How to suppress engine noise from a stereo amp installed onto my Harley davidson?

[Vivkins3]

I installed a stereo amplifier to play my sat nav through on my Harley. It works fine except that I get a humming that increases with the engine speed. This happens even when I have the sat nav turned off which eliminates any interferance to that so it must be the amp that is picking it up. Does any one know how to eliminate this noise please.

[Graham-W]

Could be noise from your alternator getting into your amps power supply. What you need is a ground loop isolator in your power supply line to the amp.
Something like this may work: http://www.ebay.co.uk...60721174538%26ps%3D54

[Hymie]

The noise is either radio frequency interference (from the ignition system on the bike), or caused by a fluctuation (noise) in the DC supply voltage (to the amp) from the bike’s magneto/generator.

First you need to determine which it is in order to eliminate the noise. Hook up the amp with a DC supply voltage separate from the bike’s generator; if there is no noise – then it is due to a poor bike DC supply voltage, otherwise it is rf interference.

The fix for a poor bike DC supply voltage is to apply smoothing to the supply, rf interference is a bit more tricky to suppress.

[Vivkins3]

Thanks Graham I'll get one. Cheers mate.

[Hymie]

If Graham-W’s fix does not work – you could try this.

http://www.ebay.co.uk...y&hash=item3f0b43cfe8

This item smooths (removes noise from) the DC supply – whereas the former item only treats/modifies the audio signal.

If you still have a problem after fitting both – buy a new amp.

[beso]

Graham-W //What you need is a ground loop isolator in your power supply line to the amp. //

Ground loop isolators don't go into the power supply line but the signal line.

Basically they are a transformer and capacitor coupled circuit that DC isolates the signal ground of the source and amplifier. This prevents a loop that forms through the signal ground and the power supply ground.

The ground loop act as an antenna picking up electromagnetic interference and causing a small current to flow in the loop. This current causes a voltage drop in the signal ground between the two devices and that is then amplified.

Ground loops are rarely a problem in closely spaced devices. If the grounding is done correctly with the ground of both devices having a single ground connected to a common point then it can't happen. The loop isolator is quite unnecessary unless it is impossible to mount the two devices with a common ground point.

If proper grounding does not fix it then Hymie's noise suppressor is a potential solution. The usually consist of a choke and one or two capacitors that removed the ripple from the power supply.

The currents running in the ignition system can cause interference. Connect a capacitor between the battery side of the coil and ground.

Avoid connecting the amp power anywhere in the circuits that feed the ignition system. This can be difficult since the ignition switch is usually part of the amp power circuit. Try connecting the amp directly to the battery and see if that makes a difference. If so then you could use a relay to switch the power to the amp and control it from the ignition. (Be sure to fuse protect this connection.)

Another place the noise can come from is directly from the ignition leads. These currents can induce noise into the circuits connected to the equipment. Keep all wiring as far away as possible from the ignition system and try to get grounded metal between the sound system leads and the ignition.