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Old 04-22-2013, 07:16 AM   #1
Jimfred
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Per amp output noise

I have installed a pioneer HU,Rockford p-44-2,Rockford p-55-2,JL components front and rear and 2 Rockford 12" subs in custom box,I have 3 pair of RCA cables running on left side rocker 1 pair is twisted to the subs other 2 pair are new that came with amp kit I also ran the aux wire and an extra ground wire that I tied from HU to amp grounds,I can't get rid of humming noise when volume is all the way down and car is running.yesterday after taking car apart again I took extra RCAs I had and ran them from back of HU to amps through sun roof and over the car and noise stopped so I plugged originals back in and started car and noticed whe I pulled them out of rocker channel the noise stopped,after swapping back and forth it didn't matter and trying to put them back in channel 1 at a time it did the same thing.
Could all of the new RCAs be bad?
What is the best brand I can run?
What's in that channel causing so much interference?

Thanks in advance
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Old 04-22-2013, 04:23 PM   #2
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What brand of RCA/amp kit did you buy? I've never liked those amp kits they sell. Most of them are not properly shielded and use cheap metal threads which cause distortion and noise. I'd stick with common brands like Rockford, DB Link, Stinger, Monster, and Tsunami. Brands like Pyle and boss give you cheap cables that will make all the money you spent on speakers, subs, amps, and HU worthless. Remember that a clean signal is key to a good sounding system. It dosent matter if you spent 2K on equipment if you are going to use cheap cables because garbage in is garbage out. Don't go overboard either and get some $50 set of RCA's. A good set will be about $15-$30.
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Old 04-22-2013, 05:08 PM   #3
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What brand of RCA/amp kit did you buy? I've never liked those amp kits they sell. Most of them are not properly shielded and use cheap metal threads which cause distortion and noise. I'd stick with common brands like Rockford, DB Link, Stinger, Monster, and Tsunami. Brands like Pyle and boss give you cheap cables that will make all the money you spent on speakers, subs, amps, and HU worthless. Remember that a clean signal is key to a good sounding system. It dosent matter if you spent 2K on equipment if you are going to use cheap cables because garbage in is garbage out. Don't go overboard either and get some $50 set of RCA's. A good set will be about $15-$30.
the twisted set are rockford and the other two are stinger
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Old 04-22-2013, 05:11 PM   #4
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Have you checked you ground connection?
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Old 04-22-2013, 06:21 PM   #5
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Have you checked you ground connection?
Yes I had it grounded to battery then somebody suggested it needed to be grounded were old amp was grounded,then were old amp was mounted I sanded a spot down to bare metal and tried there,it didn't change any any location,I have a ground wire tied into HU ground and ran all the way back to were amps are grounded in the trunk and I also read were pioneer HU have weak grounds on there RCAs so I even laced them
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Old 04-22-2013, 09:54 PM   #6
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ground the amps to the battery. next run the RCAs away from any factory wires. try to avoid running it parallel with the factory wire. that should eliminate the groundloop noise your getting. also check you gain settings on the amps.

@ albarran9.. pls explain cheap metal strands that cause distortion and noise. Also clean signal is generated from the source unit and not from the rca. as far the rca you listed as good MONSTER Cable is the only one i see as good... all the other you have listed are made in the same... if you dont believe me cut them and look inside. not flaming just stating the obvious.
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Old 04-22-2013, 10:34 PM   #7
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Grounding to the battery is not a good idea. You want the grounds to be to a chassis ground. Going straight to the battery can induce noise.
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Old 04-22-2013, 11:15 PM   #8
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lets look at the electrical system

charge from alternator (car on) to battery. + terminal wired to fuses to the car then to equiptment. - terminal of battery grounded to chassis of the car. all equiptment grounded different points of the car chassis.

the entire car chassis can produce noise. grounding it to the chassis i like grounding it to the (-) terminal of the battery.

Almost all car audio is based off of 12v dc which requires a circuit to operate. What it means is that you need to have 12v coming in from the alternator/battery and it must return to the battery via a ground. (Purists: Yes, 12v actually runs from - to + in US vehicles, but lets not confuse the point). Electricity is sneaky, and rather moody. It will try to find the easiest path to create this circuit. We want to ensure that its easiest and most efficient route is through the ground wiring of the unit. This brings us to our first potential cause for your noise.

Most modern cars are built on the uni-body concept. Metal portions are tacked together with high power tack welders. The welds are awful for grounds and can cause a real hassle.

care should be taken for your 12v+ wiring. Make sure you use good crimps, adequate gauge wiring and LOTS of contact at every connection. That means your connection to the battery should have a ton of surface to surface contact. The more the better as I have seen numerous people just shove a little bit of a ring terminal into the battery terminal. This does NOT make the proper type of connection. I usually tug on my wiring after i connect it. Give it a decent tug. If it comes loose, it wasnt a good enough connection/crimp.

Our next potential cause of noise is something called Electromagnetic Interference...

This stuff is everywhere. Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. This interrupts, obstructs, or otherwise degrades or limits the effective performance of those other circuits. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of spurious emissions and responses, intermodulation products, and the like. It is also known as Electromagnetic Interference or EMI

What this means is that if you are not careful with the quality of your components and where you place them, they hold a strong chance of picking up EMI. Shielding on cables can help reduce this effect but the cost of cables is rediculous. A standard RCA cable from a decent manufacturer purchased outside of Radio Shack should be sufficient. Looking for single shielded cable. Plan on spending about $1.00 to $1.50 a foot. These cables are very important to your system and should not be the weakest link. Make sure you route your cables as far away from RFI sources as possible. Your power cables are a source, your PC is a source, strange electrical component boxes around the vehicle are sources. Basically anything that carries an electric signal can produce this unwanted nuisance. Keep your cables as far away as possible from them all.

Grounding a components chassis can help create a shielding barrier by passing the interference back into the ground. Depending on how the system is designed, this can be good or bad as it can create a ground loop.

Some amplifiers will also pick up EMI. Usually these are inexpensive amps where they cut corners in the design. If you have determined your amp is the problem, try mounting the amp to metal. It may help the situation. HUGE NOTE: grounding the chassis of an amp can cause the exact symptoms we are trying to avoid, so only try this in your trouble shooting process. I usually recommend AGAINST mounting directly to metal.
Keep in mind that those external crossovers (passive AND active) can also pick up EMI. Be careful where you place them.

Finally the most famous culpret... The Ground Loop.

In electrical engineering and electronics, a ground loop refers to an unwanted current that flows in a conductor connecting two points that are nominally at the same potential, for example ground potential, but are actually at different potentials. In english, this means that one component has found it easier to ground itself through another component.

If a component does NOT have a proper ground, it will look to ground itself through the easiest means. This is by grounding through the next component down the line. How does it do this? Through those nifty RCA cables. The outer shielding of the RCA cables is actually a common ground (in most cases). If your PC's ground is not so great, it will try to ground itself through your amplifier's ground by passing its ground through the RCAs and into the amp. This is where all that noise comes from. This can happen if the ground potential of any one component is higher/lower than another. We combat this by making sure our ground are sufficient

Finally, how do we troubleshoot a system?

Isolation, Isolation, Isolation

We have to separate each piece from the system and test it. Consider the system below:

[Source (PC, HU)] ----> [amplifier 1,2,3...n] ----->[passive crossover] ----->[speakers]

from your test just isolate the rca wires... DONE
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Old 04-23-2013, 12:31 AM   #9
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Nice write-up.
This is why you ground to the chassis and not the body.
All that noise, when the amps are grounded to the negative terminal of the battery, comes from the differential between the HU ground (body) and the amp ground (battery).
If you look at the amount of noise that can be seen at the battery itself from the car's normal charging and discharging you can find that it is anything but clean.
Another reason not to use the battery is safety. Now understand that this is something I've read and never seen, but hey.... If the strap between your car and the battery fails, as you've pointed out the flow will still find ground. What's in line with that? Your amps. Is this something that you'd ever see? Maybe not, but there is still no reason to risk it either.

At the end of the day you can ground to the battery, but in many circles it is not considered good practice.

Your choice.
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Old 04-23-2013, 06:43 AM   #10
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I've had the grounds connected to the lug were the negative cable from battery connects with a crimped and shrink tube lug with a 14 gauge wire I ran to HU and spliced with factory ground.I have moved grounds from battery to factory amp ground on left side and even sanded to bare metal and connected to bolt on factory amp rack.
I tried with second ground disconnected
The amps are mounted to sub box and I ran a jumper wire from amp chassis to ground
I swaped amps thinking internal grounds were bad(I have never had a problem with a p series amp)
I laced all the RCAs on the back of HU thinking internal ground in it was bad
The strange thing is I don't think it is alternater noise because when you give the car a little gas it goes away its only when car is idling
What runs in that left side?
I took factory amp and sub out and tied into speaker wires for speakers from there
The only way I could run them further away is take out seat and run them through middle of floor pan,but I would have a hard time believing that's the issue not unless this is just a bmw thing
I guess I am going to buy 3 new sets of RCAs and go from there

Thanks for all the input
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Old 04-23-2013, 06:58 AM   #11
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Per amp output noise

Some cases it's unavoidable due to source unit design or an added source of noise being present.
Try a RCA noise suppressor.. Sometimes this is enough to make you smile again without bleeding out your wallet. Albeit band aid. But works when alternatives aren't viable.


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Old 04-23-2013, 06:59 AM   #12
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Per amp output noise

In your case multiple RCA noise suppressors...
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Old 04-23-2013, 07:03 AM   #13
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In your case multiple RCA noise suppressors...
Will they limit sound in anyway?
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Old 04-23-2013, 07:10 AM   #14
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Per amp output noise

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Will they limit sound in anyway?
Not noticeable. But in saying that.. They suppress. That's it's job.
I've used them before in earlier years with cheap cheap amps and it works.
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Old 04-23-2013, 07:14 AM   #15
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Per amp output noise

I just found this too:
http://www.crutchfield.com/S-TAb5NIq...car/noise.html
Give it a look.
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Old 04-23-2013, 05:14 PM   #16
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I just found this too:
http://www.crutchfield.com/S-TAb5NIq...car/noise.html
Give it a look.
Thanks for all the input I think this weekend I'm going to switch the 2 non twisted RCAs for twisted and see how I can get them away from the left rocker maybe beside center console or the RCA noise suppressors
I guess I will flip a coin
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Old 04-23-2013, 08:40 PM   #17
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In your case multiple RCA noise suppressors...
Quote:
Originally Posted by Jimfred View Post
Will they limit sound in anyway?
BTW when I said multiple, I don't mean inline, I mean 1 per RCA pair.
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Old 04-23-2013, 09:52 PM   #18
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Originally Posted by Jimfred View Post
I've had the grounds connected to the lug were the negative cable from battery connects with a crimped and shrink tube lug with a 14 gauge wire I ran to HU and spliced with factory ground.I have moved grounds from battery to factory amp ground on left side and even sanded to bare metal and connected to bolt on factory amp rack.
I tried with second ground disconnected
The amps are mounted to sub box and I ran a jumper wire from amp chassis to ground
I swaped amps thinking internal grounds were bad(I have never had a problem with a p series amp)
I laced all the RCAs on the back of HU thinking internal ground in it was bad
The strange thing is I don't think it is alternater noise because when you give the car a little gas it goes away its only when car is idling
What runs in that left side?
I took factory amp and sub out and tied into speaker wires for speakers from there
The only way I could run them further away is take out seat and run them through middle of floor pan,but I would have a hard time believing that's the issue not unless this is just a bmw thing
I guess I am going to buy 3 new sets of RCAs and go from there

Thanks for all the input
do you have a volt meter? test your voltage when idling.. then voltage when you rev / when the noise dissappears
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Old 04-23-2013, 10:00 PM   #19
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here a FULL TS guide for noise in the system:

One word of warning is that some HU's and/or processors nowadays have a zero bit mute, which essentially cuts off the output during low signal passages to reduce noise.....so be aware if this is a feature your unit has. Onward to the guide;

How can you eliminate alternator whine in a car audio system?

If you have alternator whine in a car audio system and want to get rid of it, there is only one sure-fire way to do it. David Navone and Richard Clark from Autosound 2000 in the USA developed the following step-by-step instructions. If you follow the instructions EXACTLY, you are guaranteed to trace and eliminate the noise in your car audio system. Don't miss a step and don't assume that something is OK without checking it.

Each time you check for noise, you should do it with the engine running at 1500 to 2000 rpm and the headlights on full beam so that the alternator will be charging. The tests with the CD player connected should be done with a 'zero bit' track playing and the volume at maximum. Set your CD player to 'repeat' if it has that feature.

Safety. Make sure when doing noise tests that the parking brake is on and working, and that the vehicle is in neutral or 'park'. Perform these tests in an area with good ventilation or use an extension hose on the exhaust to route the fumes outside.

Step 1. Check the Amplifiers

1a. Unplug the RCA cables from the amplifier/s and mute the signal at the input by using shorting plugs. This will isolate the amplifier from the rest of the car stereo installation. You can make shorting plugs by taking cheap male RCA plugs and soldering the centre and outer terminals together. This shorts out the input of the amplifier/s to ensure that it has zero signal.

Has the noise gone?
Yes. Go straight to Step 2. Reduce The System.
No. Go to 1b.

1b. Disconnect the speakers from the amp and connect a pair of test speakers to it. Make sure the test speakers are not in contact with the car body. The purpose of this step is to ensure proper isolation of the speakers and the speaker leads from the car's chassis.

Has the noise gone?
Yes. Check speakers, speaker leads and passive crossovers for proper isolation from the car's chassis. Shift passive crossovers to a location away from power cables and the car's body.
No. Go to 1c.

1c. Isolate the amplifier from the chassis of the car. There must not be any electrical contact between the car's chassis and the amplifier, except for the grounding point.

Has the noise gone?
Yes. Reinstall the amplifier isolated from the chassis of the car. Make sure that the amplifier is grounded in just one point.
No. Go to 1d.

1d. Supply the amplifier with an isolated power source, for example an external car battery or a 12-Volt DC power supply.

Has the noise gone?
Yes. Noise is entering the amplifier via the power supply, try changing the grounding point and add external power supply filtering. Consider changing the amplifier.
No. The amplifier has some severe problems, is totally isolated and still noisy. Replace it or have it repaired.

That is the end of Step 1. You have now either eliminated the amplifier and speakers as a problem or you have replaced a faulty amplifier. Now you can go on to Step 2.

Step 2. Reduce the System.

2a. The amplifier is known to be OK. It is now time to disconnect any signal processors (equaliser, electronic crossover, etc.) and connect the signal from the output of the head unit directly into the input of the amplifier.

Has the noise gone?
Yes. The noise source must be either one or more of the processors or possibly the signal route. Go to Step 3. 'Add Signal Processors'. If you didn't have any signal processors and you are using the signal cable in its normal, installed route then the problem is solved.
No. Go to 2b.

2b. Run new signal cables over a new route between the head unit and the amplifier.

Has the noise gone?
Yes. Permanently route the signal cables in the new route. Go to Step 3. 'Add Signal Processors'. If you don't have any signal processors then your problem is solved.
No. Go to 2c.

2c. Isolate the case of the head unit from car's chassis. There must not be any electrical contact between the head unit and car chassis except for a single grounding point. Beware of antenna grounds and pullout cases!

Has the noise gone?
Yes. Reinstall the head unit isolated from the car's chassis and any other metal parts in the dash. Ground the head unit at one point. Go to Step 3. 'Add Signal Processors'. If you don't have any signal processors then your problem is solved.
No. Go to 2d.

2d. Move the head unit ground to a quieter grounding point. Test a number of points and also try grounding the head unit to the same point as the amplifier.

Has the noise gone?
Yes. Reinstall the head unit using the quiet grounding point. Go to Step 3. 'Add Signal Processors'. If you don't have any signal processors then your problem is solved.
No. Go to 2e.

2e. Move the head unit as near to the amplifier as possible. Then connect output of the head unit to the amplifier with the shortest possible RCA cables.

Has the noise gone?
Yes. Reinstall the head unit one step at a time. Check for noise after each step during the reinstallation. Once you have the head unit installed, noise free go to Step 3. 'Add Signal Processors'. If you don't have any signal processors then your problem is solved.
No. Go to 2f.

2f. Supply the head unit with an isolated power source, for example an external car battery or a 12 VDC power supply. Make sure that car chassis is not in contact with the head unit.

Has the noise gone?
Yes. The head unit is sensitive to noise in the supply voltage. Add power supply filtering to the supply voltage for the head unit or use an isolated power supply. You may be better to change the head unit. Once you have a head unit installed noise free, go to Step 3. 'Add Signal Processors'. If you don't have any signal processors then your problem is solved.
No. There is a serious problem with the head unit. Go to Step 4 'Check the Vehicle' and/or change the head unit.

Step 3. Add Signal Processors.

At this level the amplifier is known to be good. The car's electrical system is OK and the reinstalled head unit is working fine when connected directly to the amplifier.

3a. Connect one of the Processors back into the signal path.

Has the noise gone?
Yes. Go to 3a for the next processor. If there are no more processors, the problem is solved.
No. Go to 3b.

3b. Run new signal cables over a new route between the Head-unit and processor and between the Processor and the amplifier.

Has the noise gone?
Yes. Permanently route the cables on the new quiet path. Go to 3a for the next processor. If there are no more processors, the problem is solved.
No. Go to 3c.

3c. Isolate the processor from the car's chassis except for a single grounding point. Connect the processor ground to the same grounding point as the head unit.

Has the noise gone?
Yes. Provide isolation between the Processor and the car's chassis and permanently route the cables on the known quiet path. Go to 3a for the next processor. If there are no more processors, the problem is solved.
No. Go to 3d.

3d. Since new cables and re-grounding does not help, it is time to relocate the processor very near the amplifier. Connect the output of the processor to the amplifier with the shortest possible RCA cables.

Has the noise gone?
Yes. Reinstall the Processor one step at a time. Check for noise after each step in the reinstallation. Be careful when routing the signal cables. Remember that the car's chassis is a conductor. Go to 3a for the next processor. If there are no more processors, the problem is solved.
No. Go to 3e.

3e. Power the processor with an isolated power supply. Do not let the processor touch the chassis of the car.

Has the noise gone?
Yes. The processor's power supply in not sufficiently isolated from its audio circuitry. Either replace it or consider the permanent installation of an isolated power supply (1:1 DC/DC converter). This type of device provides a permanent power source that is well isolated from the car's chassis. Go to 3a for the next processor. If there are no more processors, the problem is solved.
No. Go to 3f.

3f. Physically separate the processor and the isolated power supply from the rest of the system by many metres. Use long signal cables.

Has the noise gone?
Yes. Something is seriously wrong with either the processor or your install/test procedures. Please repeat this level from the beginning.
No. Change Processor -- this one has design problems. Go back to 3a for the new processor.

Step 4. Check the Vehicle

The suspect car's charging and electrical systems can be checked by using the previously installed sound system in a "known quiet" car.

4a. Connect jumper cables between the batteries of the two vehicles and start the engine of the suspect car. Turn on the headlights on the suspect car and listen to the stereo on the "known quiet" car.

Is there now noise in the quiet car's system?
Yes. Have a qualified auto electrician check out the car's charging system.
No. The suspect car's alternator and charging system is now proven to be quiet. The problem must lie in the car stereo installation -- not in the vehicle.

This the Process I have done in all the cars I have built for IASCA in the past and other SQ cars for customers..
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Old 04-24-2013, 05:22 AM   #20
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do you have a volt meter? test your voltage when idling.. then voltage when you rev / when the noise dissappears
At the battery or alternater?
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