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Interesting Info About Engine Noise I Found

nemz

By nemz,
in Car Audio & Electrical

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nemz Experienced

nemz

Posted
Posted

What's that weird motor noise I get with my portable CD player?

[JSC]

======================================================================

Many people report problems while playing CDs from a portable CD player

into their car audio systems. The problem, stated very simply, has to

do with the stepping of the motor requiring a varying amount of current

and non-isolated power and audio signal grounds. Using a liberal

application of capacitors and inductors, this voltage variance can be

restricted to a window of 8.990 to 9.005V for a 9V CD player, yet even

the swing between these two levels is enough to cause annoyingly loud

noise on the outputs. It has been reported that this entire problem

can be solved by using a true DC-DC inverter at the power input to the

CD player.

RANDY Veteran

RANDY

Posted
Posted (edited)

So the stepping in the motor that pushes the laser around or the motor that varies the spin speed of the disc draws various amounts of current.

My motor or alternator whine noise happens when I listen to the radio too.

I also beleive this only happens to people who run RCA cables to an amp? That's when mine did it, anyway.

Edited by RANDY
RANDY Veteran

RANDY

Posted
Posted

Tried that too. Tried running the RCA's completely out of the car, then into the boot. No change.

Earthing the RCA's helped about 50% at the time. You just run a wire from the outer contact to somewhere metal on the car. It got rid of the noise quite a bit, but it was still there.

The noise apparently comes in when either the HU or the amp isn't grounding the negative part of the RCA cable properly. These cables carry 2v or more in them, so plugging them in and out while everything is powered up can kill the grounding fuse or track in either your HU, amp, or both!

I opened my HU when I had this problem, and found the ground track was burnt through. I bridged it with some wire, tested with a multimeter and put it back in. No change at all. I suspect it's blown somewhere else too.

  • 2 weeks later...
J_Red33 Experienced

J_Red33

Posted
Posted

I've also got this problem & part of my trouble I believe is the stupid installers set the amp up with the rear speaker RCA connections to the amp jammed under the fuel pump relay. I have to rotate my amp the other way around, this will probably cure half my problem. But they also have not grounded the RCA's at the amp, so they had NFI (COMPLETE AUDIO U SUCK!)

sky_hi Contributor

sky_hi

Posted
Posted

grounding is always the problem here. it is caused from the wrong resistance termination on a end of line. for example i have no issues running cd or radio tuner. however i have a AUX which goes to a stereo lead so i can plug in ipods, phones etc to listen to music. because this line doesnt have a EOL resistance on it it humms with the alternator due to incorrect ground loop. easiest way to fix is u can get filters from a audio shop which u put at the speaker to filter out noise on ur grounding wire. just cut ur negative wire at the speaker and put it in just before the speaker. a capacitor would probably work as well assuming its big enough and doesnt explode. safer to get a proper kit from somewhere like jaycar.

J_Red33 Experienced

J_Red33

Posted
Posted (edited)
grounding is always the problem here. it is caused from the wrong resistance termination on a end of line. for example i have no issues running cd or radio tuner. however i have a AUX which goes to a stereo lead so i can plug in ipods, phones etc to listen to music. because this line doesnt have a EOL resistance on it it humms with the alternator due to incorrect ground loop. easiest way to fix is u can get filters from a audio shop which u put at the speaker to filter out noise on ur grounding wire. just cut ur negative wire at the speaker and put it in just before the speaker. a capacitor would probably work as well assuming its big enough and doesnt explode. safer to get a proper kit from somewhere like jaycar.

Installing filter caps on the speaker wires is an absolute last resort as this will also affect the sounds of the audio, & not really a solution to a problem that shouldn't be there. If your problem is on the input to the head unit then that's where it has to be fixed. You may need to change your lead set up on your auxillary to cure you're issues.

The problem with my set up, is that the RCA cables have got a ground wire that's meant to be connected at the head unit & the amp & it hasn't been done, so the input to the amp is effectively floating, doesn't have the same ground reference as the head unit & therefore highly susceptable to interfearance. Getting it away from the bloody fuel pump relay will also help in my case.

Edited by JazzaR33

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