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I connected the speaker output from my car audio player directly to speakers working fine for me. But i have to connect it with another speakers which is connected with an amplifier. So i reduce the output of player with "rca to low impedance converter". The amplifier audio is working fine by adjusting the gain in converter. But if the engine is on, the noise from the engine is present in the speakers. I connected the output from the player to the amplifier by adjusting the volume as its minimum(because its output is higher for amplifier) and the same noise is happening. The same amplifier is working fine by connecting aux input as my mobile phone inside the car and working fine without any engine noise. So i can prove that there is no noise from the power supply. So i confirmed that the noise coming from player audio output. It is not affected in directly connected speakers but affected amplifier speakers.

Car : Chevrolet Sail Uva 2013 model(India)

  • Can you describe the noise a little bit better what does it sound like, Etc? – mongo May 28 '17 at 12:04
  • Have you checked between the stereo in the car and the speakers to insure that they're not resting against something that would vibrate with the motor? I know in sound tech, one of the issues we have is basically cross-talk (from electronic or physical sources), which since the signal is analog, when amplified, create weird vibration sounds etc. when the sound comes out the speakers. – anonymous2 May 31 '17 at 17:28
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Generally, with audio system noise on cars I look for three kinds of things. First the most common source of noise is from an alternator. For example if the alternator has a failed diode there will be a very loud audio whine associated with it.

The second most common source of problems is with grounding. For example if there is a receiver, couple to an audio amplifier as an add-on unit for louder volume or for subwoofer comma and the units are not bonded together effectively, there can be current loops and other types of problems which can cause bad audio. These problems can be hard to track down, and the fastest way to resolve them is to run a wire between each unit making sure that it has effective bonding to the housing of the unit with screws.

The third most common source of problems is load related. For example a heavy load such as a cooling fan turning on and off rapidly can make clicking noises and thumping noises in an audio system. These problems are easier to find, especially if you have some instrumentation to detect the changing in load.

And your case, I would be very suspicious of your RCA to low-impedance converter. If you have poor bonding of that unit, or there is an impedance mismatch, then that connection is more susceptible to noise, including things like what would ordinarily be minor such as a tiny bit of alternator whine which many alternators will have even if they don't have a bad diode.

To help you further I think you need to identify for us a better description of your problem, specifically how does it sound, and a better understanding of what the exact connection is and what the devices for your RCA to low-impedance converter. I am wondering comma for example if you really need that converter.

Also you might indicate what the equipment is for your player and the equipment is for your amplifier. Try to find the specification for the amplifier input and for the player output. My guess is that there is some kind of a mismatch either level wise or more likely impedance wise which is causing your problem.

So it is possible that the filtering in your player is defective...At least on output. Can you connect the output of the player to a headphone?

Also please do one more thing...Make sure things work right without the engine running but with everything connected the way you want it to be.

There when there is one additional thing that I have to bring up. That is that impedance mismatch as can make motor boating noises. It's not exactly with the engine RPM but it may vary with the voltage of the system, which varies a little bit with engine RPM. We need to make sure that your system is not motorboating. If you have the car idling and you have a certain noise comma and then you rapidly Zoom the engine, does the pitch change immediately? Or does it lag the zoom of the engine?

  • I connecter without rca to amp by decreasing the volum as low in the player also have the same noise. If i give my mobile as the input will not have the noise. So the noise is amplified on amplifier. Because the normal speakers not giving noice. – KIRAN K J May 30 '17 at 11:58
  • Is the noise different with the engine off? – mongo Jun 2 '17 at 7:48
  • yes. if engine is off, there is no sound – KIRAN K J Jun 2 '17 at 14:19
  • Good, can you disconnect the alternator, and see if there is the offending sound when the engine is running? Some alternators will unplug. If you pull a battery connection off the alternator, exercise precautions so that you do not have unintended shorts. – mongo Jun 2 '17 at 15:19
  • i need a circuit level solution – KIRAN K J Jun 2 '17 at 16:11
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Either ignition noise - sparks etc or a whine - from the alternator can be cured by purchasing and fitting suppressors designed for the job.

Take care as to the age of the car, details that you did not supply, as this may prevent the use of suppressors on the ignition system for example.

Other cures may involve improving the earthing between components with bonding straps - had to do this on the front suspension components on several cars due to static build-up from the disc brakes!

  • Car : Chevrolet Sail Uva 2013 model(India) – KIRAN K J May 9 '17 at 8:49
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The important thing is to find out what is causing the noise. Because the solution will depend on the reason. Follow the instructions here: noise suppression guide

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The likely cause is an audio input is active on your player. Check for hands-free microphones, On-Star (or similar) microphones or Bluetooth connections to your phone.

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