Trouble shooting amp noise.

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VW337
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Trouble shooting amp noise.

Post by VW337 »

Most amp noise within a vehicle can be classified into 2 main categories that are typically related directly or indirectly to the vehicle. In no way should you ever need to put in a “noise suppressor” or a “ground loop isolator” these are “patches” that will limit your systems capabilities. Check the end there is a “tech tips” section to virtually eliminate power related noises and some radiated noise problems before you ever begin an installation.

Radiated Noise:
Radiated noise is caused by something that is not directly connected to the installed audio equipment.

Most common things to pick up radiated noise: RCA’s, Passive Crossover, and Amplifier.

Things that will typically create radiated noise: Electric fuel pump, non-RFI spark plug wires, ECU, ABS control unit, SRS/Airbag control unit, Power steering assist control unit.

• Can be located with a noise-sniffer, which can be easily made from a portable cassette player with an extension wired in so that the tape head can be held out like a microphone.

Power Noise:
Power noise is the most common problem and is typically related to problems with the starting and charging systems of the vehicle.

Common symptoms: whining sound that changes when you move the gas pedal, noise when you first start the vehicle that gradually goes away after running for awhile, pops and clicks when you operate other vehicle systems.

Causes: weak battery, bad alternator, bad starter, bad ground, corroded battery terminals.

• Quick checks: check battery voltage- should be 12.3-12.6 volts with the vehicle off, and 14.4-14.7 volts while running.


Troubleshooting steps:

Pops and Clicks:
If you have pops and clicks run a common power and ground from your signal source to your amp, do not use the factory power and ground leads. If this does not work, check the battery voltage and upgrade the factory ground from the battery to the chassis.

Whining, Buzzing and Humming:

1. Disconnect the RCA’s directly at the amp. No noise, proceed to the next step; still have noise proceed to 6.

2. Disconnect the RCA’s directly at the head unit and reconnect at the amp. No noise, proceed to the next step; Noise, proceed to 11.

3. With the RCA ends near the signal source use a metal object to short the outside contact to the inside contact of the inputs to the amp. No noise, proceed to the next step; Noise, proceed to 11.

4. Run a 12+ and 12- lead (remember to fuse) from the signal source to a common point with the amp and then disconnect the existing +&- connections. No noise, you’re done; Noise, proceed to the next step.

5. Run a ground lead from the battery to the amp, disconnect chassis ground. No noise, you’re done; Noise, bench test amp try a different unit, or seek further assistance.

6. With no signal to amp, unscrew the unit and place a sheet of cardboard underneath the amp. No noise, proceed to the next step; Noise, proceed to 8.

7. Cut a piece of MDF or Plywood to the shape you want, and make it a finished piece, mount this to the vehicle and then mount the amp to it. Make sure the screws that you use to mount the amp do not go through the panel and make contact with the chassis of the car. No noise, you’re done; Noise, double-check the mounting screws.

8. Remove amp from the vehicle and bench test it, using a verified power and signal source. No noise, proceed to the next step; noise, replace amp and you should be done if not follow steps from the beginning.

9. Reconnect amp in vehicle and move to a different location, minimum of 18 inches away (if you cannot move the amp proceed to the next step). No noise, clean up wiring and mount it you are done; Noise, proceed to the next step.

10. Create a noise shield (instructions at the end) and place it under the amp. No noise, make it pretty and permanent you’re done; Noise, consider relocating the amp or find the source of the radiated noise and relocate it.
11. Disconnect RCA’s at the amp, using a DMM check the RCA’s for continuity. If good proceed to the next step; if bad plug in new set to test, proceed to 13.

12. Plug in a test set of long RCA’s to signal source and amp, routed over the roof line. No noise, proceed to next step; Noise, bench test the signal source, try a different unit, or seek further assistance.

13. Route the test RCA’s as close to the path that the original ones are on, but on top of the carpet. No noise, make permanent you’re done; Noise, proceed to the next step.

14. Route RCA’s down the opposite side of the vehicle. No noise, make permanent you’re done; Noise, try a better set of RCA’s, find the source of the radiated noise and relocate it, or seek further assistance.

How to make a noise shield:

To make a noise shield, take a piece of MDF and attach a thin sheet of aluminum to it with an adhesive. If you do not have aluminum available there are sound deadening products available that work as good as or better than aluminum (one is a sticky rubbery material with a metallic layer on that, and the other is two thin sheets of foam with a thin layer of lead between them). Make a short lead from the metal of the noise shield that can be connected to the ground of the equipment being shielded, try with and without wire connected to see which works best. Place shield with wood toward the noise and metal towards the electronics to be shielded.

Tech Tips

• Use a common power and ground point for your signal source and amp, processor, crossover etc…(do not use the factory supplied power and ground for the signal source it generates pops and clicks)

• Don’t just run the minimum recommended power cables step up to the next size.

• Run a power and a ground lead directly from the battery. The ground will degrade through the chassis of the vehicle via small factory chassis ground and spot welds.

• Upgrade the factory ground leads from the chassis to the battery and to the alternator (they’re usually very small).

• Never mount an amp directly to the vehicle metal, mount it a piece of wood or plastic so the chassis of the car and the chassis of the amp do not have an electrical connection of any kind.




To download full sheet CLICK HERE
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Bfowler
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Post by Bfowler »

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thedeal7235
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Post by thedeal7235 »

thanks for posting-it all makes sense now!!!!! Christian
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mhyde71
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Post by mhyde71 »

For me and for what it's worth.. I grounded my RCA's and that was it.. all set/wrapped up. Simply soldered a lil 16awg wire to the neg rca lead from head unit to the head unit (if that made sense)... basically gronded the neg lead from RCA's coming from HU.. all set. but from what i understand it was caused by the pioneer HU and those being famous for having noise/Junk running through their RCA's. maybe a help.. but there it is/
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