Noise after newly installed amp.

[NSX Swede]

Hi all.
I just installed a new aftermarket amplifier instead of the one inside the subwoofer.
I just cut all the wires from the connectors on the woofer and connected them to the amplifier (the wooferbox and the amplifier turns into one unit with the amplifier outside of the box) , but as soon as I connect the amplifier, there is a constant disturbing sound coming from all the speakers (including the door-speakers still using the original amps).
But as soon as I disconnect either the power to the amplifier or the low level signals from the stereo to the amplifier, all disturbance dissapear - the amplifier is generating the noise.
How do I filter the amplifier-noise?
Do I have to connect new powerlines from the battery to the amplifier?
Any suggestions?

 

[D'Ecosse]

It would be advisable to use seperate power & ground wires to the amplifier anyway - after-market sub amp typically requires much more current than the std. Bose component.
I suspect the primary issue is the ground - you are potentially drawing a large ammount of current through the ground wire - Fasten the ground terminal of the power input on the amplifier directly to the chassis with a good solid connection & minimum 8 gauge wire; run a fused connection wire directly from the battery positive to the amplifier + input; if there is a remote power terminal, splice a wire into the pink/white wire from the radio connector and use that to only enable the power on to the amp when the radio is on. (actually you could also use the yellow/red wire for this function which is presumably the one you were originally using for the power)
Next make a new solid ground connection directly betwen the stock head unit chassis and the car chassis.
Did you make RCA plugs for the signal connections? Make sure you have these wired correctly - the white wires should be the signal + and the oranges the grounds on the RCA cables.
That should get rid of the most serious ground loop issues - if you continue to have them, cut the black wire input to the head and connect a grounding wire directly from the same point as the previous head-chassis ground, to the head side of the cut-wire.
As a last & final solution, if any noise remains (it shouldn't at this point!) you can install ground-loop isolator between the RCA connectors and the amplifier - do a Google search & you'll find this component available at audio equipment retailers.
Good Luck!

 

[NSX Swede]

Works....

All I needed to do was to give the amp a better ground and the noise was gone.

Thanks a lot.

 

[D'Ecosse]

Glad it worked out - However, I would still recommend running a bigger gauge wire from the battery for the power & using the yellow/red one for the remote-on.
What is power rating of your amp?

 

[NSX Swede]

The Amp is marked 200W (2 channel - one for the center and one for the sub).

I checked the wiring in the service-manual, and it seems as if the power wire to the amplifier runs through a relay and a 20A fuse so it should not be any problem with the current (as long as there is not to much resistant in the wires.)

Its pretty small so it fits fine underneath the glovebox without interfear with the feets of the passenger.
Works fine although it would be great to have a little more volume on the centerspeaker....