Ground lift adapters

famous beagle

Well-known member
Ok, I know that using a ground lift adapter is very dangerous and presents a shock hazzard in the event of equipment failure (or several other scenarios).

My question is this:

If they're so dangerous, what is their purpose?
 
To allow the use of gear equipped with 3-prong plugs into 2-prong sockets.

Ok, I guess I never fully understood the whole grounded thing then. If two-prong sockets don't have a ground, they shouldn't be used (for musical equipement anyway) for safety reasons ... correct?
 
Some gear doesn't need a ground. Households in the US operated for many years with only two wires, but modern practice requires a separate ground. It's where the old and the new meet that adapters are needed.
 
Some gear doesn't need a ground. Households in the US operated for many years with only two wires, but modern practice requires a separate ground. It's where the old and the new meet that adapters are needed.

Thanks. By the way, where in East Texas? I was born in Beaumont and grew up in Houston. Moved to Denton in 1990 for UNT and finally left the state (to Milwaukee) for good two years ago. The summers were finally too much for me!
 
some bad info here i think so perhaps this will help.... a two wire cord has a ground??? yes it does... one wire is the ground the other is hot... there has to be a ground to reference to !!! no ground?? no voltage... the third wire is a safety... it's purpose is to carry the extra voltage to ground quickly in the event of an extreme failure.... the purpose of a ground lift is to get you through the job without tracing the problem which is the correct course of action... but you'll be better able to do that when the clients gone... IMO...
 
some bad info here i think so perhaps this will help.... a two wire cord has a ground??? yes it does... one wire is the ground the other is hot... there has to be a ground to reference to !!! no ground?? no voltage... the third wire is a safety... it's purpose is to carry the extra voltage to ground quickly in the event of an extreme failure.... the purpose of a ground lift is to get you through the job without tracing the problem which is the correct course of action... but you'll be better able to do that when the clients gone... IMO...

Thanks for the input demented. I think we're confusing terminology here. I was under the impression that, in a 3-prong system, the hot wire (usually the small flat prong) is called the "hot" or "live" wire, the return (the bigger flat prong) was called the "neutral," and the grounding connection (the round prong) is called "ground" or "earth."

I understand that usually current does not flow through the grounding connection (the round prong), and that it's there in case something shorts in your equipment, placing high voltages on enclosures, mics, etc. When that happens, the grounding connection steps in and provides a safe "backup" place for the current to return to ground.

But I think your last comment answered my question. Though I think you're talking about in the recording environment (I actually had gigging with an amp in mind, but since this is the HR board, your thinking makes perfect sense), the principle's the same. It's not safe, but it is a quick fix.

So ... if a venue doesn't have a 3-prong outlet (I don't know if there are any like this anymore, or maybe someone's handing you a power strip to plug into with only two-prong receptacles), are you basically just screwed out of being safe?
 
So ... if a venue doesn't have a 3-prong outlet (I don't know if there are any like this anymore, or maybe someone's handing you a power strip to plug into with only two-prong receptacles), are you basically just screwed out of being safe?

yep that's it....


as to the rest... i think the problem comes in as people have a tendency to expect "neutral" to some how be different... it really is your "Active" ground for lack of better term... also a minor quibble with my other post... it really is the current that drains away not the voltage... it's a strange differentiation since ya cant have current without voltage and without a sustained current source the voltage collapses... but it is the current that kills and/or does the work not the voltage.... i can killya with 12V given enough current (and applied in a particularly demented way)
 
Get one of those 3 prong outlet testers with the L.E.D.'s. Ocasionally some idiot will have wires reversed in an outlet. You'll see this with bar and club owners trying to save a buck. I got the shit shocked out of me with a bad outlet one time. We checked it afterwards and the grnd. and neutral were reversed. It was the only outlet on the stage that was like this,(figures).
 
Also, that little U-shaped tab at the base of the 'ground-lift' adapters is actually to make the ground connection. Screwing the tab under the receptacle cover plate screw between the outlets, might actually get you a real ground. This depends on two major things:
-That there is a ground wire coming to the receptacle box at all
-That the box is installed properly (flush with the wall surface) so that the mounted outlet's frame, which includes the cover plate screw, makes electrical contact with the box, i.e. ground.

Not surprisingly, I've encountered very few 2-pronged outlets like this... But as suggested above, a $3 tester will help you at least get the polarity right and let you know if there is a ground connection to be had. Finally, you can correct the polarity of a 3 or 2-pronged outlet with a 'ground-lift' adapter by facing the tab towards the plat cover screw and using the side of the outlet that makes the polarity correct (as indicated by the tester). And in a 3-pronged outlet, if you screw the tab under the cover screw, you will have a ground.
 
Two more things:
A tip I figured out with my old Ampeg tube amps for checking the polarity without a tester, especially if you have a polarity switch and a 2-pronged power cord. This is to prevent electrical shocks when touching other equipment.

Plug a patch cable into the amp leaving the other end disconnected from anything. Turn the amp on and turn the volume up a fair amount. Try the polarity switch in both positions - the good position is the quieter of the two. You may have to touch the tip of the patch cord, but I found without touching it and with turning the volume up to around 75% the difference between the two positions was clearly evident.

2nd:
Neutral vs. ground - US code says that the neutral must be tied to ground at the service entrance, so as dementedchord said, the ground is your redundant, safety path.
 
I believe this is called a "bonded neutral". I just went through this with my portable generator. The neutral is tied to the ground.
 
It's a Chinese conspiracy to knock you on your ass from the other side of the world.
 
I know this is old but peole can still google and come up with this thread.

Ground lift is a term used to cover a variety of methods to help isolate ground loop noise between and in audio systems (Direct Injection {DI} and mixers are more prone to this. This can be jerry rigged or come as a factory istalled feature on eqipment. It has nothing to do with the third prong on an A/C outlet or plug. You should never disconnect these.

Here is a good explination by prosigna on acapella.harmony-central.com:

The DI on your amp has 3 pins. Pin 1 is the ground, pins 2 and 3 carry the signal in opposite phases from each other. Pin 1 connects the ground from your amp to the ground on the console. Sometimes this causes noise. The ground lift switch disconnects Pin 1 (sometimes refered to as a Pin 1 lift) so all that is connected to the console is pins 2 and 3.

This is very different than an AC ground lift. That is where you remove the ground wire from your amp to the power outlet. Some people carry a little adapter to do this, others just yank out the 3rd prong from their plug. DON'T EVER DO EITHER. If anyone tells you this is safe they are wrong. The AC ground protects you from being killed. The pin 1 ground is part of the noise shielding and not a safety feature so there is no danger in lifting it from your amp.

Lifting pin 1 from a microphone is dangerous, don't do that. The only ground the mic has is the pin 1 ground. In the case of a microphone it is a safety feature. Your amp and your bass are grounded by the power plug so the pin 1 ground is not needed.
 
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