Reply to thread

Message

<blockquote data-quote="helotaxi" data-source="post: 1424303" data-attributes="member: 550915">Actually, thinking about it, it should be 6x the alt RPM.&nbsp; The noise that you hear is the ripple voltage left over from the rectification process.&nbsp; The direct output of an alternator is 3 phase AC.&nbsp; The rectifier basically flips the neg swing of each phase over to the positive.&nbsp; The result is DC with a slight pulse six times (once each for the pos and neg of each phase) for every revolution.&nbsp; Check out the picture below.<img src="http://members.1stconnect.com/anozira/SiteTops/energy/Alternator/alt_03_1.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />The first is straight DC, basically what it coming from your battery.&nbsp; The last is what you get from a properly working alternator.&nbsp; Notice the ripple at the top.&nbsp; Alot of people that are getting really bad noise (especially radiated noise) have a bad winding on their alt so the resulting voltage is somewhere between the second and the third diagram with a really pronounced ripple.&nbsp; As long as this ripple is kept out of the signal path, you will never hear it.&nbsp; It doesn&#039;t really cause a pulse in the power that is seen by your audio components because they have capacitors in the power supply that effectively filter it out.&nbsp; If the signal section of the component is not electrically isolated from the power section, the ground differential between the various components of the system will use the path of least resistance (in many cases the shielding of the signal cable) to equalize the ground potential.&nbsp; Once this ripple is introduced into the signal chain, you&#039;re going to hear it.</blockquote>

[QUOTE="helotaxi, post: 1424303, member: 550915"] Actually, thinking about it, it should be 6x the alt RPM. The noise that you hear is the ripple voltage left over from the rectification process. The direct output of an alternator is 3 phase AC. The rectifier basically flips the neg swing of each phase over to the positive. The result is DC with a slight pulse six times (once each for the pos and neg of each phase) for every revolution. Check out the picture below. [IMG]http://members.1stconnect.com/anozira/SiteTops/energy/Alternator/alt_03_1.gif[/IMG] The first is straight DC, basically what it coming from your battery. The last is what you get from a properly working alternator. Notice the ripple at the top. Alot of people that are getting really bad noise (especially radiated noise) have a bad winding on their alt so the resulting voltage is somewhere between the second and the third diagram with a really pronounced ripple. As long as this ripple is kept out of the signal path, you will never hear it. It doesn't really cause a pulse in the power that is seen by your audio components because they have capacitors in the power supply that effectively filter it out. If the signal section of the component is not electrically isolated from the power section, the ground differential between the various components of the system will use the path of least resistance (in many cases the shielding of the signal cable) to equalize the ground potential. Once this ripple is introduced into the signal chain, you're going to hear it. [/QUOTE]

Verification