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Discussion Starter #1
Hello all. Dealing with a little bit of an alternator whine issue on my 2007 Porsche Cayman. I'm running a Sony xav-ax5000 head unit rca out to a Zapco DSP Z8 which feeds a JL Audio XD800/8. I'm getting a persistent alternator whine due most likely to the fact that the RCAs between head unit and DSP must pass very close to the main charging cable for the battery. I've upgraded the RCA cables to shielded ones, checked grounds, reduced amplifier gain as much as possible, etc, but it's not cooperating so far.

Any ideas on how to best deal with this? A balanced line driver crossed my mind, but I don't know what options are out there these days.
 

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In my experience, routing RCAs close to power wires rarely causes noise. I'd take a closer look at your grounds. You have a DSP, an amp, and a head unit, are they all grounded to the same spot, or different spots?
 

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I agree with gijoe. These issues are normally groud related. Have you tried rerouting the RCAs or the power on a temp basis to confirm the noise is due to due proximity?
 

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Tying in all your grounds to one common location will reduce the chance of difference in voltage potential which is generally the cause of noise.

Also try noise in these scenarios 1) ACC 2) Key Forward Car OFF 3) Car running

Some car's can produce noise at 2).

Other sources of noise can be dealing with balanced / unbalanced systems.
 

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Discussion Starter #6
In my experience, routing RCAs close to power wires rarely causes noise. I'd take a closer look at your grounds. You have a DSP, an amp, and a head unit, are they all grounded to the same spot, or different spots?
I started from a presumption that it was ground related as well, but have not had success pursuing that option. Currently amp and DSP are grounded together, with head unit grounded to factory wire. I did try bringing ground from the amp/dsp point to the head unit with no success, didn't bother routing wire through dash after that as it is a pain in the ass due to the car's size and low stance. Ohmmeter shows near 0 resistance between the two ground points, but that obviously isn't completely reliable.

I agree with gijoe. These issues are normally ground related. Have you tried rerouting the RCAs or the power on a temp basis to confirm the noise is due to due proximity?
I did run a long RCA out and around, and whine levels varied depending on how close you got to the battery area. Never could completely eliminate them though that method, which I attributed to the fact that my extra long RCAs were completely unshielded cheapo home variety that I had sitting around and not quite long enough to go completely out and around.

Have you unplugged the RCAs from the DSP inputs to see if the noise persists?
Noise is eliminated if you unplug source RCAs from the DSP inputs.

I should also note that originally the system used a Nexus 7 tablet as a source with a USB to Optical DAC that fed the DSP via Toslink cable. Never had any noise issues with that setup at all. Only surfaced when I switched to the Sony. Had backup cam and charging issues with the Nexus, so I ditched it.
 

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Noise is eliminated if you unplug source RCAs from the DSP inputs.
This tells me that you should try grounding the head unit to where the amps/dsp are grounded. You mentioned you tried similar though? It was worded in a way that is hard to follow if you did exactly what i suggested or something different.
 

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Discussion Starter #8
This tells me that you should try grounding the head unit to where the amps/dsp are grounded. You mentioned you tried similar though? It was worded in a way that is hard to follow if you did exactly what i suggested or something different.
I used a length of 12 Gauge wire, roughly equal to factory head unit ground dimensions, and went from head unit to the negative battery terminal, where the amplifier and DSP were already grounded. As getting through the firewall is a pain in the ass due to the small dimesnions of the footwell in the car, I simply went out the door and around as a test of theory before doing the work. This did not yield any change in behavior, so I did not bother with running a new wire from headunit to battery negative terminal.
 

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Probably not the best method and I know people are going to hate me for this but look into a ground loop isolator.

Specifically a Jensen CI-2RR Iso-Max. It's expensive but after months of troubleshooting my alt. whine issue, I said to hell with it and purchased the Jensen Transformer.

Never looked back since.

You can purchase through Part Express. If it doesn't work, I know they have an excellent return policy.

https://www.parts-express.com/jensen-iso-max-ci-2rr-rca-stereo-line-input-isolator-hum-eliminator--246-0116?utm_source=google&utm_medium=cpc&utm_campaign=pla&gclid=CjwKCAjw27jnBRBuEiwAdjQXDAPHztdcEIh5dXcQYlCsTBWY-6Gdc-p4H1-TTh6EMoUKH1Ll5PmmBxoCm_cQAvD_BwE
 

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Back in the day we used to ground the outer RCA sleeve to the back of the radio itself. Just take a short piece of black primary wire, put a ring terminal on the end and screw it to the backstrap hole on the back of the radio. Then strip the other end and trim back a few of the wires and bend it over. Loop that over the outside of the RCA sleeve and reconnect it. If that doesn't help, try to do the same thing on the other end, short piece of primary wire, ground it to the amp ground, and bend over the other end around the outer RCA sleeve. If that doesn't work, disconnect ground up front and try it with just rear RCA outer grounded.

Also anywhere your RCA crosses a power wire, if possible do it at a right angle to minimize the noise.
 

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If your system is running 100 amps or more you should consider running a dedicated ground from body ground at battery to rear block to feed amps / dsp.

Is radio still grounded through factory ground wire?
 

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Discussion Starter #12
Back in the day we used to ground the outer RCA sleeve to the back of the radio itself. Just take a short piece of black primary wire, put a ring terminal on the end and screw it to the backstrap hole on the back of the radio. Then strip the other end and trim back a few of the wires and bend it over. Loop that over the outside of the RCA sleeve and reconnect it. If that doesn't help, try to do the same thing on the other end, short piece of primary wire, ground it to the amp ground, and bend over the other end around the outer RCA sleeve. If that doesn't work, disconnect ground up front and try it with just rear RCA outer grounded.

Also anywhere your RCA crosses a power wire, if possible do it at a right angle to minimize the noise.
They used to actually make RCA wires with an integrated ground for this purpose, but I haven't seen them in my search so far. I do have the RCA crossing the path of the positive lead at a right angle, and as far away as is physically possible in the confined area, which would be about 4 inches.


If your system is running 100 amps or more you should consider running a dedicated ground from body ground at battery to rear block to feed amps / dsp.

Is radio still grounded through factory ground wire?
There is already a dedicated ground. The amp sits less than 2 feet from the battery, so it is grounded directly to the negative Battery Terminal with 4 guage wire. The JL uses an 80 Watt fuse anyway. The Head unit is still grounded to the factory ground at the moment, but as mentioned above, running a dedicated ground did not affect the noise.
 

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In my experience, routing RCAs close to power wires rarely causes noise. I'd take a closer look at your grounds. You have a DSP, an amp, and a head unit, are they all grounded to the same spot, or different spots?
Your experience is understandable...

The reason is that most of the power wires are carrying steady current.
And the magnetic field is not changing.

If you run them beside a CAN buss, or some lines where there is alternating current (or some pulsed current draw), then the magnetic felid will be changing and the RCAs will act like 1/2 of a transformer shielded or not.
 

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Your experience is understandable...

The reason is that most of the power wires are carrying steady current.
And the magnetic field is not changing.

If you run them beside a CAN buss, or some lines where there is alternating current (or some pulsed current draw), then the magnetic felid will be changing and the RCAs will act like 1/2 of a transformer shielded or not.
Right. Running them close to something like a fuel pump can cause some trouble, but I've never had an issue with noise from power wires.
 

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Try powering your head unit with a different power source/wire. Unplug your factory antenna. Sometimes the factory HU grounds through the antenna and can cause problems with aftermarket radio's.
 

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I like this train of thought. If your factory ground is not that great your antenna ground becomes the path of least resistance.

Also consider this, if you were to try a ground loop isolator, you actually have 2 sources of input for turning on your radio, your constant power and your accessory power. As a test I would actually twist power / acc and hook up to to GLI and see for hell of it if it makes a difference. If it was enough to deter your whine then I would try 2 GLI's, one on power, one on constant.
 

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Right. Running them close to something like a fuel pump can cause some trouble, but I've never had an issue with noise from power wires.
That fuel pump example would need a lot of pulsing current.

However you've nailed it with the grounds... most ground loop problems have a problems with multiple grounds, and big open loops.
(Fixing the alternator, does not fix the ground loop.)
 

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I had great results with a $12 noise filter (PAC CSS-12).

https://amzn.to/2MmgKDc
I have used something like this before with success as well,
seems like grounds should have resolved it but in the end this for the head unit, was nice to have that noise gone
 
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