Weird noise from amp

[VPFreak]

This is a strange one. I recently installed an amp in my 2010 SV6 also added new front speakers. The amp only runs the front speakers and has an inbuilt high level input so I ran the input straight from the speaker output.
The headunit is a IQ series 2 that I upgraded too.

Now I installed this about 2 weekends ago and everything was perfect. No interference noise from the engine or anything.
Drove it today and this morning was fine. Driving home (car got really hot parked in the sun) and now has a hum all the time. It’s worse if you turn the lights on. It doesn’t change with volume, so if the volume is on zero you can still hear it. Pull out the rca inputs at the the amp and the sound disappears. Tried running a new rca lead to the amp to the radio and sound returns. Any ideas what this could be a result off? No difference if the engine is running or not. Rear speakers from just the headunit are fine.

 

[losh1971]

Its probably a ground loop issue. One of the rca leads is not getting a proper ground. It could be the jack on the back of the head unit or one on the amp. I have had the exact issue before.

 

[VPFreak]

The strange thing is that it did work perfectly for 2 weeks then yesterday all of a sudden started making this noise. I am wondering if the amp may have become faulty?

 

[Anhevius]

You said it yourself in your first post, it got really hot. If the plugs weren't good quality, or older, the heat probably warped the metal out of shape and you've lost solid ground.

 

[losh1971]

The strange thing is that it did work perfectly for 2 weeks then yesterday all of a sudden started making this noise. I am wondering if the amp may have become faulty?

It can happen to a stereo that has been working for six months or more. You need to turn it on and unplug the RCA leads one plug at a time until the faulty one is found. It is a ground loop issue nothing more nothing less. There are three possible problems, the lead is faulty or one of the jacks on the HU is faulty or one of the jacks on the amp is faulty. Find the fault and I will tell you how to fix it if the issue is one of the jacks. Test the lead by swapping them over. Just don't connect them up backwards, + & - that is.

 

[losh1971]

If you think it's because the amp got hot in the car. Turn it on full on the amp itself and run it for 15mins with the vol right up, then put your hand on it. They are designed to get hot.

 

[VPFreak]

Just to be clear, this runs straight from the headunit (IQ) speaker wires. I joined these into a female rca plug. The rca cable plugs into these ( front left and right). From there it runs to the 2 channel amp. The amp is set to high level input and the gain on about 1/10. If I turn the gain up the buzz gets louder. If I pull out the right channel rca the buzz stops on the right, however is still on the left. If I do the same on the left the right channel still has the buzz.
I tried a different rca lead and it did exactly the same. The amp is an Orion cobalt. Sound doesn’t increase with volume it is always the same. The amp is only 2 weeks old. I am thinking of going back to where I got it and asking to wire in a new one to see if that is the issue.

 

[losh1971]

You can run a wire from a ground on the head unit to the RCA jack ground lead on the head unit using ring terminals and tape. If it has been installed by an installer then you could take it back. Be prepared though unless the RCA jacks on the amp are faulty it won't be covered under warranty. The other issue could be a poor ground on the antenna. You could try unplugging it and see if it goes away. Apologies for not explaining it better but it's easy to fix if I was there trying to put it in words aint easy. They might try to tell you, you need ground loop isolators, tell them that BS because if everything is grounded as it supposed to be you won't have the hum regardless. GLI's don't always work either.

 

[losh1971]

What do you mean IQ speaker wires? If you mean the speaker outputs from the HU that's wrong itself. You use a different type of amp plug doing it that way. RCA's leads are only there to give you a signal to the amp.

 

[losh1971]

If I am right in what I think you have done your signal wires should be connected to the high output wire jacks, not RCA's. From what I understand IIRC VE's have a shared ground for all the speakers. Without seeing it I am more than a little confused. I won't be much more help I incorrectly assumed you had connected RCA to RCA as is normal practice. The issue is still ground loop but without being there I could end up steering you in the wrong direction.