how to eliminating alternator whine in car audio??

[BennyT]

ive got a shocking whine in my car audio atm which im pretty sure is alternator whine.

ive got an amp and a laptop running as a carpc so theres a couple of power cables in the boot. there is an external 2.5" hdd connected to the laptop which stores the music so the sound might be from the hdd spinning??
ive heard that you can use snap on suppressors but im not sure if they actually work.
ive tried to isolate the power cables from the audio ones but that didnt make any difference.

any ideas would be sweet cos its driving me nuts :arggg:

[jules_1972]

Turn it off?


Think there is a filter you can put in the power lead to the deck???
Sure someone will correct me..

[g0zer]

what sort of amp is it? cheap one or expensive? usually only find this with cheapy amps.

oh right, you are running a laptop.. easy to tell if the source of the noise is coming from your car or your hdd, turn off the car and see if its still there

[BennyT]

righto. its not the hdd cos its still there with the hdd unplugged

the amp is a cadence 4-channel (dunno the model number)

[xsnoiz]

Where's your earth for the amp, and are the RCA's next to the power cable?

[BennyT]

the battery is in the boot so the power cable runs directly off it as does the earth

the rca's run down the left side of the car, which is opposite from the battery so they do have a fair amount of separation

[xsnoiz]

You're running the laptop off an inverter? Where's that earthed?

[Panza83]

Also, if there is any cable running from something that is not connected it will do that.
Eg. I had a car PC, had a USB cable or something that was attached but not plugged in to anything. Whine.

[Dubs]

You messed with the BMW sound system didnt you?

They are notorious for mess ups once you fark with them

Dubs

[Dubs]

Call Rhys at Alberts in Kenwick - he may help

Dubs

[BennyT]

nah the laptop is connected directly via an cigarette lighter adapter so no need for an inverter.

all cables are plugged in.

i completely removed the bmw sound system so its not likely that its interfering.
the only things that remain from the original system is the rear speakers.

[Viper]

there is a thread on this already that may give you some things to try

[xsnoiz]

You've got a ground loop there BennyT. What that means is a voltage differential between the earth of your amp and the earth at you cigarette lighter. You'll find that your cigarette lighter is grounded to the chassis, and the amp is running straight to the battery. Measure the voltage at both earths, and you'll see what I mean. Move the amp to an earth on the chassis, and that should rectify your issue.

[BennyT]

nah cant be that cos ive got the cigarette lighter adapter plugged into a separate holder that is directly connected to the battery

ill try moving the earth tho if you think thatll help

[SIKPUPY]

Invest in a capacitor....... You will be surprised the difference it will make.

[xsnoiz]

Invest in a capacitor....... You will be surprised the difference it will make.

Yeah, right. A better battery and the big three wire upgrades will outperform a cap anyday.

[BennyT]

ive got a suppressor from a mate that im gonna try
hopefully thatll do something