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Hello all. First, I do not have an ST but I do have a 2016 Focus SE with the 4 inch screen and I am hoping to get some help with an audio issue. I apologize in advance for the long post but I want to put down as much information as I can. A few months ago I installed a Memphis Audio 16-PR 100.4 4 channel amp.

Since then I have had alternator whine and a buzzing noise that increases when I depress the brake pedal and also when I use the turn signals. At first I bolted the amp to the back of the left rear seat. Then I bolted the amp to a piece of MDF and then to the seat back. Then I moved the amp to the trunk.

I used a CARAV harness and then a European version behind the head unit to a 4 channel PAC LOC and ran RCA's to amp. I then replaced the PAC LOC with an active NVX XPLOC4. There is a module behind the head unit so I thought that might be causing the interference. So I put the NVX XPLOC4 in the trunk and ran Stinger 9 wire from the T-harness behind the head unit.

I removed the T-harness from behind the head unit and spliced directly into the factory harness speaker wires (I know I know) and used the 9 wire. I believe the speaker wire from the amp to the factory harness is 16 gauge which should be plenty since the amp is only 50 watts RMS/ 100 watts peak.

I ran a ground wire directly from the battery to the distribution block. Disconnected that ground wire and ran a 4 gauge ground wire from a spot I cleaned in the trunk area. Ran a new 4 gauge power wire. I used new RCA cables. Stinger 9 wire and speaker wire are under the sill plates on the driver side. Power and ground on the passenger side.

After doing all that, the whining and buzzing has NOT gone away. At this point I don't know what else to try. I'm thinking it might be the amp but I used the same amp with the PAC LOC in a 2017 F150 I used to have and it worked great. No noise, whine or buzzing. Again, I apologize for the long post. I know there are audio gurus out there. Thank you in advance for any and all help.
 

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Welcome to the forum.

Noise in the audio system can be extremely frustrating. The majority of noise is the result of poor or multiple grounds. But noise can be injected from other sources as well.

You mentioned that the issue only seems to occur when the brake / turn signals are in use? You wouldn't happen to be using aftermarket LED's in place of the standard halogens?

If you are do they have internal resistors or have you installed individual one in parallel to the bulbs?

J
 
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Can you disconnect the LOC via rca to the amp and drive around and see if the sound/buzzing persists?

just to see if the annoyance is stemming from theLOC side or amp side.

grounds should be short. Like under 24” short. Short ground and then if you need it use a distribution block.
 

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Discussion Starter #4
Welcome to the forum.

Noise in the audio system can be extremely frustrating. The majority of noise is the result of poor or multiple grounds. But noise can be injected from other sources as well.

You mentioned that the issue only seems to occur when the brake / turn signals are in use? You wouldn't happen to be using aftermarket LED's in place of the standard halogens?

If you are do they have internal resistors or have you installed individual one in parallel to the bulbs?

J
I am only using LED bulbs for the T10 driving lights, and interior dome, footwell, etc. Headlights and turn signals are factory.
 

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Discussion Starter #5
Can you disconnect the LOC via rca to the amp and drive around and see if the sound/buzzing persists?

just to see if the annoyance is stemming from theLOC side or amp side.

grounds should be short. Like under 24” short. Short ground and then if you need it use a distribution block.
I disconnected the RCAs one at a time from the LOC and from the amp. Still have the noise. The disconnected pair of RCAs have no noise. Connected pair do have noise. I forgot to mention in my original post that I had also cleaned off the paint at the main battery grounding point.
 

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Any butt connections? I had an issue with buzz when I went aftermarket in my truck. After chasing wires for a while, I ended up soldering and that eliminated the issue.
 

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I disconnected the RCAs one at a time from the LOC and from the amp. Still have the noise. The disconnected pair of RCAs have no noise. Connected pair do have noise. I forgot to mention in my original post that I had also cleaned off the paint at the main battery grounding point.
Just to be clear, if the RCA's are not connected to the amp, the noise disappears?

Have you tried a different set of RCA cables, or even checking the quality of the grounds for the LOC?
 

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Discussion Starter #8
I removed them when I removed the T-harness and used the 9 wire. Problem persisted.
 

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Just to be clear, if the RCA's are not connected to the amp, the noise disappears?

Have you tried a different set of RCA cables, or even checking the quality of the grounds for the LOC?
Correct. When I disconnect the RCAs from the LOC, the noise goes away but I have no audio. Same as when I disconnect the RCAs from the amp.
When I had the LOC behind the head unit, I used 2 pairs of new 17 foot (I think) RCAs. When I moved the LOC to the trunk, I used the same RCAs. I then bought a pair of new 2 or 3 foot RCAs. The noise level is the same.
As far as the ground wire, I order new 4 gauge wire that goes into a distribution block. I even ran it directly to the battery. The noise level is the same.
 

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Check out this thread. Exact same issue.

While I'm not sure a new wiring kit is the silver bullet, I do think changing grounds is.
 

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Thanks. I'll read through it. I have changed the ground locations from the main battery ground to the battery itself and lastly I just cleaned up a spot in the trunk. No change in noise level. Not worse not better. I'd hate to buy a new amp and have the same issue. There must be something I am missing. Thanks again.
 

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Check out this thread. Exact same issue.

While I'm not sure a new wiring kit is the silver bullet, I do think changing grounds is.
I read through the whole post. I have done just about the same thing in regards to the ground and the RCA. Second to the last entry, writer stated he replaced the power and ground wires with new ones (done that). He also stated that he installed a new amplifier. I'm thinking the problem was resolved with the amp replacement. My amp is about 15 years old, about the size of a Trapper keeper but has performed great. Maybe my amp's old school technology is not compatible with my car's "new" technology. I've ordered but not installed yet an Audio Control LC7i. I'm going to research an Audio Control 4 channel amp. Feel free to chime in with amp suggestions that have yielded great results. Thanks to all for your help. I'll update if I resolve the issue.
 

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Audiocontrol makes amps with their LOC technology built in. One single device. I hear their accubass feature is something amazing.
 

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If you already ran 9-wire top the back near the amp, then just get rid of the RCAs and the LOC and run the 9-wire directly to the amps built in LOC (the white connector next to the RCA inputs that says "high inputs")

another test is to turn the level adjustment up higher on the LOC and turn the gain on the amp down, my bet is that doing this will either reduce the noise or get rid of it completely.
 
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