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What is the technical side of ground loop / alt whine noise?
It seems interesting to me that a ground loop in the electrical system can lead to noise through the amp and speakers. Since you have a very large cap bank in the power supply of your amp, shouldn't that be filtered out and never make it into the signal output side?
Do the caps in the power supply just not allow for enough filtering of the signal, so the modulated power fed to the amp is what is being boosted to create the amplified audio output? But If that's the case, why doesn't alt noise not get louder in proportion to volume of the amp?
This question comes from me having alt whine currently, and another strange symptom. With no RCAs plugged into the DSP that is the only signal source of my amps, i still get very quiet output of whatever my headunit is playing when I turn the volume up to check for noise floor. And in trying to figure out why, I started thinking that maybe the audio signal is somehow making it's way from the headunit into the cars power/ground, and that signal making it's way to the speakers through the amp.
Anyone have any info on how a ground loop becomes audible, or any other strange noise in a system comes about?
 

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Ground Loops are a form of a Faraday Loop where any metal that's interconnected to any portion of the loop can act as a pickup for any stray EMF which will induce a voltage on that Loop and create hum. 99.9% of hum and whine caused by ground loops is on the signal side and not the power side since the signal side has such small voltage swings any induced current can create substantial noise. But that noise doesn't increase with volume since the induced current doesn't change only the original signal does which can often drown out the injected noise.

It's all about having two different points in an interconnected system at two different potentials (two different paths back to the main ground), the difference in potential causes a difference in voltage which creates the inductive pickup through a conductive loop, it's even worse in buildings where the entire buildings electrical wiring can become part of that pickup and induce noise from anywhere. Any rotating (alternator) or fluctuating (AC Current) magnetic field will then create current in the loop, if that loop is of low enough impedance (good grounds but just slightly different potential) then the alternating magnetic field created by the MOSFETs in the HU could theoretically induce those currents in a modulated way that would carry the original audio signal.
 

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2006 Toyota Camry LE 2.4L - Seeing how good I can make cheap components sound.
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What is the technical side of ground loop / alt whine noise?
It seems interesting to me that a ground loop in the electrical system can lead to noise through the amp and speakers. Since you have a very large cap bank in the power supply of your amp, shouldn't that be filtered out and never make it into the signal output side?
Do the caps in the power supply just not allow for enough filtering of the signal, so the modulated power fed to the amp is what is being boosted to create the amplified audio output? But If that's the case, why doesn't alt noise not get louder in proportion to volume of the amp?
This question comes from me having alt whine currently, and another strange symptom. With no RCAs plugged into the DSP that is the only signal source of my amps, i still get very quiet output of whatever my headunit is playing when I turn the volume up to check for noise floor. And in trying to figure out why, I started thinking that maybe the audio signal is somehow making it's way from the headunit into the cars power/ground, and that signal making it's way to the speakers through the amp.
Anyone have any info on how a ground loop becomes audible, or any other strange noise in a system comes about?
From my very simple understanding, a ground loop is a difference in ground resistance between two components, leaving a few stray mV at one end that wants to go to full ground. The easiest path is through the signal wires to the ground of the better grounded component. This very small current is enough for the very sensitive input circuitry of an amplify to pick up and amplify into a higher pitch steady tone.

If I'm wrong I hope someone corrects me. This simplified explanation makes sense to me given my limited basic electrical circuits understanding.
 
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