I had an amp fitted the other day and some speakers.... i get a whineing noise like something is working in the engine when its turned on? i only noticed it when i turned the volume down.. its very noticeable.... it seems to get louder when i accelerate. If i turn the head unit off the whine goes... could the amp be drawing too much power and what ever charges the battery is kicking in?

is it bad for the alternator?

 

The whine is most likely the result of a ground loop. If you had a shop do the install, you should go back and have them reground everything. If you did the install yourself, go back and reground everything...

 

can you tell me a bit more info mate on what is causing it? is it a bad earth? is it noise coming through the speakers? is it a power cable too close to the rca and then i can hear it through the speakers?

I am not sure if its coming through the speakers as i have turned the volume way down......

 

There are 3 (4 if you have 2 amps) ground (earth) points in your audio system: the battery ground, head unit ground, and each amplifier ground. A ground loop is caused when any two of these are not the same (a resistance of > 4ohms is present between the points). Because the grounds are not the same, a voltage is present when the stereo is turned on. This voltage causes a current to flow between the ground points. The whine is your speakers reproducing this current (speakers convert audio signals from current into audio waves).

Your ground points should be free of paint. Contrary to a popular belief in these forums, your ground point should also be a dedicated point (not just an existing bolt) - as in, get out the dremel and clean off ALL the layers of paint and rust inhibitor around a point close to the amplifier. Once an area about the size of your thumbnail is clean, drill a hole directly in the center of the clean spot. Use a sheet metal screw to attach your ground wire to this point. The ground is made through the contact between the threads and the sheetmetal and the wire terminal and sheetmetal. For best results, drill the hole, get out your tap set, tap the sheetmetal, and use a brass screw.


The ground wire between your battery negative terminal and the firewall needs to be at least the same gauge as the power wire leading to your amplifier(s).

 

what kind of head unit are you using?

 

9.5 Times out of 10, it's a ground issue. The other .5 is due to the power wire running parallel to the RCA wire for too long of a distance. NP is correct in his posts.

 

JVC AVX44 headunit...

I think its a ground issue... Other wise I wouldn't hear the alternator!

 

It's a ground.

 

They sorted the issue with a noise supressor. Do these affect audio quality? Would you lose some base etc? I am pleased with the sound coming out but I thought it might need a bit more base... I had spent all day waiting in an audio shop who were playing lots of music with subs attached.. I can't tell if thats why it sounds like its not as basey?

The other problem is now.. They broke the headunit... They are going to replace it ... The connector to the face off has a bad connection as it flicks on and off if you press it... It was all working fine till i asked them to drill the brackets so i could shut the radio door.. I think he used a little bit too much force on the headunit... It still plays music and sits behind the radio door so I am not bothered.... Sometimes the screen is on sometimes its not.... They are willing to sort it out though and the guy installing it is a nice guy so didn't get angry...

I have to go back in a couple of weeks as thats my 1st day off! 4th time lucky?

 

A noise suppressor simply covers over a bad ground and should only be used as a troubleshooting tool, never a permanent fix. CHECK YOUR GROUNDS. PLEASE.

Noise suppressors affect sound negatively as well as cover over a serious issue - your grounds are likely bad.

You shouldn't have to drill anything to get the bracket positioned to fit the HU with the door closed.