OK! So this article is going to explain a little bit about amp install and how to avoid that terrible alternator noise.
(On a plus note, newbs in your car often think you have a turbo. let them think that)
I’m using 2 amps and have been plagued with this problem on and off for a while now. I decided enough was enough and went to go talk to some upper year peers here at western that are in power supply design and now I can pass on some info to you guys.
OK so let’s assume you have the same problem as me. There is a whining coming out over your speakers that changes pitch with RPM. Very common, very annoying. This will not be heard through your sub channel especially if it is x-over’d properly because of its high frequency.
First try and relocate your RCA wires away from other wires, and if they cross other wires try to do it at 90 degrees. Try using higher quality shielded RCA cables. If none of this resolves the problem it is likely a grounding issue.
I’ve always been told not to ground my amps together to prevent one amp from grounding through the other. This is bad advice and not really true.
Here’s the truth:
To prevent power ground loops from being introduced into the signal the amps and headunits must all see the same reference ground. In theory any point on the car should be the same ground but in our older cars this is no longer the case. Different spots will have different resistances to the negative battery terminal. Especially if you only have one set of preouts and you need to pass the RCAs through one of the amps … having them see different grounds will mean you will definitely get a noise problem. Higher quality components will be more immune to this …
So … your headunit and amps should all see the same ground. But oh nos! Doesn’t that mean the more powerful amp will start to ground through the headunit and smaller amp(s) ? Only if you’re a chump and didn’t find a ground with a low enough resistance to the battery.
So my suggestion? Run wiring (same gauge as the power supply obviously) from all the amps and the headunit to one central location and connect them all. Then run even larger gauge wiring to a couple different ground points (the electrons will optimize themselves to ground best … give them a couple options just so you don’t have to touch this stuff ever again).
Voila … your amps and headunit will see the same reference ground and it will prevent ground loops. Nothing will ground through anything else if you found at least one good ground.
Questions / comments / disagrements / other suggestions ?
Post!
