Nashville TJ's Build - Continued

This morning I cut all the wires to length, made sure everything was labeled correctly, and tinned all the bare wire connections. I also added a weatherpack connector for the amp trigger.

View attachment 304160

At that point it was all plug and play.

View attachment 304161

Turned everything on, looked for smoke (luckily none...🤗), and tested it out. Big difference in volume and clarity, and it drives the sub much better than it ever has before.

I am having an issue though - I'm getting some static when nothing is playing, and it increases and decreases with the volume. Not an issue that I've ever noticed before. I can really hear it when I turn the volume up high. I've checked all the connections, and walked through disconnecting all the input and outputs one at a time to see if it was any specific channel - with no change.

The manual for the amp recommended that the ground for the amp be in the same location as the ground for the head unit. They are not as the ground for the head unit is still in the stock location. Could that be creating the issue? Anything else I can check while I have access to everything?
Grounds are the number one place to check for noise. The amp guys will tell you to ground with the head unit because ideally there should be nothing else there to add noise. If you are using a shared ground you can isolate things and see if one of the shared items is the culprit.
 
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Grounds are the number one place to check for noise. The amp guys will tell you to ground with the head unit because ideally there should be nothing else there to add noise. If you are using a shared ground you can isolate things and see if one of the shared items is the culprit.
Since the ground for the amp is gigantic, would it make sense to move the ground for the head unit over to that grounding point?
 
Since the ground for the amp is gigantic, would it make sense to move the ground for the head unit over to that grounding point?
Not really. Just make sure the amp ground is clean and look for anything close that might be creating RF. From there check your connections between the amp and the head unit especially if they are RCA.
 
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Not really. Just make sure the amp ground is clean and look for anything close that might be creating RF. From there check your connections between the amp and the head unit especially if they are RCA.
I took a few minutes and ran a new ground wire directly to the battery to see if it made any difference, and it did not. I do have RCA pre-amp connections from the head unit, and I've checked all of those. When I disconnect the RCA's, the static does stop. I may try swapping those out.

The static is not bad, and I could certainly live with it, but it feels like there is something wrong that I'm missing.
 
Hmmm... Knowing you, you already have high quality audio grade rca cables, ie, they are shielded and twisted pair. Check to make sure they aren't looped around a power wire. Make sure they are fully engaged. Is it only one set? Like the front channels or rear channels? Can you isolate to one speaker?
 
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Hmmm... Knowing you, you already have high quality audio grade rca cables, ie, they are shielded and twisted pair. Check to make sure they aren't looped around a power wire. Make sure they are fully engaged. Is it only one set? Like the front channels or rear channels? Can you isolate to one speaker?
This^^. If the RCA’s are near the power wire you can get interference.
 
Hmmm... Knowing you, you already have high quality audio grade rca cables, ie, they are shielded and twisted pair. Check to make sure they aren't looped around a power wire. Make sure they are fully engaged. Is it only one set? Like the front channels or rear channels? Can you isolate to one speaker?
This^^. If the RCA’s are near the power wire you can get interference.
I thought about that too. They are decent cables - 3 of them - but I did try pulling the head unit out and running some different crazy large RCA cables from the head unit directly to the amp (not behind the dash). No difference at all.

I’ve also checked the gain settings on the amp, no difference there either.

I also checked to make sure the antenna wasn’t causing it by unplugging it. No change.

I’m thinking maybe I have a ground loop since the amp is grounded in a different spot than the head unit. I may try moving the head unit ground to the spot where I grounded the amp. Does that make any sense?

Anything else I can try?
 
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I thought about that too. They are descent cables - 3 of them - but I did try pulling the head unit out and running some different crazy large RCA cables from the head unit directly to the amp (not behind the dash). No difference at all.

I’ve also checked the gain settings on the amp, no difference there either.

I also checked to make sure the antenna wasn’t causing it by unplugging it. No change.

I’m thinking maybe I have a ground loop since the amp is grounded in a different spot than the head unit. I may try moving the head unit ground to the spot where I grounded the amp. Does that make any sense?

Anything else I can try?
Typically hiss is caused by a ground issue, so I think you're on the right track. I don't have my grounds tied together, and I don't have hiss, but ymmv.

I did try one of those factory one radios before I went with an aftermarket head unit. That thing had terrible hiss. It didn't have pre-amp outputs though, so I had to use high level input... Are you using speaker output to get the input for the amp? They are much more susceptible to noise. I ended up returning that radio, it was so bad.
 
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Typically hiss is caused by a ground issue, so I think you're on the right track. I don't have my grounds tired together, and I don't have hiss, but ymmv.

I did try one of those factory one radios before I went with an aftermarket head unit. That thing had terrible hiss. It didn't have pre-amp outputs though, so I had to use high level input... Are you using speaker output to get the input for the amp? They are much more susceptible to noise. I ended up returning that radio, it was so bad.
I’m using the pre-amp RCA outputs from the head unit. The ground swap will be easy since I still have everything apart. Couldn’t hurt to try at this point I guess.
 
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I’m using the pre-amp RCA outputs from the head unit. The ground swap will be easy since I still have everything apart. Couldn’t hurt to try at this point I guess.
The other possibility is that its just internal to the head unit. Doubtful, but it might just be old and passing interference. That would suck...
 
The other possibility is that its just internal to the head unit. Doubtful, but it might just be old and passing interference. That would suck...
It's a fairly new head unit, and there was no static before I installed the amp. Gotta be something I did - when I unplug the inputs at the amp, the static stops. Hopefully that means the amp is fine, but I don't know.
 
Well, I redid the head unit ground. Hacked into the harness once again and connected the two grounds to a length of 10 gauge.

Jeep - Stereo Amp 4 - 1-23-2022 (4).JPG


Added an eye...

Jeep - Stereo Amp 4 - 1-23-2022 (1).JPG


...and connected it to the same ground point as the amp.

Jeep - Stereo Amp 4 - 1-23-2022 (6).JPG


And no joy - the static is exactly the same. I'm at a loss as to what to try next.
 
Well, I redid the head unit ground. Hacked into the harness once again and connected the two grounds to a length of 10 gauge.

View attachment 304430

Added an eye...

View attachment 304431

...and connected it to the same ground point as the amp.

View attachment 304432

And no joy - the static is exactly the same. I'm at a loss as to what to try next.
Are you sure the power wire is not too close to RCA’s. Even with good shielding I wouldn’t trust it. I run power down the driver side door sill and the RCA’s under the center console.

Wish I could be there to help. Frustrating.
 
Are you sure the power wire is not too close to RCA’s. Even with good shielding I wouldn’t trust it. I run power down the driver side door sill and the RCA’s under the center console.

Wish I could be there to help. Frustrating.
They are separated by a few inches behind the dash. But, when I tested swapping RCA cables, they were separated by a good bit, and the static was still there. I may try moving things around again and see if it makes any difference.

The amp supports high and low level input, so I guess I could also try running speaker level input to the amp, although it feels like I’m grasping at straws now.
 
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They are separated by a few inches behind the dash. But, when I tested swapping RCA cables, they were separated by a good bit, and the static was still there. I may try moving things around again and see if it makes any difference.

The amp supports high and low level input, so I guess I could also try running speaker level input to the amp, although it feels like I’m grasping at straws now.
I'd suggest new RCAs before that. High level input are vastly inferior to a good RCA connection.

Go one RCA pair at a time. See if you can isolate the static to one channel.
 
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I'd suggest new RCAs before that. High level input are vastly inferior to a good RCA connection.

Go one RCA pair at a time. See if you can isolate the static to one channel.
I did a test using the high level input, and the same result - so no joy there either.

I also tried to swap the RCA cables again since the last time I did that was before I redid the ground connection. Same deal, no change. I even tried one channel at a time, swapping connections back and forth, to try to identify a bad channel. The static is the same no matter what I do.

On a whim I wired the + power connection directly to the battery to bypass the PDC. Same deal.

I've rechecked all my wiring to make sure I didn't cross something up, but I can't find anything.

Dammit.
 
I H8 wiring gremlins. Hang in there bud. We’re cheering for you.
 
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