Amplifier Interference

MOB · 08-13-2008, 06:58 AM

I've added a Blaupunkt plug n play THA555 amp to my E92 as per some instructions on here - sounds great, but I have a really annoying interference problem.

When I press the start engine button, there is a whizzing noise from the speakers. If I then press the accelerator, the whizzing noise rises in pitch matching the engine revs

The amp inputs come straight from the existing BMW wiring behind the head unit using a vehicle specific adapter, and the amp is connected to the positive and negative terminals of the battery.

Anyone any ideas how to get rid of this?

- perhaps earth the amp to the body of the car instead of the battery?
- the amp input cables run down the centre of the car, tucked under the centre console trim - could there be something there interfering?
- any other ideas?

I plan to tackle it tonight but just wondered if anyone had any tips/experiences/ideas.

tpipta · 08-13-2008, 08:17 AM

Absolutely, get rid of the long ground cable and run a ground to the vehicle chassis that is only a couple feet away. That in it of itself could fix your problem. Also, if you have the power, ground and hi/low (frequency) audio cables running next to one another, you could also be inducing a noise on that front as well!

Good luck!!

Best,

Tony

tintivilus · 08-13-2008, 12:10 PM

If shortening your ground lead doesn't help, you could also try using chokes on the power and/or ground wires.

Usually this is caused by long runs of signal cables next to power cables, poorly shielded signal cables, or shorts between signal ground and chassis ground (ie metal connector shell shorted to body). Last time I had an issue like this it was resolved by heat-shrinking the (metal) RCA signal plugs.

08-13-2008, 06:58 AM	#1
MOB Major 57 Rep 1,413 Posts Drives: Alpine White M2 LCI Join Date: Dec 2007 Location: Northants UK iTrader: (4)	Amplifier Interference I've added a Blaupunkt plug n play THA555 amp to my E92 as per some instructions on here - sounds great, but I have a really annoying interference problem. When I press the start engine button, there is a whizzing noise from the speakers. If I then press the accelerator, the whizzing noise rises in pitch matching the engine revs The amp inputs come straight from the existing BMW wiring behind the head unit using a vehicle specific adapter, and the amp is connected to the positive and negative terminals of the battery. Anyone any ideas how to get rid of this? - perhaps earth the amp to the body of the car instead of the battery? - the amp input cables run down the centre of the car, tucked under the centre console trim - could there be something there interfering? - any other ideas? I plan to tackle it tonight but just wondered if anyone had any tips/experiences/ideas.
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08-13-2008, 08:17 AM	#2
tpipta First Lieutenant 24 Rep 318 Posts Drives: F15 X5 Join Date: Apr 2008 Location: Annapolis, MD iTrader: (0)	Absolutely, get rid of the long ground cable and run a ground to the vehicle chassis that is only a couple feet away. That in it of itself could fix your problem. Also, if you have the power, ground and hi/low (frequency) audio cables running next to one another, you could also be inducing a noise on that front as well! Good luck!! Best, Tony
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08-13-2008, 12:10 PM	#3
tintivilus Lieutenant Colonel 26 Rep 1,826 Posts Drives: E92 335i Join Date: Sep 2006 Location: Lake County, IL iTrader: (0) Garage List 2007 E92 335i [0.00] 2003 325i [0.00]	If shortening your ground lead doesn't help, you could also try using chokes on the power and/or ground wires. Usually this is caused by long runs of signal cables next to power cables, poorly shielded signal cables, or shorts between signal ground and chassis ground (ie metal connector shell shorted to body). Last time I had an issue like this it was resolved by heat-shrinking the (metal) RCA signal plugs.
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