engine noise coming through amplifier
Printed From: the12volt.comForum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=94064
Printed Date: April 19, 2024 at 12:46 AM
Topic: engine noise coming through amplifier
Posted By: Sad, little man
Subject: engine noise coming through amplifier
Date Posted: May 19, 2007 at 7:16 PM
So, I just put in a new Eclipse XA2000 amp, (3122 wasn't cutting it 
) 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.
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'96 Mazda Miata
) 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.
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'96 Mazda Miata
Replies:
Posted By: still_walkin
Date Posted: May 26, 2007 at 12:30 AM
Posted By: KarTuneMan
Date Posted: May 27, 2007 at 10:26 AM
Posted By: Sad, little man
Date Posted: May 27, 2007 at 1:02 PM
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.
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'96 Mazda Miata
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.
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'96 Mazda Miata
Posted By: Sad, little man
Date Posted: May 27, 2007 at 4:10 PM
Posted By: tcss
Date Posted: May 27, 2007 at 9:01 PM
Posted By: Sad, little man
Date Posted: June 05, 2007 at 7:35 PM
Posted By: hamzter
Date Posted: July 16, 2007 at 7:46 AM
Posted By: audiomaninc
Date Posted: July 16, 2007 at 11:16 AM
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! 
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2003 Dodge Neon R/T
Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4
140.7 @ 28Hz
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2003 Dodge Neon R/T
Alpine CDA9813, RF T2000.1bd, RF T162S, RFT142C, RF T600.4, RF T215D4
140.7 @ 28Hz
Posted By: hamzter
Date Posted: July 16, 2007 at 11:25 AM
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!
I am not sure my Eclipse CD8445 will let me turn off the internal amp.
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Mark "Hamzter" Cinense
1991 Infiniti G20 w/JDM SR20DE
Eclipse CD8445
MTX Thunder 684
Polk DB6750
Polk DB6500
Optima Red Top in the Trunk
Posted By: audiomaninc
Date Posted: July 16, 2007 at 12:25 PM
Posted By: kungwaz
Date Posted: July 18, 2007 at 7:16 AM
Posted By: hamzter
Date Posted: July 18, 2007 at 9:06 AM
Posted By: chaos420
Date Posted: July 18, 2007 at 9:53 PM
Posted By: forbidden
Date Posted: July 18, 2007 at 10:35 PM