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Ground lift

#63
Evening time over here.

I'm no electrical genius so I avoid shooting my mouth off in life or death threads until someone like yourself shows up. Thanks for being around. I get to bounce concepts to confirm what I remember from high school physics classes many years ago.
 
#65
Great timing to find this thread. I had problems at a venue I had never set up our equipment at before this weekend. We were getting shocked by the microphones, had buzzing coming from the DI output of my SWR amp, lot's of issues. I read through most of the links and post here. Did a little more research on line this morning and found an article that seems to be on point, from MIT.

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I am still studying through this, hope it may help the subject. I will be better prepared for the next encounter.
 
#66
The DI out on my amp has a ground lift built in. I still on occassion run into a soundguy who tells me under no certain terms will they run a line directly into my amp. So my response if fine, I will just turn my amp up to cover his lack of PA. The band usually gives me sneers for that one, but I know my amp and it does not have a ground hum. Bad incoming power and too much crap on the same circut is usually the culprit.
 
#67
scottbass said:
This is NOT my experience. Any time my amp has been on a 2-wire circuit (correct polarity but no ground) and the PA is on a different 2-wire circuit (again, correct polarity but no ground) I have gotten the notorious blue flame of death when my lips get near my SM58. I immediately stop singing backing vocals until someone does something about it. I have also begun carrying my own circuit tester as others have mentioned in previous posts. I don't consider this "over the top hysteria." :rollno:
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That's more because there's NO ground. If your bass is grounded through your DI, you won't get this.
 
#71
Oh no, here we go again. :(
TBers, please read your manuals and believe the manufacture warnings. Thanks

spitmilkfunny.gif
 
#74
dmusic148 said:
+1. Sadly, having a ground makes it worse. This is why I'm interested in possibly trying the GFCI + no AC ground approach.
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:rollno::rollno: NO - DON'T REMOVE OR LIFT THE SAFETY GROUND!!! :rollno::rollno:

agedhorse said:
Certainly saves them from embarrassing moments in the E.R. when asked how they got electrocuted... can you say "I was a dumbass" and leve it at that?
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+1.

But unfortunately it seems some people just refuse to believe warnings. Oh well. :(
 
#76
Downunderwonder said:
What say a paperclip drops in your amp, you hit a note and it wobbles the stage just the wrong way and 400v hits the chassis just as you step up to the mic? My fear is no GFIC will save you if the mains chassis ground has been lifted.
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P Town said:
I believe you are correct.

You will be doing the "KiloWatt Shuffle" on stage.

The audience will think its part of the act.

Look at it this way. Being a musician is still safer than farming.
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Safety is nebulous. Those who perish had a lack of safety but stayed safe until their luck ran out.

Aged Horse didn't challenge my post. I take it my concern is valid. A little knowledge is a dangerous thing.
 
#79
Downunderwonder said:
Man this mulberry bush needs some attack goats set on it.

You lift your chassis earth, you risk a life ending zap off your amp, GFIC or not.
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Maybe-I need to look further into GFCI function to be sure, but the other thing lifting AC ground does is virtually ELIMINATE the chance of getting spanked by a hot mic, which is just as dangerous. Which scenario is more likely to occur? Hot bass amp chassis, or hot mic? It's worth thinking about.
 

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