A portable ground fault circuit interrupter, connected in line, before your equipment will provide a little added protection from faulty premises wiring. It does not need a grounded circuit to function, and could save you from a painful shock, or death by electrocution.
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Ground lift
- Thread starter David Jayne
- Start date
The grounded plug came to amplifiers the same time it came to everything else. It wasn't in response to musicians more than anyone else getting electrocuted. Is it safer than the old ungrounded plug? Of course it is.
- Feb 12, 2006
- 60,953
- 5
- 220,612
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Frankly, it's scary that anybody these days would think it's ok lifting the safety ground from an amplifier or any other product for that matter. Solidly grounded chassis are used to guarantee that any electrical fault to exposed metal chassiswork is safely shunted back to the source AND that the voltage on the exposed chassis parts does not raise above ground while the fault clears.
The ground lift associated with a direct out involves lifting the circuit ground which is entirely different. This prevents currents from circulating on the audio ground between 2 pieces of equipment that have slightly different ground potentials and inducing hum into the audio circuitry.
The circuit grounds are not rated to handle the fault current of an electrical fault, the currents will detroy the signal ground path including the snake line, and the pcb ground traces at either or both ends of the snake. Every once in a while we would see something like this on an expensive console where a fault and an AC safety ground lift combined to take out say an input module or a ground path on an A/D converter board. Suddenly the fault turns into a multi-thousand dollar repair.
A properly designed DI on a bass amp can be just as quiet as the best stand alone DI boxes. There is no reason at all why they can't be quiet and work well under almost every condition. Poorly designed DI circuits, especially those not designed with the real world in mind certainly can have problems though.
The ground lift associated with a direct out involves lifting the circuit ground which is entirely different. This prevents currents from circulating on the audio ground between 2 pieces of equipment that have slightly different ground potentials and inducing hum into the audio circuitry.
The circuit grounds are not rated to handle the fault current of an electrical fault, the currents will detroy the signal ground path including the snake line, and the pcb ground traces at either or both ends of the snake. Every once in a while we would see something like this on an expensive console where a fault and an AC safety ground lift combined to take out say an input module or a ground path on an A/D converter board. Suddenly the fault turns into a multi-thousand dollar repair.
A properly designed DI on a bass amp can be just as quiet as the best stand alone DI boxes. There is no reason at all why they can't be quiet and work well under almost every condition. Poorly designed DI circuits, especially those not designed with the real world in mind certainly can have problems though.
I figured as much. Even as he assured me I thought "no way the board is gonna shunt 15 amps to ground (without even knowing about the possible resistor on the ground pin) through its audio circuits. It will simply blow up and the current will continue to flow." I'm no EE but I'm a tech and I know better.
But I thought, "this kind of dangerous failure is extremely unlikely" so I went with it. This guy used to for many years run FOH for a large, well-known sound company that does large, professional concerts. I said "hell, its alright. This time."
So there you go. Lesson learned. Thanks fellas. Dave.
+1
everybody wants to whip out the AC ground lift plug but nobody thinks to use a far safer ground lift XLR cable (pin 1 lift) instead.
Let me add that connecting your equipment to a GFCI will only protect you from a ground fault in your own amp. It will not protect you from any other equipment, (like a microphone, connected to the FOH) you may come in contact with.
Right - and that still doesn't change the fact that you gave bad advice... It is a very bad idea to trivialize the act of bypassing an amp's power ground, period...
- georgestrings
I gave no advice; I speak only for myself and my opinions are my own. You may disagree and that's fine. I have been playing with amps and electric instruments for nearly 50 years and I'm not dead yet, and my first four or five amps had no ground pins.
I give no advice. I believe that everyone should do only what they are comfortable with. Kids, don't try this at home.
- Feb 12, 2006
- 60,953
- 5
- 220,612
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Amplifiers now have solidly grounded chassis with 3 pin AC connectors because of the number of injuries, and to reduce the risk of future injuries.
Ungrounded amplifiers can be built these days, but the AC isolation standards are much different than grounded chassis as well as ungrounded legacy equipment.
Ungrounded amplifiers can be built these days, but the AC isolation standards are much different than grounded chassis as well as ungrounded legacy equipment.
+100%.
Yeah, I know huh - its very scary. People need to read the manuals and believe the manufactures warning them never to operate without the safety ground.
- Feb 12, 2006
- 60,953
- 5
- 220,612
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
+100%.
Yeah, I know huh - its very scary. People need to read the manuals and believe the manufactures warning them never to operate without the safety ground.
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?
- Feb 12, 2006
- 60,953
- 5
- 220,612
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Yeah it does. And I think he was only 20 something years old when he was electrocuted back in the 70s too.
This goes against everything I've been told about electronics. If it's true it also makes the AC ground plug pointless. So I'm pretty sure you're mistaken there.
I have one of those. Doesn't do ****. I still get ground loops, and have to use an external DI. Stupid Ampeg not providing a ground lift on the built in DI on the SVT4PRO.
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There is no problem to lift the ground on the XLR - it is still grounded on the mixer side, In fact that is how audio connections are SUPPOSED to be made - grounded ONLY on one side to prevent ground loops! It's the way we wired many studio and PA racks. All cables grounded at one end only, and all the gear star grounded to a central point. Voila - no ground loops! Even my home stereo rack is wired that way.
Also - I am pretty sure that a GFCI has to be grounded to work - it senses current leakage to ground.
Also - I am pretty sure that a GFCI has to be grounded to work - it senses current leakage to ground.
