I would hope the GFIC on a grounded amp would save you from a deadly shot from a hot mic anyway.
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Ground lift
- Thread starter David Jayne
- Start date
Oh my goodness. Okay, once again ~
SERIOUSLY - "NEVER" REMOVE OR LIFT THE GROUNDING PLUG (SAFETY GROUND) ON THE AC POWER CORD - PERIOD!!!
- Feb 12, 2006
- 60,961
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- 220,645
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
You are just trading the crapshoot probability of one fault over another. If the bass amp has a fault and the mic is grounded, you will receive a shock, but if there is a fault in the PA (mixer, or anything else if ungrounded) and the bass amp is grounded you will also get a shock. If everything is grounded you can not receive a shock since no chassis or housing can rise more than a few volts above ground.
+1. ^^^ This.
Okay, I sure hope so.
Here's a thought - just hire a union shop (journeyman) sound company, that way everything will be properly connected and grounded, including the backline AC power which needs to be on the same circuit as monitoring and FOH.
Joe, as much as I'd love to do that, my gigs can't afford it.
I agree-pulling the ground is a really risky thing. I'm not doing it and wouldn't advise anyone to do so. My goal here is simply to get expert opinion about my proposed solution. I'm just spit-balling here. That's it.
Gotta love 240v, far too dangerous to mess with substandard wiring so it tends to be fine. I think your 110v is a little too easy to survive, breeding poor behaviour. Afaik there is no such thing as an outlet tester here.
Occasionally my pedals pick up noise from compressors and blenders but I never heard of bad power at a venue.
Occasionally my pedals pick up noise from compressors and blenders but I never heard of bad power at a venue.
Excellent - but the word is "dangerous".
OP, its not a solution - its a potential problem. The solution is to make sure everything is properly grounded. And my goal here, is to make sure everyone really understands removing or lifting the safety ground is dangerous!!!
Also keep noisy things like dimmers, motors, pumps, and etc on separate circuits.
Which is impossible. There are many, many times we walk into clubs with house PA systems, festivals etc. where we have absolutely no control. Having your amp grounded is both your friend and enemy. More often, it's your enemy whether you care to admit it or not. Hot mic is far, FAR more likely than hot amp, in my 25 years of doing this.
My goal is to find a safe solution to this dilemma.
Oh my goodness - not again.
Hmm, it really is a shame that some people just refuse to believe manufacture warnings.The safest solution to YOUR dilemma is to buy an AC power outlet checker http://www.amazon.com/Electrical-Re...d=1384875888&sr=8-2&keywords=AC+outlet+tester, and test outlets - and if the AC outlet isn't properly wired and grounded Don't plug into bad AC outlets and refuse to play/work until the problem is fixed.
"NEVER" REMOVE OR LIFT THE GROUNDING PLUG (SAFETY GROUND) ON THE AC POWER CORD - PERIOD!!!
EDIT: EDIT:
Wow, I missed this ~TIP: If the electrical isn’t up to code, report the venue to authorities - and stop putting your life in the hands of a messed up drug addict.
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- Feb 12, 2006
- 60,961
- 5
- 220,645
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
IME, PA equipment is much more often properly grounded and bonded because PA gear is more often used in installation markets which adhere to safety regulations much more closely than MI gear (though this has been improving greatly too over the last 10 years)
Regardless, solid grounding of the safety ground is the proper thing to do, and if something were to happen, a lifted safety ground would be immediately suspect and likely expose you to liability because it's an intentional act. Also, if you are indeed a an engineer, you may be held to a higher standard since you are presumed to know that the equipment ground is an essential component of the safety system.
Regardless, solid grounding of the safety ground is the proper thing to do, and if something were to happen, a lifted safety ground would be immediately suspect and likely expose you to liability because it's an intentional act. Also, if you are indeed a an engineer, you may be held to a higher standard since you are presumed to know that the equipment ground is an essential component of the safety system.
This was an interesting read. Thanks for the link.
One thing I found interesting is that this paper explains how a ground lift on a balanced signal (such as an XLR cable) should only be done at the receiver side, if it is done at all. The driver side should never be lifted to properly reduce noise. Yet his is exactly the opposite of what you find in most audio applications, where it is the driving DI that has the lift switch and the receiving mixer is always grounded.
I read it thoroughly last night and I think the reasoning is sound (yuk yuk) on balanced line ground lifts with respect to noise pickup. Practically speaking, it's more sensible for DIs to have a ground lift switch than for every channel on the desk to have one or for the crew to use pin one lifted XLR adaptors at the console end. It's a bit of a tradeoff but generally noise from a ground loop is going to be worse than the effects of a somewhat compromised CMRR.
As for AC ground lifts, my advice would be to not do it. For one, if you've lifted AC ground on one of your devices and someone gets a shock, you're liable. My experience is that these days, where everything has the safety ground, situations where mics or amp chassis are energized are limited to fault conditions and they don't really happen all that often. Good reason to check outlets and/or equipment in places that look a bit dodgy. Not like in the old days when amps didn't have the dedicated ground and had a polarity switch so you could in fact, easily energize the chassis and you generally found out whether the switch was in the right position or not by trying it...
If your amp is connected to a GFCI, the device will protect you from a fault in YOUR AMP ONLY, and NOT FROM ANY OTHER equipment.
So, if the hot mic is not connected to your amp, and there is a path to ground through your body, you will receive a shock. Your GFCI protected amp will not prevent it.
Depends if you're standing barefoot in a puddle of water or not.
I see what you're getting at here. If you use a GFCI and lift the safety ground on your amp, a hot mic will not have a path to ground through your bass/amp and the GFCI will trip if your amp chassis goes live and you touch anything that has a path to ground like a grounded mic.
I don't see anything wrong with this reasoning other than the potential liability ramifications of lifting the safety ground. Disclaimer: I am not advising you to do this.
Let me put it to you this way - if I was in charge (reasonable and liable) I'd TELL YOU to get your ungrounded **** off of my stage!!!
BTW: You say you're an engineer? What is your name and the name of the venue? Thanks
Depends if you're standing barefoot in a puddle of water or not.
I see what you're getting at here. If you use a GFCI and lift the safety ground on your amp, a hot mic will not have a path to ground through your bass/amp and the GFCI will trip if your amp chassis goes live and you touch anything that has a path to ground like a grounded mic.
I don't see anything wrong with this reasoning other than the potential liability ramifications of lifting the safety ground. Disclaimer: I am not advising you to do this.
Exactly my reasoning, but I'm not absolutely sure the GFCI would trip in the case of hot mic or otherwise. Actually I can't think of a reason it would.
Joe-I'm an industrial engineer, not audio.
It definitely won't trip in the case of a hot mic but lifting the safety ground on the amp would remove that path to ground so you wouldn't get a shock unless you were standing barefoot on a concrete and/or wet floor. With the amp's safety ground lifted the GFCI will only trip if there is a fault in your amp that energizes the chassis and you come into contact with a path to ground (assuming enough current flows through you to trip it).
