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VTJC
08-16-2006, 10:59 PM
A little while ago I upgraded the stereo in my MC. A new Alpine head unit, amp, 4 speakers and left the Infinity powered sub in place. We connect the amps to the head unit with RCA’s. When the engine is off it sounds great. However when the engine is running we get a whine in the stereo that gets worse with increased RPM. Any thoughts on a cause/remedy? Stereo shop thought it could be negative/ground connection to amp or suggest filters for RCA’s(but they are $20 each and we need 3).

Should my 99 have a shielded alternator?

Thanks in advance for advice.

kennbarbie
08-16-2006, 11:42 PM
First dissconect the powered sub and see if the whine goes away. If not go down to your local electronics store and pick up a "Ground Loop Isolator". This will hook up to your head unit with both inline on your power and ground wires. They are very easy to hook up.
Finnally if that dosn't work, change your spark plugs. Ya-ya, some of you are thinking what am I smoking, but trust me, it works. Change them to a different company then what you are useing now. It works.
If those dont work, PM me and I can give you a few more suggestions on what to try, ie: are you using good cables, size of wire, and grounding points. Good luck

VTJC
08-16-2006, 11:50 PM
Thanks after I do some test this weekend I will let you know how it goes.Good quality wire and cables. Sub, amp are connected directly to battery after going through fuse panels.

Leroy
08-17-2006, 12:03 AM
Alternator problem is likely, wiring is another possible culprit, but it may be simpler to go to Radio Shack and pick up something like a ~0.1uF capacitor. Get non-polarized, >50 volts and then you can try it at several locations. When you find the problem, mount it there.

SKI*MC
08-17-2006, 12:08 AM
I think my car does this, but i can only hear it when my stereo is tunred down (not all the way though) I may just be stupid, and its coming out of my engine.. i don't think so though. But i am not running an amp or sub yet..

VTJC
08-29-2006, 10:48 PM
Disconnecting the powered Sub, made no change, the powered sub actually was installed before the new head unit, amp and speakers. I have good quality components, wire and RCA’s. Everything is grounded directly to the battery. I will try Ground Loop Isolator next. Jamie

JimN
08-29-2006, 11:26 PM
Alternator whine can be caused by a stressed bridge or grounding issues. If there's a ground loop, the ground loop isolator may get rid of the noise but in some cases, the bass response goes to #%#$& in a handbasket. Better to actually fix the problem that put a band aid on it. Measure the resistance from the battery negative post to the head unit's case, then from the same post to the powered sub's negative lead, where it connectc to the ground wire. If there's more than .1 ohm difference, there's a ground loop. Long ground wire runs are like as antenna and will pick up whatever noise is available. The best way to wire the system is to run a power positive and negative wire to an area close to any equipment and connect everything to them. If possible, twist the pos and neg wires along the way and separate them about a foot from the ends. This is a really cheap and easy way to reject noise since any noise in one cable will be canceled by the noise of opposite amplitude in the other cable.

If the audio cables go past a noise source, like the wiring under the dash, it's very possible to pick up the noise there. Cheap cables hurt more than they help but Monster Cable isn't necessary (I and a lot of other people in the audio business hate them because they're a prime example of marketing selling something that isn't really better than most other similar products). Twisted pair audio cables are far better and Stinger is one brand that sells these. Another easy way to inject noise is by bundling the audio cables with the power cables or run them in a way thay they're parallel. If the audio cables need to pass the power, they need to go at a right angle to keep the noise level down.

The second thing I would try, after cleaning the battery posts and clamps, is the resistance test. Next, try attaching a wire from the audio cable ground to the case of the head unit. If the noise goes away, solder a wire to one of the audio grounds and attach the other end to the case of the radio.