Altornator whine / noise - diyAudio
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Old 24th September 2012, 01:16 PM   #1
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Default Altornator whine / noise

Hello.. Long time visitor to the site but this is my first post.

I just did full audio upgrade to my girlfriends new car and have a case of alternator noise coming in through the front components.

Amp is a Kicker ZX700.5 2010 or 2011 model. Components are Image Dynamics ctx-6.5cs. I have the amp bridged from 4 channels to 2 (and a single channel for the sub).

Now to the noise.. it varies with the engine speed, goes away when I disconnect the front RCA inputs from the amp. If I plug my phone into the amp RCA inputs I can play audio to the speakers with NO engine noise.. So I think the amp and speaker wires are ok.

I have tried:
new RCAs
routing the HU ground to the amp
routing the HU ground to the battery
routing the amp ground to the battery
doing a shield fix on the RCA cables (to ground them to the case of the HU)
unplugging the radio antenna

None of those have worked..

Things I still need to try:
Big 3 upgrade (ordering 0/1 gauge terminals today..)
Adding a capacitor (I have mixed feelings about this possibly working)
Testing a different amp ( I would need to buy one)

Any other tips or ideas? I have checked some other posts related to this issue and tried to do a RCA shield fix on the head unit.. From the RCA shield to the HU case I was getting 3 ohms, so I grounded them like I was told and now it reads 0.9 ohm but I still have the noise.
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Old 24th September 2012, 03:28 PM   #2
maylar is offline maylar  United States
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Invariably, alternator whine is due to a difference in ground potential between the source and amp. Your amp has differential inputs according to the manual, which makes this problem strange - usually such amps are immune.

Seems like you've addressed all the things most people would suggest. Relocating either the HU ground or amp ground is usually the solution. I have an extreme case with a Pioneer HU (notorious for bad RCA ground) in a car where the HU is mounted to metal and the ground is not in my control. The only solution I could find was a ground loop isolator.
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Old 24th September 2012, 03:58 PM   #3
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Quote:
Originally Posted by maylar View Post
Invariably, alternator whine is due to a difference in ground potential between the source and amp. Your amp has differential inputs according to the manual, which makes this problem strange - usually such amps are immune.

Seems like you've addressed all the things most people would suggest. Relocating either the HU ground or amp ground is usually the solution. I have an extreme case with a Pioneer HU (notorious for bad RCA ground) in a car where the HU is mounted to metal and the ground is not in my control. The only solution I could find was a ground loop isolator.
I have read about RCA mute plugs.. I might give that a shot to see if it is the amp (although I dont think it is..)

Does a ground loop isolator have any drawbacks? do you lose sound quality?
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Old 24th September 2012, 05:27 PM   #4
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Some people claim that they can hear a difference with a ground loop isolator but I think it depends on a lot of variables so you'd have to try it to see if it works well for you and your system.

How bad is the noise?

With no RCAs connected to the amp and the amp off, do you read anything less than 100 ohms between the amp ground and any of the individual speaker terminals?

If you disconnect all of the speakers from the amp and use a test speaker with a short length of wire, do you get engine noise on any of the 5 channels (head unit plugged into the amp)?
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Old 24th September 2012, 05:31 PM   #5
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Please disconnect the negative supply to your head unit , your problem should be sorted , provided you are not using the head units - chip amps to power front speakers or the like .

Suranjan
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Old 24th September 2012, 06:43 PM   #6
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Originally Posted by Perry Babin View Post
How bad is the noise?

With no RCAs connected to the amp and the amp off, do you read anything less than 100 ohms between the amp ground and any of the individual speaker terminals?

If you disconnect all of the speakers from the amp and use a test speaker with a short length of wire, do you get engine noise on any of the 5 channels (head unit plugged into the amp)?
I can hear it if the volume is low or on mute.. if I am listening to it at medium to max volume I can not hear the noise most of the time.

I will test out the two things you listed there after work today.. thanks for the assistance.

Quote:
Originally Posted by hunter audio View Post
Please disconnect the negative supply to your head unit , your problem should be sorted , provided you are not using the head units - chip amps to power front speakers or the like .

Suranjan
So If I just disconnect the ground to the HU all together that would fix my problem? I do not have any speakers being powered by the HU, only front components and a sub being powered by the external amp.

By "negative supply" do you mean the ground wire?
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Old 24th September 2012, 07:20 PM   #7
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Setting the gain a bit lower may be enough if the noise isn't loud.
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Old 24th September 2012, 07:43 PM   #8
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Originally Posted by Perry Babin View Post
Setting the gain a bit lower may be enough if the noise isn't loud.
I will give this a shot also
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Old 24th September 2012, 09:13 PM   #9
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Have you tried to move the rca cables around to try and find a quiet spot?
My alpine HU with zapco line drivers and balanced cable was picking up noise and I found that the short rca's that plug into the back of the deck from the line drivers were picking up noise from the wire harness behind the deck. Had to pull the deck, start the car and with the stereo on, find a home for these wires that did not pick up noise. You will want to do this as it drive me nuts to hear noise in the audio.
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Old 25th September 2012, 12:37 PM   #10
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Originally Posted by 90scaraudio View Post
Have you tried to move the rca cables around to try and find a quiet spot?
My alpine HU with zapco line drivers and balanced cable was picking up noise and I found that the short rca's that plug into the back of the deck from the line drivers were picking up noise from the wire harness behind the deck. Had to pull the deck, start the car and with the stereo on, find a home for these wires that did not pick up noise. You will want to do this as it drive me nuts to hear noise in the audio.
Hmm I will look into this also.. I had a set of RCAs running outside of the car to the amp to test the RCAs but I dont know if I made sure to keep it away from a harness.. Ill give this a shot.
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