Ground Lift ?

[richy316]

On the back of my Warwick Pro Fet 4 just above the power socket, well i'm not really sure what it supposed to do?

I've read the manual but that does'nt really help in the slightest, so i'm putting it out to you wise folk to give me some expert knowledge on this?

[Bill Fitzmaurice]

[quote name='richy316' post='206534' date='May 26 2008, 08:13 AM']On the back of my Warwick Pro Fet 4 just above the power socket, well i'm not really sure what it supposed to do?

I've read the manual but that does'nt really help in the slightest, so i'm putting it out to you wise folk to give me some expert knowledge on this?[/quote]
It's used to prevent ground looping.
[url="http://www.rane.com/note110.html"]http://www.rane.com/note110.html[/url]

[warwickhunt]

When the amp is in use by itself you're unlikely to ever need to use the button. It is mainly useful when you have a couple of units linked together in a rack etc. and in the event you are getting an earth humm, try pressing the button. Loads of amps have them though I've not had reason to employ the Ground Lift on any of my amps in the last 25 years.

So long as you know it's there and what it does, then just forget about it.

[bnt]

A plainer English version of what that Rane document says about multiple paths to ground causing ground loops:

A common cause of ground loops in a studio setting is having two bits of mains-powered gear, connected together in the audio path, that have different mains earths. "Different" in this context means e.g. one bit plugged in on one side of the room, the other bit getting power from the other side of the room, or more subtle problems like grounding to a rack. You can sometimes get mains current flowing between them along the [i]audio[/i] ground, because the mains earths on the two sides of the room are not equally-well earthed. (Sometimes, Earth... isn't!)

In a live situation, you probably won't have that problem, and you would not want to lift ground anyway, for safety reasons. If you were sending a signal to the PA, it would be a balanced signal that wouldn't cause a ground loop.

[clagooey]

[quote name='Bill Fitzmaurice' post='206586' date='May 26 2008, 03:05 PM']It's used to prevent ground looping.
[url="http://www.rane.com/note110.html"]http://www.rane.com/note110.html[/url][/quote]

...

That link looks really interesting. And I'm sure some day I'll get around to reading it properly. However, in my current fatigued state, trying to read that has pretty much melted my conscious. My head physically hurts now.

...

I think I'm gonna go lie down for a while..

[Bill Fitzmaurice]

[quote name='clagooey' post='206694' date='May 26 2008, 12:49 PM']...

That link looks really interesting. And I'm sure some day I'll get around to reading it properly. However, in my current fatigued state, trying to read that has pretty much melted my conscious. My head physically hurts now.

...

I think I'm gonna go lie down for a while..[/quote]
If you're a professional musician/soundman/DJ/whatever who makes his living with electronic sound reproduction devices all of the RaneNotes are required reading, and should be downloaded and kept for reference. The knowledge base therein is the equivalent of an associates degree in audio engineering.

[ironside1966]

+1
This is a good simple answer.


[quote name='warwickhunt' post='206618' date='May 26 2008, 04:03 PM']When the amp is in use by itself you're unlikely to ever need to use the button. It is mainly useful when you have a couple of units linked together in a rack etc. and in the event you are getting an earth humm, try pressing the button. Loads of amps have them though I've not had reason to employ the Ground Lift on any of my amps in the last 25 years.

So long as you know it's there and what it does, then just forget about it.[/quote]



It is a safe alternative to removing the earth wire from a plug.

[wateroftyne]

[quote name='Bill Fitzmaurice' post='206714' date='May 26 2008, 06:20 PM']If you're a professional musician/soundman/DJ/whatever who makes his living with electronic sound reproduction devices all of the RaneNotes are required reading, and should be downloaded and kept for reference. The knowledge base therein is the equivalent of an associates degree in audio engineering.[/quote]

Wow. Really?

I'll get round to that... sometime. But right now, I have to go and do stuff...

[richy316]

Thanks for clearing that up guys i think i get the basic "when its needed and when it isn't idea" mucho gracias

[rmorris]

[quote name='bnt' post='206621' date='May 26 2008, 04:10 PM']A plainer English version of what that Rane document says about multiple paths to ground causing ground loops:

A common cause of ground loops in a studio setting is having two bits of mains-powered gear, connected together in the audio path, that have different mains earths. "Different" in this context means e.g. one bit plugged in on one side of the room, the other bit getting power from the other side of the room, or more subtle problems like grounding to a rack. You can sometimes get mains current flowing between them along the [i]audio[/i] ground, because the mains earths on the two sides of the room are not equally-well earthed. (Sometimes, Earth... isn't!)

In a live situation, you probably won't have that problem, and you would not want to lift ground anyway, for safety reasons. If you were sending a signal to the PA, it would be a balanced signal that wouldn't cause a ground loop.[/quote]

yes - the RANE notes are really good. Also look up the technical notes etc. from JENSEN transformers for more about grounding / balancing / earthing etc.

re: and you would not want to lift ground anyway, for safety reasons.

it shouldn't be a safety issue to use the ground lift switch on the amp.
Unlike removing the yellow/green earth wire in the plug , with the switch the chassis metalwork etc remains 'earthed' but the signal 0V ( 'ground' ) is disconnected from earth, or more usually connected to it via a resistor of around 100ohm.
The resistor prevents the earth and 0V voltages drifting too far apart and exceeding the common mode range but should be enough to 'break' the earth loop.

Ground lift can be a bit hit and miss - in fact I think that on one Rane tech note the question is asked : 'When did a groud lift [u]really [/u]make things better!' or something along those lines.

AND NEVER REMOVE THE MAINS EARTH !!!!

[peted]

My rule is - leave the Ground Lift 'off'. If the sound engineer says that he is getting a 'hum' or noise from the DI socket in your amp, then switch the Ground Lift 'on' (preferably after the engineer has muted the line from your amp).