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120 Posts
Discussion Starter · #1 ·
I battled with alt whine before when I first setup my system. I tried basically everything to troubleshoot the problem i.e. Big3, move HU ground, reseat amp ground, ground HU and amp to same spot, run power opposite of speaker and signal wires, etc.

The only conclusion that we were able to come up with was that the problem was radiated noise coming in the RCA's. The solution was to move the RCA's and route it through the middle of the car. It worked.

I recently upgraded to a fully active system. Added another sub amp and have my existing 4 channel amp to power the front stage.

The noise came back.

So now that the noise has come back, the RCA's shouldn't be a problem right? What changed? Probably the amp layout. I unplugged the rca's on the HU. The noise is still there but very faint - couldn't really hear it unless i put my ear next to the tweeter or mid. Next, I unplugged the rca's on the 4 channel amp. The noise is still there but also very faint.

I'm thinking its the amp? What other steps should I take to make sure? Unplug the speaker leads on the amp?

The ground of the amps (4ga.) are screwed in pretty good and are next each other. I'm using the same area to ground the amps as before and I didn't have any problems.

DIYMA Founder
4,757 Posts
Ground loops... and poor isolation in your equipment between signal and power grounds. Easiest thing to do is replace the amp, or use isolating transformers on your rca's. There's alot of touch and go voodoo that sometimes works too, like moving the power ground around or re-routing the rca's.

329 Posts
rbenz27 said:
I unplugged the rca's on the HU. The noise is still there but very faint - couldn't really hear it unless i put my ear next to the tweeter or mid.

Next, I unplugged the rca's on the 4 channel amp. The noise is still there but also very faint.
Bummer. If you disconnected the RCAs, then it sounds like an amp issue if the amp is grounded well. If you have a long cable, you might loosely run a cable to the battery ground to see if it goes away then. There are differing opinions on running a ground to the battery, but this could be a good test to see if the problem is ground related, or simply the amp itself.

As for RCAs, I purposely run directional cables with the shield only connected on one end. This came from pro audio wiring back in the day.

Another thing is to run another set of RCAs in the car (not under carpet, etc) to see if that changes anything.

Got those tweeters yet? ;)

120 Posts
Discussion Starter · #4 ·
I might be crazy but it appears that the noise got louder last night. Hmm.. It might be because I was running headlights, AC, etc.

I'm tired of troubleshooting lol. I worked a lot on getting rid of the noise before, now it came back I might settle for a GLI band-aid fix.

I never heard of isolating transformers for RCA's, does it affect SQ like GLI's?

Focus, yeah I got the tweets in the mail! Did you get yours yet?

204 Posts
I have similar noise and have been troubleshooting for well over a year (yes I am slow and lazy). A cheak Rockford GLI got rid of MOST of the noise but as you said - I would like to find the cause.

I have replaced amps, swapped headunits, swapped RCA's, reran RCA's, new speakerwire, moved my passive crossovers fromt he kicks to the back of the car, tried grounding my RCA's (added noise), tried different grounds for the HU, and several other things.

The only thing I haven't tried is changing my amp grounds and straightening up the wiring by the amps, If that doesn't work I might try new spark plugs (read about several people who solved their noise that way).

693 Posts
check out the tech articles on

here's a copy/paste for noise troubleshooting. it's long but it's good info to have.

The following checklist can be used for the basic troubleshooting of noise in mobile audio installations. The key to success is to relax and systematically go through the vehicle. The problem WILL be found. Murphy’s Law states, however, it will be in the last place you look.

1. TO BEGIN: Be sure that system is correctly designed and matched for compatibility.

2. INSPECT VEHICLE: Verify ground from negative battery terminal connections to the fender and/or chassis. Upgrade as needed. This connection must be capable of handling all the current flow requirements of the system. ASSUME NOTHING, oversize as needed.

3. CHECK VEHICLE ELECTRICAL SYSTEM: Battery, alternator, etc. Make sure your alternator can adequately supply the sound system as well as other vehicle systems (alarm, lighting, etc.) AMPS/VOLTAGE NOT OK: See service technician to have system repaired or upgraded.

4.1 Electrically isolate them from the chassis.
4.2 Mount away from vehicle harnesses, computers, etc.
4.3 Do not hesitate to use a factory wiring diagram if needed. DO NOT GUESS!

5.1 USE CORRECT GAUGE WIRE. If in doubt, go larger.
5.2 Ground all components to a central point and/or use a "ground sniffer" to locate a quiet area.
5.3 Run power and signal cables down opposite sides of vehicle.
5.4 Properly terminate all connections (double check!).
5.5 Use a relay to provide clean power to accessories if needed.
5.6 Use the same gauge wire for power and ground.
5.7 Check signal cables for continuity and repair any open shields or cold solder points.
5.8 Ensure that the shield of signal cables, especially RCA ends are not touching the chassis.

6. HOOK EVERYTHING UP: Follow the instructions provided with the component and be sure of polarity. Make sure everything is working and set all line levels. If noise exists, please continue...

7. IGNITION NOISE: Check for noise in each of the following switch positions:
7.1 IGNITION ON, CAR NOT RUNNING: It is possibly related to an Electronic control module, digital dash, or possibly fuel pump. Do not attempt to filter an E.C.M.! Re-route cables away from control unit or fabricate a shield.
7.2 ACCESSORY POSITION, CAR NOT RUNNING (All accessories off): Substitute an isolated signal source (such as a walk-man CD, tape player, or home CD player), if the system plays fine, the head unit needs to be checked.
7.3 ENGINE RUNNING: Make certain no ground loops exist between components (if they do, see next section.).

NOTE: Pulse Width Modulated headlight switches (like some Honds cars use) can cause a whining type of noise when on, verify this type of problem by turning lights on and off while listening for noise. If this is the problem, the headlight switch may need to be replaced with an alternate type.

8. GROUND LOOPS AND/OR RADIATED NOISE EXIST: Check resistance of all ground cables; consider using central point grounding. Resistance needs to be as low as possible (around .2 ohms) on your meters lowest scale. If not, re-do or upgrade cables. If it is not possible to get the resistance’s this low, try to get them all at an equal value (all the same resistance.)

TIP: Use the combination of a DVM and a ground sniffer to find the best ground point. Remove the positive cable from the vehicles’ battery and check resistance’s from:
A. Ground point of all units with connection point on chassis.
B. Connection point on chassis with the negative terminal of the systems battery.
C. Battery negative terminal with the chassis connection point.

8.1 RADIATED NOISE: Place head unit next to amplifier and plug directly in (or use an isolated source such as a Discman or Walkman) and turn system on. Listen for noise. If noise is gone, please continue...

Muting plugs can be used to systematically troubleshoot the point at which the noise is entering the system. Muting plugs consist of a male RCA end with the positive and negative (tip and shield) connected together (a dead short). Open RCA ends can become an antenna radiating noises into a sound system. By inserting muting plugs into the inputs of each component in your system one at a time the source of the noise can be found.

This is a process of elimination starting with your amplifiers. Insert the muting plugs into the inputs of the amps. Turn on each amp (with the muting plugs inserted) one at a time and with the car running listen for noise. If none is heard, the amps are OK. If all amps are OK, connect the next piece in the signal path upstream of the amps (typically the crossover) by connecting its outputs to the amp inputs using normal RCA cords. Now insert the muting plugs into the inputs of that product and turn on the system. If noise is heard now, power the component with an external power supply. If the system is now quiet, the noise is probably entering through the components’ power supply. If no noise is heard, insert the plugs into the next component upstream in the signal path and check it the same way. Keep working your way upstream all the way to the head unit. Once the problem is found, you can stop.

9. ANTENNA NOISE I: Unplug antenna from the back of the head unit and listen for noise. If noise is eliminated, see section 13. ANTENNA NOISE II. However, if noise remains:
9.1 With head unit powered up and all speakers connected, slowly pull head unit from dash cavity and check for noise:
A. Noise Remains: Noise is entering on one of the power lines; ignition or memory. Install filter onto appropriate wire.
B. No Noise: The dash harness is radiating noise. Locate and re-route harness and shield entire harness next to the head unit. Isolate head unit chassis from metal dashboard.
9.2 If noise still remains, determine which of the following noises is present and suppress the noise at the source using the following sections:

NOTE: The following checks will not be necessary in most cases, but if the previous checks are not effective, continue.

10. IGNITION NOISE II: Determine the source of the ignition noise.
10.1 ONE OR TWO CYLINDERS: Try the following fixes in order:

A. Check for loose or defective spark plug wire.
B. Check for cracked rubber boots at the distributor or ignition coil(s).
C. Re-route plug wires away from car wiring or sensor leads traveling into passenger compartment.
D. Check for bad plugs (excessive gap).
E. Replace cap and rotor.
Note: you can often mist the ignition system with water to help sparks from failed equipment show up. Do this at your own risk of course.

10.2 ALL CYLINDERS: Try the following fixes in order:
A. Check ground from engine to firewall. Upgrade if needed.
B. Install a ground strap from the engine block to the chassis, as well as the hood.
C. Check heater core ground.
D. Check A.C. accumulator ground.
E. Move all wiring away from high energy ignition (H.E.I.) and plug wires.
F. Inspect H.E.I. ignitions, modules, and coils for the following and replace if needed:
1. Distributor cap; cracked, loose, or carbon build-up.
2. A rotor with burned black spot on wiper or pits in the surface.
3. Defective coil.
4. Oily film on lead terminals or inside of cap.
5. Defective ignition module (can cause ignition noise on FM only).

11. ACCESSORY NOISE: May be identified as a turn-on "pop", relay "pop", or other motor type noise.
A. Turn-on "pop" is usually due to components turning on before transients have a chance to settle. Delay the turn-on signal to suspect unit.
B. Relay "pop" is due to a component ground being at the same connection point as, say, the brake lights. Move the ground location. This can also be caused by excessively high gain settings.
C. Filter the power line to noisy motors (blower, etc) (check motor current draw for correct filter.)

12.1 CHECK ALL GROUND CONNECTIONS. If an audio component has some type of internal ground switches or jumpers, try changing settings.
12.2 CHECK ALL GAIN SETTINGS. Some components have gain built into their circuitry (either fixed or variable) and will increase signal levels. Gain controls are for matching signal voltage levels. They are not volume controls.
12.3 Check continuity of all RCA shield connections. Look for open or cold soldered connections.
12.4 On products with Balanced Differential Inputs, make sure no metal barreled RCA plugs are touching each other. This will defeat the differential circuit and create noise.
12.5 Eliminate all ground loops. (Refer to section 8: GROUND LOOPS.)
12.6 Install a cable from alternator ground to battery negative terminal along side the alternator charge wire using same gauge wire as main system power wire.
12.7 Install a filter on alternator output lead.
12.8 Have mechanic check alternator – repair or replace if necessary.

13. ANTENNA NOISE II: Fixed mast or power antennas go to section 13.2...
13.1 Windshield antennas: plug antenna back into radio and place aluminum foil over entire dash top and ground it with clip leads to door jamb switch.
A. NO NOISE: Use noise sniffer to locate which part of the dash the noise is generating from. After locating problem area, the following fixes are possible:
1. Line underside of dash with aluminum tape and run a ground lead to it.
2. If a noisy cable can be found, move it or shield it and ground the shield.
3. As a last resort, install a conventional antenna.
B. NOISE REMAINS: Measure resistance from antenna cable shield where it plugs into the head unit to a good ground using the lowest scale on DVM. Repair if necessary. Measure shield again. If ground is still bad, replace the antenna lead.
13.2 Fixed mast or power antennas: Measure antenna ground from shield at plug end to ground on back of head unit using the lowest scale on DVM.
A. POOR GROUND: Disconnect and clean all RF connections. Check for a good ground at the antenna trim ring and mounting bracket. If the ground is poor, run a braided strap from the base of the antenna to a good ground. If noise remains, please continue...
B. GOOD GROUND: Try using a test antenna. The base must be grounded. Hold the base, not the mast.
1. POWER ANTENNA TEST: Disconnect antenna connector. Measure the resistance from the mast to the center conductor pin of the lead-in.
a. If resistance is less than 2 Ohms using the lowest scale on the DVM, measure from the mast to ground. If open (infinite resistance), suppress at the source.
b. If resistance is more than 2 Ohms, replace the antenna.
2. FIXED MAST ANTENNA TEST: Replace antenna.

14. You’re Done!

DIYMA Founder
4,757 Posts
Isolating transformers do affect the SQ, which is why you need to be careful to purchase one with the proper bandwidth and powerhandling for your application.

I'd also recommend David Navone's articles on troubleshooting noise at It helped solve alot of my noise issues.

muting plugs are worthy of elaboration ...

You can work backwards from the speakers to help identify the problem. But rememeber that all audio sources are designed to be a low impedance source, so to "mimic" them you need "short circuits". The thinking goes like this :

1. Disconnect the speaker wire from the speaker. But to mimic the amp driving the speaker, you have to short-circuit the speaker terminals right at the speaker. Chances are, the noise is gone ... the speakers certainly can't create the noise, and it's highly unlikely that noise is coupling directly into them.

2. Next we'll check the speaker wire. Disconnect the short circuit you put on the speaker in the previous step, and re-connect the speaker wire. But now, to mimic the amp, you must short the speaker wire at the amplifier end. Chances are, the noise will still be gone. It's unlikely (but possible) that noise is coupling into the speaker wire.

3. Next we'll check the amp. Disconnect the speaker wire short from the previous step, and connect the speaker wire to the amp. To mimic the processor/hu that drives the amp, we'll put muting plugs on the amp inputs. If noise returns, the problem is in the amp. If not, next step.

4. Next we'll check the RCA's. Unplug the muting plug from the amp input, and connect the RCA's. But in order to mimic the h/u driving the RCA's, you must short circuit the RCA's at the h/u end. If you don't, the open circuit on the driving end can create a different noise signature ... different impedances to ground, and interrupted loop, etc.

Well, you guys get the idea. Proceed one step at a time, making sure to "replace" the driving circuit with the appropriate short-circuit ... don't leave it open!

120 Posts
Discussion Starter · #10 ·
Ok. Here is what I've done so far following the steps outlined above.

- Unplugged speaker wires from the amp and shorted 'em. - No Noise
- Made some muting plugs, unplugged RCA's and plugged in the muting plugs - Got Noise with engine on. It got louder when all accessories are turned on and whined when gas pedal pressed.

So in conclusion.. The amp is the problem? I'm not sure how to fix it other than move the ground but I was using the same piece of metal as before without noise? I'm not sure if switching amps will get rid of the noise if there is an underlying problem like a weak battery or something...

204 Posts
I would try a different amp and see what happens - if you're desperate and don't have a spare one (or a friend with a spare) you can always take advantage of Best Buy or Circuit City's return policy and buy one with no intention to keep it.

Is the amp mounted to anything? If so - how so?

My noise went away with the muting plugs so swapping amps did nothing as expected.
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