[Wintermute]

Looking for some input on how to route my speaker cables to avoid alternator whine. I tapped into the front left and right door speakers for my amp inputs. They are run to a LOC converter and then to my amp (both in the trunk), and then back to the door speakers which are kicker 6x9’s (I am only using my door speakers and the front tweeters). Somewhere on the passenger side of the car, I am picking up an ENORMOUS amount of signal interference from the alternator, but also from other electrical accessories IE turn signals ect. I suspect it’s from the body harness that runs along the outside edge of the passenger side. I’ve tried to avoid it as much as possible but I’m still getting a pretty fair amount of noise, only when the engine is running though. I have an inline power filter installed between the battery and amp already. Amp is grounded to battery. Tried grounding to the body and it made no difference. Tried installing a ground loop isolator and it made no difference. Tried several different RCA cables, no difference. I have narrowed the source of noise down to the speaker level inputs between the speaker and LOC on the passenger side. At this point I am considering passing the passenger side cables over to the driver’s side under the dash and routing them back to the trunk that way.

CAR: 2020 LT1 base stereo option, no amp.
AMP: Alpine R-A60F
LOC: kicker 46kisloc2

[Msquared]

FWIW, I ran my both sides of speaker-level inputs to the trunk and the amp outputs back to the front on that passenger side too, and I get no alternator whine. The only difference was I tapped into both left and right signals at the radio module by the glovebox using a breakout harness instead of tapping the signals from each door speaker. That made my input run a lot shorter than yours. My car is a 2020 SS 1LE, which also has no factory amp in the trunk, same as yours. I assume the issue is on the input side picking up RFI, so I wonder if taking the signal from the radio module and running both channels of it down the passenger side like I did would help?

[Wintermute]

The passanger side is where it's picking up the noise.

[ctrlz]

I would try a test just moving the wires out of the trench, or wherever you think they are picking up the induced noise. If you move them even a few inches away from the suspected source, you should notice improvement.

So, it's A/C in the wiring that will induce noise. Common solutions would be using shielded wire, twisting non-shielded wire, or moving things. Less likely possibility is bad (shorted) diode in the alternator, which would probably manifest in ways beyond audio system trouble.

[keep_hope_alive]

It is a common misconception that speaker wire routing has any affect on alt whine. it does not. the speaker wires are after amplification and there is no EMI impacts on those wires that can result in whine.

Whine is the result of ground loops in the amplification or pre-amplification equipment. Items that can cause alt whine:

- metal chassis of amp or LOC in contact with vehicle metal (this can bypass any signal ground isolation)
- signal wiring from HU to LOC or Amp in has improper signal grounding
- LOC or Amp has excessive resistance (or impedance) between local grounding and source grounding

Usually, nicer equipment does not suffer from alt whine while cheaper equipment can (and does). It costs more to do balanced inputs or ground lift options.

[ctrlz]

Originally Posted by keep_hope_alive

It is a common misconception that speaker wire routing has any affect on alt whine. it does not. the speaker wires are after amplification and there is no EMI impacts on those wires that can result in whine.

Agree with keep, extremely unlikely at best. Think of the speaker wires for your home audio that often are laying next to AC extension cords.

[Wintermute]

Okay I believe you, so why would it only be picking up the noise when I plug in the RCA for the right hand passenger side if it's a grounding issue though? Not trying to argue just trying to figure out what I need to fix.

[Wintermute]

To clarify, I can play music through the left speakers with NO signal noise at all. The noise comes when I plug in the RCA for the right hand side into the amps input.

[keep_hope_alive]

Originally Posted by Wintermute

Okay I believe you, so why would it only be picking up the noise when I plug in the RCA for the right hand passenger side if it's a grounding issue though? Not trying to argue just trying to figure out what I need to fix.

You've tried a lot of good things so far and you have fine equipment. It is an annoying issue, to be sure.

Describe or post pictures of the install, please. Focus on the connections so they can be reviewed. Describe how splices were made, how connections were made, etc.

The connection of the RCA is what completes the ground "loop".

I haven't put the factory signal on a scope (yet) to see if it's balanced or unbalanced.

[keep_hope_alive]

Also, it greatly helps to keep the amp gains and LOC gains as close to minimum as possible. This is achieved by using most of the head unit signal level (use fader as needed to blend the rears). Noise is minimum when amp gains are minimum.

Delete the LOC. That amp has high level inputs. You don't need the LOC.

[Wintermute]

Deleted the LOC and the noise is 100% GONE. Thank you so much!!!!!

[ctrlz]

Originally Posted by keep_hope_alive

Delete the LOC. That amp has high level inputs. You don't need the LOC.

Another victory for following the instructions!
Hooray