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Topic Title: "Noise" through music amplifiers
Topic Summary: Is it OK to disconnect the earth in 13 amp plug?
Created On: 29 March 2011 08:33 PM
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 29 March 2011 08:33 PM
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keithredpath

Posts: 424
Joined: 30 March 2002

A musician informs that he has disconnected all the earth wires inside the 13 amp plug tops for his equipment as this was the only way he could get rid of the "Noise" coming through his amplifiers.

Can someone explain where this noise comes from and how to get rid of it.

Also, would fitting RCDS without reconnecting all the earth wires make the installations safe?

-------------------------
keithredpath
 29 March 2011 08:38 PM
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AdrianWint

Posts: 262
Joined: 25 May 2006

NO, NO, NEVER EVER EVER!

Several musicians have died this way.

Disconnecting the mains earth is not the answer EVER.

The problem is an earth loop & the solution is to disconnect the screen on the audio cable which links the two pieces of equipment

Adrian
 29 March 2011 08:55 PM
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rocknroll

Posts: 8881
Joined: 03 October 2005

That fairly common and guitarists will never learn, but there are ways to eliminate 'earth noise' and they do all work, I have a 1U power conditioner with my guitar amp (only £70) and this works fine, the other way is fit a EMI power filter or what most experienced guitarits know if the noise is bad plug the signal lead into your pedal then to the amp, the noise only appears when you are playing and if not that bad is lost.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 29 March 2011 09:00 PM
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OMS

Posts: 19759
Joined: 23 March 2004

That fairly common and guitarists will never learn, but there are ways to eliminate 'earth noise' and they do all work,


LoL - says the man who used to run his fender from a flex pendant in the UMIST heating chamber

OMS

-------------------------
Failure is always an option
 29 March 2011 09:07 PM
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rocknroll

Posts: 8881
Joined: 03 October 2005

Originally posted by: OMS

That fairly common and guitarists will never learn, but there are ways to eliminate 'earth noise' and they do all work,


LoL - says the man who used to run his fender from a flex pendant in the UMIST heating chamber

OMS


LOL Guilty as charged. Never got any earth loop problems.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 29 March 2011 09:10 PM
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Zs

Posts: 2983
Joined: 20 July 2006

WOW! Do people like this still exist? Bonkers mad men.

Keith, let this thread run for a while then print it and show it to the musician.

I expect he needs a higher integrity earth. Easy, just make it all much thicker in terms of CSA and separate onto it's own TT if you can, with at least two stakes. I have had success with this in IT suites and music studios.

I imagine the 'noise' comes from other electrical equipment in use in the building and from the other musical equipment in use ( not music you understand). Earth leakage.

Give it somewhere to go with very low impedance, like a big fat line of green and yellow. Just like for Audio Buffs. There is loads of stuff on the web.

If you measure the earth leakage you will know a bit more about the RCD issue. If this is a commercial environment then you could get away without it. But if your musician friend is stupid enough to cut the earth out of his expensive equipment......Then I reckon an RCD might be, well, just a little bit of a good idea. Once you have put them back in maybe?

Sorry not a very technical explanation. I don't do technical in public. But it works. Happy and safe customers.

Even if nobody gets hurt without the earth in the plugs, that could be an expensive blow out of equipment.

Zs
 29 March 2011 09:20 PM
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potential

Posts: 1278
Joined: 01 February 2007

Originally posted by: AdrianWint

The problem is an earth loop & the solution is to disconnect the screen on the audio cable which links the two pieces of equipment
Adrian

I agree.
The problem used to be much worse with high impedance valve amps but it was always earth loops of one sort or another.
(except heater hum)
Microphone transformers were a godsend too.
 29 March 2011 09:21 PM
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John Peckham

Posts: 7523
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Disconnect the earth! Your having a tin bath me old mate!

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 29 March 2011 09:23 PM
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rocknroll

Posts: 8881
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Originally posted by: Zs

WOW! Do people like this still exist? Bonkers mad men.

Keith, let this thread run for a while then print it and show it to the musician.

I expect he needs a higher integrity earth. Easy, just make it all much thicker in terms of CSA and separate onto it's own TT if you can, with at least two stakes. I have had success with this in IT suites and music studios.

I imagine the 'noise' comes from other electrical equipment in use in the building and from the other musical equipment in use ( not music you understand). Earth leakage.

Give it somewhere to go with very low impedance, like a big fat line of green and yellow. Just like for Audio Buffs. There is loads of stuff on the web.

If you measure the earth leakage you will know a bit more about the RCD issue. If this is a commercial environment then you could get away without it. But if your musician friend is stupid enough to cut the earth out of his expensive equipment......Then I reckon an RCD might be, well, just a little bit of a good idea. Once you have put them back in maybe?

Sorry not a very technical explanation. I don't do technical in public. But it works. Happy and safe customers.

Even if nobody gets hurt without the earth in the plugs, that could be an expensive blow out of equipment.

Zs


Thats all fine if you are involved in the design of music venues and deal with this specialised subject, now to the real world, you have to remember most musicians play in pubs, clubs and hotel venues using the existing electrical installation so sometimes this does call for extreme measures, I am not condoning it but it happens, can you imagine running around with a loop tester, leakage tester doing a PIR when the well oiled punters are chomping at the bit waiting for a bit of rocknroll.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 29 March 2011 at 09:31 PM by rocknroll
 29 March 2011 09:30 PM
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Maxpower

Posts: 349
Joined: 15 February 2008

Aaaah yes, lifting the earths, takes me back...to my younger and stupider days...
 29 March 2011 09:41 PM
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AdrianWint

Posts: 262
Joined: 25 May 2006

Before I grew up & got a real job, I spent 15 years on the road specialising in power generation & distribution for rock'n'roll.

We used to meet this problem all the time. 99% of the time it can be eliminated by looking carefully at how the various elements are powered. Consider a typical pub gig...... kit on stage, plugged into sockets on stage, mixing desk at the back of the room plugged into the socket under the fag machine. Now consider what is happening... the kit on stage is connected to the earth of the local socket outlets but also linked to the mixing desk front of house by the screens on the audio cables. The desk itself if earthed via its 13A plug, maybe back to a different fuseboard and (hopefully) back to the MET where it joins the earth from the stage sockets - one big earth loop which leads to circulating currents which leads to "earth hum".

Several solutions are possible. a). Power the mixer from the same sockets as the stage kit (assuming that it doesnt overload things) hence reducing the size of the earth loop or b). Break the audio screens hence breaking the loop, or c). use audio isolation transformers to galvanically isolate the bits of kit.

simples!
 30 March 2011 12:25 AM
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sdjl

Posts: 18
Joined: 21 July 2010

We have a couple of isolation transformers on the tour I'm currently on. Mainly because a lot of the kit is from America, but it also helps the audio lot out. It helps they're on their own 200amp supply too.
 30 March 2011 07:22 AM
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gkenyon

Posts: 4478
Joined: 06 May 2002

Guitarists Beware

The strings of most electric guitars are earthed through the Amplifier. This is for two reasons:

1. helps to sink EM interference picked up by the guitar.

2. Stops "ticks" through amp when the fingers touch the screen, caused by static if the amp is double-insulated.


There are alternative methods of "grounding" the strings, but generally, it's just a solid connection to the shaft of the jack plug.


Removing the earth, makes it entirely possible that a guitarist will be directly exposed to "leakage currents" (protective conductor currents) from the amp, and any fault to the case (hence strings of guitar you're playing) won't be protected by the amp or circuit protective devices.

RCD may not help - shock current may well be huge, and you may be sweaty !!


As stated above, there are methods of stopping noise, and it's best to have your kit checked regularly for safety.

-------------------------
Eur Ing Graham Kenyon CEng MIET TechIOSH
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