Ground lifting, just how "dangerous" is it?

C

chava

New member
I am having a grounding noise problem with my motif ES Keyboard going into an apogee duet that just won't go away. I have tried different remedies and now I am considering what many consider the last resort; getting a three to two prong grounding adapter. I know many people use them (otherwise home depot would not carry them) but I just wanna know what risks I am taking and if it's worth it at all. Is any one on this forum using these adapters? Any pointers on how to stay safe?

Thanks.
 
chava said:
I am having a grounding noise problem with my motif ES Keyboard going into an apogee duet that just won't go away. I have tried different remedies and now I am considering what many consider the last resort; getting a three to two prong grounding adapter. I know many people use them (otherwise home depot would not carry them) but I just wanna know what risks I am taking and if it's worth it at all. Is any one on this forum using these adapters? Any pointers on how to stay safe?

Thanks.
Click to expand...

The ground is there for a reason ..... but heck we all live on the edge. ;)

I have to use a ground lift on my PC laptop power supply if I'm putting it into a PA for the same reason you may have to lift your equipment. Buzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz !!!

But most will tell you to never lift the ground.








:cool:
 
NEVER LIFT A POWER GROUND!!!

Look at those adapters. They all have a tab or short lead for connecting the third prong to a known good ground, usually the screw holding the wall plate on. If you don't know for a fact that the screw connects to a wall box that is properly grounded then don't do it. Doing this wrong can kill.

Instead, look at where things are plugged in. If you have gear plugged into different outlets on different circuits with different ground potentials then you need to change the way they are powered.

Also, look at your signal cabling. Is everything possible connected with balanced cables? Are you interfacing balanced and unbalanced equipment? Go read Rane Note 110.
 
bouldersoundguy said:
Also, look at your signal cabling. Is everything possible connected with balanced cables? Are you interfacing balanced and unbalanced equipment? Go read Rane Note 110.
Click to expand...

I was coming out of the motif on a balanced 1/4 inch but an apogee tech I spoke to recommended I use unbalanced 1/4 inch from the motif to XLR going into the duet (the outputs on the motif are unbalanced anyway).

Thanks for that link. Looks like a thorough write-up. Will get to it when I get home.
 
chava said:
I was coming out of the motif on a balanced 1/4 inch but an apogee tech I spoke to recommended I use unbalanced 1/4 inch from the motif to XLR going into the duet (the outputs on the motif are unbalanced anyway).

Thanks for that link. Looks like a thorough write-up. Will get to it when I get home.
Click to expand...

Also consider transformer isolation via direct boxes.
 
+1 for the Rane tech library. This is another useful resource: "Grounding and Shielding Audio Devices" http://www.rane.com/note151.html

There's also some great articles by Bill Whitlock on the Jensen web site. (The article on connecting unbalanced and balanced equipment describes how to modify unbalanced equipment to become balanced with the addition of as little as a resistor, capacitor and appropriate connector.)

References: http://www.jensen-transformers.com/apps_wp.html
and look for "Interconnection of Balanced and Unbalanced Equipment" and "Hum and Buzz in Unbalanced Interconnect Systems".

Paul
 
Just use one of these on the audio lines, also coverts balanced to unbalanced and unbalanced to balanced. Cheap as chips.

Solved all my computer ground loop problems both live and studio.

Alan.
 
Solid information so far...greatly appreciated. I have finally been able to trace the noise down to the USB connection between the motif and the computer. I get no noise at all through my audio cables from the motif to the duet interface. As soon as I plug the USB cable into any USB port on the computer I get noise. I get the noise even when the other end of the USB cable is not connected to anything.

What doesn't make sense to me is I have other devices connected to the computer via USB and I get no noise yet now I get noise just by plugging in a free cable on any port. Anyone have an idea what might be going on here?
 
Man, you dudes are paranoid. While recording is my hobby, I do professional live sound. We lift the ground all the time when there is no time left and the stage just won't stop humming.

I'd be shocked if you hurt anything/anybody.
 
Try unplugging your laptop and running on battery power.
My laptop gives off a lot of noise if it's plugged in which gets recorded.
If I unplug it I get silence.
Only happens when my laptop power cord has three prong plug. Never got any noise form the two prong plug (whihc I can't get from work anymore).
You have to watch the battery life though....
 
Chibi Nappa said:
Man, you dudes are paranoid. While recording is my hobby, I do professional live sound. We lift the ground all the time when there is no time left and the stage just won't stop humming.

I'd be shocked if you hurt anything/anybody.
Click to expand...

The simple fact is that lifting power ground can kill, and every time you do this you risk the lives of the people on stage. You can get away with it for years and then have one lethal incident.

Lifting signal ground is a whole different thing and should be safe. Direct boxes with transformer isolation and ground lifts are very useful.

I rarely have a problem with hum at my gigs. It used to be a problem when I ran the main and monitor mixes down the unbalanced returns of the snake. The first way I fixed that was to run power from the stage area to the mix position so it was on a circuit that shared grounding with other stuff on stage. Then I switched to balanced returns and can now often power the mix position with a local circuit with no hum.
 
Chibi Nappa said:
Man, you dudes are paranoid. While recording is my hobby, I do professional live sound. We lift the ground all the time when there is no time left and the stage just won't stop humming.

I'd be shocked if you hurt anything/anybody.
Click to expand...

Yes, you would get shocked and then hurt :p

For an appliance to use a two-prong plug it must be double insulated. A lot of laptop PSUs are for that reason. Some laptop USBs cause noise problems because they have crap internal grounding. No easy solution to that; even sometimes running on battery still causes digital or switching noise to leak into audio.

On the other hand, most modern pro audio gear has safety ground to chassis. If the gear develops a fault to chassis and the ground is lifted, you now have an energized chassis waiting to kill someone rather than a tripped fuse or breaker.

Isolate grounds on the audio signals with transformers rather than lifting power grounds. ART's 8 channel transformer DI box is what, $200? For that you would risk killing someone? I never heard a stage hum that an audio transformer couldn't fix. Unless maybe the venue's wiring is totally screwed, which would cause me to not work there.

No, death isn't common, but it's not unheard of either.
 
chava said:
Solid information so far...greatly appreciated. I have finally been able to trace the noise down to the USB connection between the motif and the computer. I get no noise at all through my audio cables from the motif to the duet interface. As soon as I plug the USB cable into any USB port on the computer I get noise. I get the noise even when the other end of the USB cable is not connected to anything.

What doesn't make sense to me is I have other devices connected to the computer via USB and I get no noise yet now I get noise just by plugging in a free cable on any port. Anyone have an idea what might be going on here?
Click to expand...

Do what I suggested previously and the problem will be gone. It is audio noise caused by a ground loop between the audio and the USB cables via the mains earth. You need 2 isolation boxes, 1 for the left / right in lines and one for the left / right out lines.

Cheers

alan.
 
witzendoz said:
You need 2 isolation boxes, 1 for the left / right in lines and one for the left / right out lines
Click to expand...

If I understood you correctly, I need to get two of these to cater to both the ins and outs on my interface, is that right? From the picture, I see the unit has two channels with two ins and two outs. Will I need a second unit in this case? I could be having this all screwed up in my mind, kindly assist.

Thanks.
 
chava said:
If I understood you correctly, I need to get two of these to cater to both the ins and outs on my interface, is that right? From the picture, I see the unit has two channels with two ins and two outs. Will I need a second unit in this case? I could be having this all screwed up in my mind, kindly assist.

Thanks.
Click to expand...

You need one unit on the lines to the apogee duet from the keyboard (or anything else you are pugging in), and another unit on the apogee duet outs going to the monitors. This setup means the apogee duet and the computer are completely audio earth lifted form other devices. If you are using microphones they are ok and don't need anything in between as the microphone is not connected to anything else.

If you have any problems after doing this there is something wrong with the unit or the keyboard.

Cheers

alan.
 
Chibi Nappa said:
Man, you dudes are paranoid. While recording is my hobby, I do professional live sound. We lift the ground all the time when there is no time left and the stage just won't stop humming.

I'd be shocked if you hurt anything/anybody.
Click to expand...
ditto on this.
Yeah, I know what the technically correct answer is but the truth is, I and most of my generation never worried about grounds at all and, in fact, many places we played didn't even have grounded outlets. Quite a few places probably still don't out on the bayous.
Hell, my house doesn't have grounded outlets.
And seriously, despite the fear that exists about this how many people have you ever heard of getting hurt by this?
I've heard of only a couple and I'm sure there must be a couple more but out of literally millions and millions of instances where someone lifted the ground to have only a dozen or two actually harmed makes it one of the safest things you can do statistically.
I'm NOT saying that you shouldn't try to be grounded but I just can't imagine anyone getting hurt by lifting a ground on a keyboard.

And BTW ...... getting a mild shock if your lips touch the mic doesn't qualify as getting hurt. It's not pleasant but it's not gonna kill you.
Harmed would be when I got 110v thru my lips to the mic! :eek:
Now THAT was unpleasant. :D
But it had nothing to do with grounding.
 
Lt. Bob, the chances of getting this kind of injury are low, but it's so easy to prevent that not bothering to take the appropriate precautions is reckless. Deliberately lifting power ground is simply not necessary when there are better ways of getting rid of hum. Use transformers, lift a signal ground, run power from circuits with no ground potential between them. Even using one of those 2-prong adapters correctly, grounding the lug, is okay if you know you're actually grounding it.
 
moresound said:
Lt. is an old timer where 110 doesn't bother him much :eek: just a little tickle! ;)








:cool:
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haha ..... well, when it came thru my lips it was a bit more than a tickle! :eek:

It was more like someone hit me in the face with a bat! I remember it well ...... blue fire and I was on the floor! LOL

The power switch to the Ampeg SVT had gotten slammed during moving and the hot lead made contact with the amps' chassis sending 110 to my bass. Hell, after I got up I touched the large E string to the mic stand like you do to check for grounding issues and *POW* .... the string was immediately burned thru!
:D

Getting bit by 110v in a hand or something doesn't freak me out too much but the lips ........ I'm gonna say avoid that.

:)
 
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