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Discussion Starter · #1 ·
Hey guys I recently installed a new Alpine 400W amp, JL Subwoofer, and 2 Boston Acoustics for the doors (RT/10). The sound is really good, but I get this engine whine when the car is on.

Now I'm aware of some ground looping problems and other electrical issues, but this is drivin me nuts... can't pin point it. /images/graemlins/freak

I'm using the stock Alpine head unit, which worked fine/no noise w/ the stock Viper's amp. I spliced the output wires from the HU to fit the input plug on the Alpine amp. The same for power/ground.

Some points:
The engine whine is only present when the car is on (duh)
The engine whine does not get louder with the stereo volume!!!
It does go up and down with the engine, so its prolly alternator noise
The gain on the amp is not past middle
When I unplug the HU inputs to the amp while the car is on, the noise is gone

This tells me the noise is being introduced somewhere between the HU and the amp (but prolly not in the HU itself). I took the wires, and did some temp insulation for EMI tests.. I wrapped the shielded HU wires in aluminum foil... didn't effect it at all.

The HU wires are really thin (factory wires). They were wrapped from the factory in shielding, which I have going to the ground lead on the amp (common). One other weird thing.. the HU has four outputs: front left, right; rear left, right. Front and rear left channels both share the same ground path, and the same for Front and rear right. I thought most HU's have a diff ground path for each of the four channels?
 

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Most likely the alternator.
 

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Discussion Starter · #3 ·
Yep, I think it is the alternator. Any idea what the solution is? Wonder if I can throw a condenser in somewhere.
 

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What plug wires are you using?

If you are using an aftermarket wire like MSD or the like, that could be your problem right there.

Other than that it sounds like a poor ground.

Just mt :twocents:
 

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Discussion Starter · #7 ·
I'll keep ya posted. I'm gonna try some of this stuff tomorrow. I still have the stock plugs and cables, so I dont think its them.

I was kinda thinking I'll need a better ground so I'll try that first...

A line isolator does seem like the easy way out so I'll look around for one.

Thanks for the help /images/graemlins/nana
 

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GoddFadda said:
A line isolator does seem like the easy way out so I'll look around for one.

Thanks for the help /images/graemlins/nana

Radio Shack...$15 each...You probably need two...worked for me.
 

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Discussion Starter · #9 ·
Sold! Call me lazy, but thats a helluva lot easier than messing around w/ a ground wire!!
 

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Discussion Starter · #10 ·
Well, got it figured out...

The problem? The short between my keyboard and my chair.

I'm a schmuck and had the HU's outputs wiring to the speaker level inputs of the amp. As soon as I soldered on some RCA jacks to those HU outputs and put em into the line level input of the amp... whine is gone. Crystal clear sound.

:dumbass:
 

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So they probably grounded one of the speaker lines in the amp in an attempt to reduce the signal strenght before sending the signal further into the amp.

The number one reason for signal noise is cheap amp manufacturers who join signal ground with power ground. When i used to work as a sound engineer in the 80's (that's what payed my way through college) i had to get inside so many amps to remove crossed signal grounds from power grounds.

Good to hear you got it solved.
 

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I'm so glad it was that easy for you. I had the same problem a few weeks back when I put a new fosgate amp and kenwood headunit in. It drove me NUTS! I was told by many audio shops that I had to run the RCA wires and power wires on complete opposite sides of the car. So I had to tear my car apart and drill holes and run them into the trunk. Still to no avail. Ended up being the head unit not having a strong enough pre-out. It was only 1.5 so I stepped up to the Kenwood excelon which had a pre out of 3.5 and it solved the problem. What hell I went though though in a 3 week period. I went with the Alpine R's in the doors with an MTX 404 amp and it kicks ass. Not enough bass though so I will be installing bass shakers under the seats this week. The lack of room for subs has to be my only dissappointment with this car for me. If I don't like it then I will be losing the spare tire and putting a 15"sub in the trunk.
 
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