Engine whine & hissing with a twist

[jamesw41985]

Got me beat.

Ever since moving battery to boot get horrible engine whine through speakers. Had a bit of a mess on today and it is as follows. I have 2 amps (one for components and one for subs). Im only hearing the problem through the one for componenets, maybe the problem is there on the subs but just cant hear the high freq.

The noise occurs when ignition is turned all the way on (is fine on first 2 clicks, and when car is running it changes pitch with RPM. The whine occurs even when HU on mute so is obviously not the headunit at fault. I have tried just having front left RCA plugged into chan1 on the amp and I get no whine at all. Ok so tried front left in chan2 - again no whine. Then tried front right in both channels and still no whine! The problem only occurs when both front left + front right RCA's are plugged into the amp.

Anyone any idedea's whats going on - I could undestand it if it was on one or both of the RCA's but its only happening when they are both plugged in at same time //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

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[jamesw41985]

Had a bit more of a mess on. Tried the RCA's going to the sub amp, and as i suspected the hissing and whine is there but obviously cant hear it due to the low pass filter and the fact its coming out of a sub. Hopefully get a good look @ it nxt weekend, have bodged it by using a spare rca splitter to split the right chanel, so im stuck with mono until I find out whats going on....

 

[jrwalte 10+ year member]

Just because whine still occurs when HU is muted doesn't mean it isn't coming through the HU. It can still have an active signal going through the RCAs, which would allow the noise to pass through.

What HU?

 

[jamesw41985]

Old Sony MP30

 

[helotaxi 5,000+ posts]

The noise is coming from the HU but isn't really a problem with the HU but rather it's ground. Using a heavy gauge wire ground the HU to the same point as the amps. This should minimize or eliminate the problem.

When you moved the battery to the rear, you made the ground for the amps better and the ground for the HU worse because the amount of chassis between the battery and each of those components changed significantly. The single RCA plugged in isn't enough to equalize the differential but the two together are which explains the noise only when both are plugged in.

I would also suggest regrounding th engine block and running a dedicated wire from the battery to the same point that you ground the block. That will take care of 2 of the big 3 and the + wire you took care of when you moved the battery to begin with.