Amp grounding
 

I decided to gut the stock sound system on my 08 2dr X. New H/U, 4 speakers and amplifier. I have a powered sub on order and should be here and installed by the end of the week

Components:

Kenwood KDC-BTU558U head unit
Pyle PLMRA400 marine amp (waterproof)
Kicker 77K10 (all four) soundbar and front boxes stuffed with poly
Kenwood KSC-SW11 powered sub

I installed the amp under the drivers seat and noticed an existing bolt for grounding. I used about a 4" cable from the amp to that stub for ground. I am getting a slight hum in my speakers when the engine is running but it doesn't change with engine rev. Grounding problem?

Secondly, my H/U comes with a blue/white lead specifically for turning the amp on and off. I connected the amp to this lead and it did nothing, amp would not turn on. It is powered with the supplied power cable straight to the battery. I instead attached the on/off lead from the amp to the same lead that powers the head unit when the key is on, this worked no problem.

Everything sounds good and appears to be working correctly minus the speaker hum and even that's not terrible but I find it a tad annoying. So do I just have a grounding issue, multiple issues or maybe my amp is a Pyle (pile)

Any suggestions would be appreciated. Thanks

Try grounding to a different place. Try a bolt for the seat, or better yet, pull the carpet up grind down a spot and put a bolt through the floor. That should be your best bet. I would try to ground in different locations first. You can also run a ground from your head unit to your ground for your amp. If all else fails try a ground loop isolator.

Your rcas should not be ran close to your power wire as well. Keep them as far away as possible until you get to the amp. You could have a bad grounding issue, bad rcas, or wires too close to one another causing an interference.

Disconnect both RCA cables from the amp. Switch on the HU and listen for the noise. If noise is present adjust the amplifier gain controls to a lower setting. Noise still there ? Choose another clean rust free and no paint grounding point. After all this if noise is still there replace RCA cables with better quality brand. Running a ground wire from the HU to the amp grounding point will probably cause a ground loop and make the noise louder.

The remote turn on wire at the HU must give +12V DC. Some HU are able to supply the remote on voltage but with very little current (amperes). Suggest you use a booster relay on the blue/white wire leading to the remote on terminal at the amp. Good luck

Two things.
1st. Pyle ? Could you have possibly found a worse designed amp? The thing will NEVER be noise free. Never ever. It is only "marine" because it's painted white and comes with stainless steel screws. It is no more "water proof" or "water resistant" than a bread toaster.
2nd. Kenwood is notorious for having the blue (power antenna lead) and the blue/white (amp remote lead) backwards. I have seen hundreds of Kenwoods that when wire with conventional wisdom, the amp is only on when in tuner mode. Might be something to check.

The hum. It is most likely (99.9% sure) NOT a ground with the amp. But it is a bad RCA ground on either the radio side or the amp input. Not exactly an RCA CABLE ISSUE. The problem could be the radio, amp, or the cable. Or a combination. Non of which will be cured with moving a ground on the amp. The issue isn't a bad ground on the power supply of the amp. It is a huge difference of ground potential between the signal source and the input stage of the amp.

Easy test. Take a long piece of wire and touch it to the ground shield (outside ring of the RCA at the back of radio) and the ground shield of the RCA at the amp. Noise still there?

Also try this. Take an old RCA and cut the end (plug part ) off. Strip back the inner and outer wiring jackets on the plug part and twist them together. Then pug the "shorted" RCA into the amp. This will simulate a "0" bit signal, or full power muted signal. Any noise still there is certainly caused by the amp. If it's quiet. Plug in the RCAs to the amp input and move the "shorted" plug the the end of the RCA behind the radio. Noise? It's the RCA cables. None still. It's the radio. Process of elimination.

Also, wiring the power on one side and signal on the other side of the Jeep isn't going to matter. Not even a tiny bit. The "old wives tale" is it helps eliminate noise. But, what people don't see (forest for the trees thing) is that the entire Jeep is part of the power supply ground plane. And power flows from negative to positive. You would have to hover the amp outside the Jeep and hover the wires along with it. Haha. Most decent equipment made in the last 30-40 years has appropriate noise shielding built in to prevent radiated noise. Pyle might not. Haha. But should.

Update. 99.9999999999% sure it's RCA ground noise.

Thanks for the suggestions, plenty of things to try to isolate. I will post either a photo of me pulling my hair out or results of locating the problem

Where do you have your RCA cables ran?

from head unit back behind steering wheel and along drivers door under carpet and plastic. Power wire to amp is run from passenger side firewall then under center console to amp

I disco'd the RCA lines individually and the hum seems to come predominantly from the front output but there is some slight noise when the rear is isolated. Funny thing is when I turned up the gain on both channels the hum was quieter. I haven't checked the ground yet because I need to pull the seat. Fortunately if it turns out to be a shitty amp, I didn't spend a ton of coin on it

I only ask because RCA cables are notorious for picking up on any power cable, maybe swap out your RCAs with different ones, after that check your amps tuning