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Alrighty guys, so here's a wierd problem. I ONLY get alternator noise (in relation to engine RPM) if the stereo is OFF. Only if it's off....I know wierd right? It gets wierder. If I turn on the radio, even at ZERO volume, the noise stops. But if I turn it off, it's right there again....so this leads me to believe that the noise is not being amplified and is somehow only added in when the head unit is off. So here's a couple of things though that may make things easier (or more difficult) to pin point the problem.

1) I used a 0/1 gauge kit with the power down the drivers side and the RCAs, remote turn on wire, and antenna wire on the passenger's side.

2) I beefed up the battery terminals with clamps that have a 0gauge, 4 gauge and (2) 8 gauge ports.

3) The ground connections are super clean. I used a rotary steel wire paint stripper in a cordless screwdriver to clean the grounds off.

4) The head unit is an old POS Sony CDX1300 (it was free) that only has Rear channel line outs. The speakers are wired in parallel at 2 ohms on each side to the 1/2 channels fed by the rear line outs (that's changing pronto).

5) Also, the head unit does not have a remote amp turn on lead. Only a power antenna lead, so the remote lead is connected to the ACC circuit.

5) The amp is an Audiobahn A6004T ([email protected] x 4 or [email protected] x 2 or [email protected] x 2 (bridged)).
Common Features
Class A/B MOSFET Circuitry
PWM MOSFET Power Supply
double-sided Glass Epoxy Circuit Board
THD: 0.02%
S/N Ratio: >100dB
Frequency Response: 10Hz - 40KHz (+/- 1dB)
Variable 18dB Hi-pass Crossover: 50Hz - 750Hz
Variable 18dB Low-pass Crossover: 50Hz - 120Hz
Bass boost on / off
Subsonic Filter: 20Hz - 50Hz
RCA Throughput Connections
3-way Protection Circuitry: Thermal, Short Circuit and Overload
Cooling Fan
Cobalt Blue Illumination
High Gloss Chrome-Plated Finish
Air Induction Fan Cooled
RCA and Speaker Level Inputs
Nickel-Plated Block Terminals

So what do you guys think?

-mobiuslogic

PS. Don't mean to sound like a butt, but I'm not asking for any opinions on equipment choices. As far as I've seen, many on the boards think Audiobahn sucks or is just for show. Well, considering my door panels bulge almost 1" out and I've had to clean out every bit of change and loose items anywhere while it still sounding crystal clear (even with the crudy Sony), I have to say and damn pleased. But you can talk all the smack about the Sony you want. I'm fed up with that thing. :lol2:
 

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If the noise is only happening when the stereo is off, it sounds like it would be injecting into the speaker wire to me. Is the noise coming from all the speakers? What did you use for speaker wires and where did you run them?
 

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Discussion Starter #3
I used my Metra kit wiring harness that *would* be run from the head unit to the stock harness in the trunk so the power from the head unit would go to the stock wiring and speakers. I routed the harness through the rear of the trunk to the passenger's side and it comes out next to the amp. Any idea?

-mobiuslogic
 

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So, if I'm reading this right, this is how the signal travels: headunit > RCA's > amp > wiring harness > RCU > stock speaker wires.
I have an idea of what the problem could be. Does the amp stay on even when you turn the headunit off? If you haven't checked, you should. If the amp is on, then it's amplifying whatever signal it receives through the RCA's and sends that signal to the speakers. When the headunit is on, it transmits a signal to the amp, even when the volume is turned down. If the headunit is off but the amp is still on, it will amplify alternator whine and suspension noise because those sounds invade the RCA's.
If the amp is on when the headunit isn't, put a toggle switch somewhere in your turn-on line so you can turn off the amp. Check that out and let me know if it worked.
 

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Discussion Starter #5
So, if I'm reading this right, this is how the signal travels: headunit > RCA's > amp > wiring harness > RCU > stock speaker wires.
Very Close. But the RCU is cut out. There are really 2 wiring harnesses. 1 from the RCU->Speakers (RCU Harness) and the other one is designed to bypass the RCU and plugs the Head Unit directly into the RCU harness through a matching connector, the other end of it is just 9 wires (4 pairs of +/- speakers and 1 power antenna). So it goes: headunit > RCA's > amp > wiring harness > stock speaker wires.

Does the amp stay on even when you turn the headunit off?
Yes. Because my head unit doesn't have an amp turn on wire I had to wire it to the ACC wire that powers the head unit; so yes, any time the ACC circuit is live (ie: car is on) the amp is on, even if the head unit is off.

So that would make sense. The amp is on all the time, even if the head unit is off, so it's just amplifing ground and alternator noise. Why "suspension" noise though? That didn't make a whole lot of sense. Everything else did though.
Thanks buddy. I'll wire a switch on it pronto style.

-mobiuslogic
 
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If you were to remove the RCAs out. Would the sound go away? I dont like the idea of the RCAs and Power wire in the same area... I know lots of times you can get away with running the wires this way. But sometimes you get that TYPE of wire that wants to be a ****..lol



Sal
 

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If the power wires and RCAs are run in the same area, and there's enough current running through the power, you'll get problems. I only have 8 gauge in my car, but I'm sure that 0/1 gauge will cause some noise problems. That's a TON of current running through there.

JR
 

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Start unplugging things until it goes away...if you can't isolate it or control it this way, try buying a ground loop isolator.
I only have 8 gauge in my car, but I'm sure that 0/1 gauge will cause some noise problems. That's a TON of current running through there.
Wire diameter, has to my knowledge, no relation to inductance. It's mostly a function of current, direction, and the distance between the conductors.
 

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Originally posted by mobiuslogic@Sep 7 2004, 02:29 AM
Why "suspension" noise though?
I don't know if you would pick up suspension noise in our cars, but my buddy has a Grand Cherokee, and he had the same problem you do, with no turn-on wire on the CD player. His amp was only for a sub, and everytime the radio was off but the amp was on, he'd hit a bump in the road and the sub would pound. I don't know if just the speakers would do anything that dramatic, but I've heard it happen. We solved his problem with a toggle switch too. Glad I could help, I know how frustrating it is :)

If the power wires and RCAs are run in the same area, and there's enough current running through the power, you'll get problems.
Guys, if you read his first post, you'll see that he has the power wire down the driver's side and everything else down the passenger side.
 
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