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engine noise coming through amplifier


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Sad, little man 
Copper - Posts: 125
Copper spacespace
Joined: January 28, 2005
Posted: May 19, 2007 at 7:16 PM / IP Logged  
So, I just put in a new Eclipse XA2000 amp, (3122 wasn't cutting it engine noise coming through amplifier -- posted image.) and for some reason I'm gettting a little engine noise through my tweeters. But, through some testing I figured out it only happens when the line input is plugged in for each specific channel. If the left input is plugged in, the left channel does it. Right input plugged in, right channel does it.
The pins of the RCA connectors at the amp when unplugged both have resistance readings to ground in the kilo-ohm range (ie, not much of a path to ground). And the outer barrels of the connectors both have a couple of ohms of resistance to ground. Nothing seems inconsistent between the two indicating that one is shorted to the chassis or anything. I'm not really sure what the readings should be, but that's what I got. The wire is just a normal patch cable from radio shack, and I'm running it the length of the car from the HU to the amp in the trunk.
Oddly, the negative lead of the speakers on the right channel has a lower resistance to ground than the left channel. I think the left channel was in the kilo-ohm range, and the right channel was about 11 ohms. This seems weird to me, but I still think my problem is coming from the line input wire because the noise goes away with the inputs unplugged. Could it be that I just need a better shielded line input wire?
The noise also gets worse when electrical stuff is turned on in the car. From that it seems like the alternator is causing it.
Car is a '96 Mazda Miata.
'96 Mazda Miata
still_walkin 
Silver - Posts: 644
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Joined: April 18, 2007
Location: California, United States
Posted: May 26, 2007 at 12:30 AM / IP Logged  
what kind of wiring do you use?i would advise if there cheapos replace them and do you have all your wires wired on the same side. i would advise change that also i would put the power on the side the battery is and the signal and speaker wires on the other or if you what to get techincal you could put your signal in the center of the car.  sometime when your pushing alot of power you will get engine noise or alternator humming in your stereo good luck
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KarTuneMan 
Platinum - Posts: 7,056
Platinum spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member consistently provides reliable informationspace
Joined: December 14, 2004
Location: Isle Of Man
Posted: May 27, 2007 at 10:26 AM / IP Logged  
Heres a question that I was always asked when I posted about "noise"...... what kind of deck?
Sad, little man 
Copper - Posts: 125
Copper spacespace
Joined: January 28, 2005
Posted: May 27, 2007 at 1:02 PM / IP Logged  
Ok, I think I figured it out. See, the car has headrest speakers which I'm still running off of the HU because they're only little 3.5"s, and don't need to be very loud right next to your head. In order to not have to fade the head unit forward so much, I had the gain on the amp (powering the front speakers) cranked. Now, it's important to note that this doesn't mean I was cranking both my gain and my HU volume, I know all about clipping. I just had it turned up to take the place of the fader. Well, only problem is, setting the gain super sensitive means it picks up ANY engine noise as well as the true signal. My old amp didn't have this issue, but this is a class D with Eclipse's ICE power technology, so who knows what's going on inside the amp. Either way, yeah, I backed off the gain, and now any noise is down to a non-audible level. Deck is an Alpine CDA-9811.
Oh, and the routing of the power and signal wires is a non-issue. It's a Miata, the battery is in the trunk stock. The amp is hooked directly to the battery terminals (with an inline fuse on the positive wire) and the power wires are still only about a foot long. engine noise coming through amplifier -- posted image.
'96 Mazda Miata
Sad, little man 
Copper - Posts: 125
Copper spacespace
Joined: January 28, 2005
Posted: May 27, 2007 at 4:10 PM / IP Logged  
Alright, so that wasn't it. It's still there. I don't get it. I did hook up an external source to the amp. It only does it when the HU source is hooked up, so it is being induced by the inputs from the HU, not the speaker wiring or anything.
'96 Mazda Miata
tcss 
Silver - Posts: 1,623
Silver spacespace
Joined: June 07, 2004
Location: United States
Posted: May 27, 2007 at 9:01 PM / IP Logged  
Try a ground loop isolator.
There is no such thing as free installation!
Sad, little man 
Copper - Posts: 125
Copper spacespace
Joined: January 28, 2005
Posted: June 05, 2007 at 7:35 PM / IP Logged  
Ground loop isolator didn't do it. I don't even think it quieted it down at all. I would start tearing apart the car looking for the problem, but 'A' I'm not even sure what to look for, a cut in the signal wire insulation shorting it to ground? Close proximity to other electrical wires? And 'B' the signal wire has both left and right joined to each other basically the whole length of the car running under the carpeting, so if the left channel isn't doing it, how could there be a problem with how the wire is routed? Any other advice?
'96 Mazda Miata
hamzter 
Copper - Posts: 116
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Joined: March 15, 2005
Location: United States
Posted: July 16, 2007 at 7:46 AM / IP Logged  
did you get this resolved?
Mark "Hamzter" Cinense
1991 Infiniti G20 w/JDM SR20DE
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Polk DB6750
Polk DB6500
Optima Red Top in the Trunk
audiomaninc 
Copper - Posts: 108
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Joined: April 18, 2007
Location: United States
Posted: July 16, 2007 at 11:16 AM / IP Logged  
Turn off the internal amp on the deck and see what that does.  Otherwise, grab another set of RCAs and try that.  Also, if you have any other type of audio device i.e a portable mp3 player or a tone generator, plug that directly into the amplifier one input at a time, and see if the problem persists.  Good luck! engine noise coming through amplifier -- posted image.
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hamzter 
Copper - Posts: 116
Copper spaceThis member has made a donation to the12volt.com. Click here for more info.spacespace
Joined: March 15, 2005
Location: United States
Posted: July 16, 2007 at 11:25 AM / IP Logged  
audiomaninc wrote:
Turn off the internal amp on the deck and see what that does. Otherwise, grab another set of RCAs and try that. Also, if you have any other type of audio device i.e a portable mp3 player or a tone generator, plug that directly into the amplifier one input at a time, and see if the problem persists. Good luck! engine noise coming through amplifier -- posted image.
I am not sure my Eclipse CD8445 will let me turn off the internal amp.
Mark "Hamzter" Cinense
1991 Infiniti G20 w/JDM SR20DE
Eclipse CD8445
MTX Thunder 684
Polk DB6750
Polk DB6500
Optima Red Top in the Trunk
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