU to amp via rca all is fine ,but as soon as i add the second set of rca from HU to amp i get noise .

 

[aqibi2000]

Can you ground the amplifier directly to the hu using a jump lead just for testing purposes.

this is a common issue of noise suppression on alternator whine but sounds like you also have the RCA cable problems separately too.

have you used twisted pair RCA cable not just changing the cable

 

[den911]

Hi , will try Amp to HU ground, i am not using twisted RCA to be honest i didn't think that would make a lot of difference ,but you never know .
At the moment i am on 8 gauge for both Amp and Ground ,i have some 8 gauge to 4 gauge reducers on order so will try 4 gauge all round next .