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<blockquote data-quote="Mike Sokol" data-source="post: 64389" data-attributes="member: 1989">Re: Lighting system causes buzz/hum in the circuit breaker panelsExactly right.... and using different phases generally has nothing to do with hum or buzz. That&#039;s an old-wives tale....In my experience, neutrals with noise often contaminate the safety ground bus with all sorts of induced voltages. But remember that even a &quot;clean&quot; neutral that&#039;s been accidentally double bonded at a sub panel will induce 60-Hz ground loop hum (without harmonic content). That&#039;s because there&#039;s always some kind of voltage drop in a neutral (or any wire) carrying current. All you have to do is poke your DMM between the neutral and ground pin of a properly grounded outlet and you&#039;ll generally find a volt or two difference if there&#039;s anything turned on in the building. If you don&#039;t see that normal voltage difference, then some ill-informed electrician has bonded the neutral and ground bus&#039;es together in a sub panel trying to make a &quot;better&quot; ground. That&#039;s a violation of the NEC, but happens all the time to me, even in new buildings. That&#039;s what seems to induce 60-Hz ground loop current &quot;hum&quot;, while higher frequencies on the neutral from triac dimmer spikes or Triplen currents from 3-phase Delta wiring seem to cause the &quot;buzz&quot;. Yikes.... I still contend that you can figure out the best place to begin troubleshooting audio system noise by just listening to the frequency and harmonic content of that noise. Of course it helps if you&#039;re a musician (I&#039;m one of 56+ years), but a simple RTA FFT program will show you what your sound system &quot;noise&quot; is composed of. Not a 100% obvious identifier, but certainly a start. Also, a clamp-on ammeter around the exterior of an XLR mic cable with show 60 Hz &quot;ground loop&quot; currents rather easily since they&#039;re on the order of 1 amp per 1 volt of ground differential. I&#039;ve done a lot of experimenting with this on the bench, and have included a picture of the portable demonstration kit from my No~Shock~Zone and ASSIST installer seminars. Note the little red &quot;Glo-Melt&quot; resistance soldering transformer in the middle which I&#039;ve wired to inject up to 3 volts and 30 amps of ground-loop hum between any two pieces of audio gear. In class we use a bunch of different brands of amplifiers and active speakers to listen for the &quot;pin 1 problem&quot; as it&#039;s often called. Good times.... :lol:Mike Sokol</blockquote>

[QUOTE="Mike Sokol, post: 64389, member: 1989"] Re: Lighting system causes buzz/hum in the circuit breaker panels Exactly right.... and using different phases generally has nothing to do with hum or buzz. That's an old-wives tale.... In my experience, neutrals with noise often contaminate the safety ground bus with all sorts of induced voltages. But remember that even a "clean" neutral that's been accidentally double bonded at a sub panel will induce 60-Hz ground loop hum (without harmonic content). That's because there's always some kind of voltage drop in a neutral (or any wire) carrying current. All you have to do is poke your DMM between the neutral and ground pin of a properly grounded outlet and you'll generally find a volt or two difference if there's anything turned on in the building. If you don't see that normal voltage difference, then some ill-informed electrician has bonded the neutral and ground bus'es together in a sub panel trying to make a "better" ground. That's a violation of the NEC, but happens all the time to me, even in new buildings. That's what seems to induce 60-Hz ground loop current "hum", while higher frequencies on the neutral from triac dimmer spikes or Triplen currents from 3-phase Delta wiring seem to cause the "buzz". Yikes.... I still contend that you can figure out the best place to begin troubleshooting audio system noise by just listening to the frequency and harmonic content of that noise. Of course it helps if you're a musician (I'm one of 56+ years), but a simple RTA FFT program will show you what your sound system "noise" is composed of. Not a 100% obvious identifier, but certainly a start. Also, a clamp-on ammeter around the exterior of an XLR mic cable with show 60 Hz "ground loop" currents rather easily since they're on the order of 1 amp per 1 volt of ground differential. I've done a lot of experimenting with this on the bench, and have included a picture of the portable demonstration kit from my No~Shock~Zone and ASSIST installer seminars. Note the little red "Glo-Melt" resistance soldering transformer in the middle which I've wired to inject up to 3 volts and 30 amps of ground-loop hum between any two pieces of audio gear. In class we use a bunch of different brands of amplifiers and active speakers to listen for the "pin 1 problem" as it's often called. Good times.... :lol: Mike Sokol [/QUOTE]

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