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Clean Earth sockets

IronFreely
I’m just wondering about how clean earth sockets (Some of you may call these high integrity sockets) fit into the requirements of BS7671 in terms of their use in domestic homes.


One of my clients has asked me to look into the use of some clean earth sockets to be used to power audio equipment in their home studio, the basic idea is that a completely separate Earth helps eliminate what’s known as an earth hum on audio equipment caused by functional earth leakage of other equipment connected to the same circuit and disturbances originating from the suppliers earthing arrangement. The basic concept seems to be to insulate the cpc from the earth terminal of the socket outlet which then has its own independent Earth electrode, high integrity sockets seem designed to accept and insulate a cpc and a separate earth. 


My concern is that this sort of thing is usually used in a restricted access environment where only IT or audio engineers are going to be around and might be considered trained and competent to understand the risk of introducing an earth potential to the equipotential zone that is not in itself connected to the equipotential bonding. It wouldn’t be a problem if I could guarantee restricted access or that the socket would only supply class 2 equipment, but as this is a home studio it seems a bad idea to have an earthed metal casing of some piece of audio equipment that may be completely separate from all other earthing and bonding in the property? 


id appreciate your thoughts and advice please, I’m confident a separate clean earth will resolve the earth hum problem which I’ve seen work well in theatres (essentially restricted access) before but never in a domestic property.


Edit: I should add that the property is a TT property but because the street is a hodgepodge of TNS and TNCS (I have other neighbouring clients really close by) you should assume the gas and water pipe are throwing in a bit of PME related disturbance.
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    IronFreely:

    Chris I’m sure they have an earth hum, I can hear it, the client can hear it, the clients band mates can hear it, we can all hear it when the equipment is on, we can all tell it goes away when the equipment is off, we can all hear it on recordings made with this equipment, we can hear it has been significantly reduced when plugged into the power supply in my shed which is a TT island, a group of people with something like 300 years of collective experience in music and sound engineering do not need to measure a sound to know they can hear it nor do they need to measure it’s absence to know it’s been eliminated by driving across town and plugging it in elsewhere.


    Thank you for sharing this new piece of information.


    I am trying to approach this scientifically. So my next question is what makes you think that the installation's earthing arrangement is at fault?


    I might get drummed out of here for suggesting it, but what happens if the earth is disconnected? Does the hum go away? That may sound like a reckless approach, but if you switch on so that you can hear the hum, then isolate remotely, disconnect the earth, and then re-energize ensuring that everybody stands well back and understands the risks, it ought to be safe.


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    IronFreely:

    Chris I’m sure they have an earth hum, I can hear it, the client can hear it, the clients band mates can hear it, we can all hear it when the equipment is on, we can all tell it goes away when the equipment is off, we can all hear it on recordings made with this equipment, we can hear it has been significantly reduced when plugged into the power supply in my shed which is a TT island, a group of people with something like 300 years of collective experience in music and sound engineering do not need to measure a sound to know they can hear it nor do they need to measure it’s absence to know it’s been eliminated by driving across town and plugging it in elsewhere.


    Thank you for sharing this new piece of information.


    I am trying to approach this scientifically. So my next question is what makes you think that the installation's earthing arrangement is at fault?


    I might get drummed out of here for suggesting it, but what happens if the earth is disconnected? Does the hum go away? That may sound like a reckless approach, but if you switch on so that you can hear the hum, then isolate remotely, disconnect the earth, and then re-energize ensuring that everybody stands well back and understands the risks, it ought to be safe.


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