Amplifier pops when items unplugged

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sfav8r

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I was at a job today fixing a neutral-ground voltage problem (from a previous post). That problem is rectified, but the sound tech mentioned that when they have the amps on for the sound system, if they plug in any other equipment then unplug it, it makes a VERY loud pop. According to him, this was not a problem until after a large storm we had here two weeks ago (yes, we do get an occasional storm in San Francisco.

I checked it out and this does happen even if the thing being unplugged is not on the same panel as the AV equipment.

Any thoughts?
 
sfav8r said:
I was at a job today fixing a neutral-ground voltage problem (from a previous post). That problem is rectified, but the sound tech mentioned that when they have the amps on for the sound system, if they plug in any other equipment then unplug it, it makes a VERY loud pop. According to him, this was not a problem until after a large storm we had here two weeks ago (yes, we do get an occasional storm in San Francisco.

I checked it out and this does happen even if the thing being unplugged is not on the same panel as the AV equipment.

Any thoughts?
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It is not uncommon and i am a part time DJ.Really nothing to get concerned over.It is a spike and amplified you will hear it.Only solution is dedicated shileded outlet.MC or conduit unshared should fix it and conduit or mc must not be shared with anything.Yes costly.

They need seperate outlet for every piece (non shared neutral) to stop it.

You turn everything on and leave it on.Use the mute function on mixer
 
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sfav8r said:
yes, we do get an occasional storm in San Francisco.
Click to expand...

We're having one right now - it's been dumping all day.... When to the truck to get something and got SOAKED!

Anyway when you say unplugged to you power? Or AV cabling? Is there a chassis ground on the amp and connected equipment prior to the amp? If in a rack - is it grounded?
 
Jim W in Tampa said:
It is not uncommon and i am a part time DJ.Really nothing to get concerned over.It is a spike and amplified you will hear it.Only solution is dedicated shileded outlet.MC or conduit unshared should fix it and conduit or mc must not be shared with anything.Yes costly.

They need seperate outlet for every piece (non shared neutral) to stop it.

You turn everything on and leave it on.Use the mute function on mixer
Click to expand...

Thre are four circuits. Each is dedicated, run in conduit and thre are no shared neutrals. The panel that feeds these circuits is also on an isolation transformer.

I'm not sure about the grounding on the rack, I'll check that out.

This ob is extremely load. The problem is that when there is an equipment change of any kind during a show, thre is a huge pop that sends people covering their ears.

E57, I was referring to unplugging something from line voltage, not a mic or something...thanks for clarifying.
 
sfav8r said:
I was at a job today fixing a neutral-ground voltage problem (from a previous post). That problem is rectified,

I checked it out and this does happen even if the thing being unplugged is not on the same panel as the AV equipment.

Any thoughts?
Click to expand...

Your N-G bond - does it have an insulated GEC back to the main electrodes? See 250.30 If not you have a major ground loop, as the transformer you installed has current that is flowing all over the place.... This current will flow throughout the building, while it may be inpercievable as a readable voltage, that voltaage will vary greatly at different points at any ground location. The AV equipment is picking it up and amplifying the disconnection of that voltage IMO.
 
never mind... I was about to repeat a post I made earlier.... But maybe install a ground buss in the AV equipment area so that there is single point grounding for everything. All Insulated conductors to a single ground bar, and take that to the GEC.

So where are you working these days, is it a show I might see?
 
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Whats weird is it just started after the storm.Perhaps check/replace surge protector.Another poasability is the amp had a surpresser built in and it got fried.And i would be checking all neutrals and grounds in all the panels.Wish you luck and let us know what it ends up at being.Just fixed a friends club.He plugs in a kerosene heater that has a blower motor.Old one never caused a problem put the new one made a horrable noise in the system.Isolated problem by using 50 foot cord and plug into differant circuit.
 
Jim W in Tampa said:
Whats weird is it just started after the storm.Perhaps check/replace surge protector.Another poasability is the amp had a surpresser built in and it got fried.And i would be checking all neutrals and grounds in all the panels.Wish you luck and let us know what it ends up at being.Just fixed a friends club.He plugs in a kerosene heater that has a blower motor.Old one never caused a problem put the new one made a horrable noise in the system.Isolated problem by using 50 foot cord and plug into differant circuit.
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Its not really weird that it just started after a storm, but I understand what you are attempting to point out... something most likely changed as a result of the storm.

Troubleshooting 101: When the problem involves several pieces of equipment, attempt to isolate the problem to a specific piece.

First test I'd do would be to isolate the amplified portion of the system from the processing portion (i.e. the audio signal) then test for pops. If none, then the problem is narrowed to the preamp processing portion
 
Smart $ said:
Troubleshooting 101: When the problem involves several pieces of equipment, attempt to isolate the problem to a specific piece.
Click to expand...

More of the 101 class is that one should take customer ideas of how and when the problem started with a grain of salt. Storm probably has little to do with it. It's just a date they remember.
 
Jim W in Tampa said:
I do most of it from mp3 and use bpm with all the skins.Winamp for the quick find with f3
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I got the whole mixer dual cd setup, got tons of music with virtual dj on my computer, and even got a giant lighting system (i love lighting, i do it for the local theatre group) i do like 2 gigs a week
 
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