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Clean Earth sockets

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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0 Stewart Ross over 4 years ago

In a home studio it can be difficult to eliminate all sources of noise which affect audio signals. The OP can hear mains hum, and eliminating it can be difficult, as gkenyon‍ has pointed out. The difference between a 'clean' source and one that is noisy is often subtle, but you know it when you hear it and it isn't about measurements of signal to noise ratio or the like at all.

Balanced inputs (where there are two signal leads, one a send and the other a return, with a separate screen connection) are less prone to such problems, but unbalanced inputs (single signal send and common screen/signal return) from guitars and other instruments can be a problem. Signal levels from mics and guitar pickups are very low (in the mV range) so even what might be thought of as very low induced hum levels will be decidedly audible and very distracting, and potentially ruining from a recording point of view. As the OP has said, he doesn't have to measure it as he can hear it directly.

There are articles dating back a long time on the abolition of ground loop effects - for instance http://www.muzines.co.uk/articles/studio-earthing-techniques/4139

My brother has a home studio, and I maintain the equipment he uses. In one case he recorded a number of lead vocals using a brand-new balanced mic cable which unknown to him was defective leading to a very low level of background hiss, occasional clicks and distortions on the recordings. No amount of 'masking' by overlaying the instruments in the mix could overcome the defects in the vocals he recorded with the duff lead, which he had to redo once the duff lead was replaced.

Good luck in eliminating the problem.
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0 Stewart Ross over 4 years ago

In a home studio it can be difficult to eliminate all sources of noise which affect audio signals. The OP can hear mains hum, and eliminating it can be difficult, as gkenyon‍ has pointed out. The difference between a 'clean' source and one that is noisy is often subtle, but you know it when you hear it and it isn't about measurements of signal to noise ratio or the like at all.

Balanced inputs (where there are two signal leads, one a send and the other a return, with a separate screen connection) are less prone to such problems, but unbalanced inputs (single signal send and common screen/signal return) from guitars and other instruments can be a problem. Signal levels from mics and guitar pickups are very low (in the mV range) so even what might be thought of as very low induced hum levels will be decidedly audible and very distracting, and potentially ruining from a recording point of view. As the OP has said, he doesn't have to measure it as he can hear it directly.

There are articles dating back a long time on the abolition of ground loop effects - for instance http://www.muzines.co.uk/articles/studio-earthing-techniques/4139

My brother has a home studio, and I maintain the equipment he uses. In one case he recorded a number of lead vocals using a brand-new balanced mic cable which unknown to him was defective leading to a very low level of background hiss, occasional clicks and distortions on the recordings. No amount of 'masking' by overlaying the instruments in the mix could overcome the defects in the vocals he recorded with the duff lead, which he had to redo once the duff lead was replaced.

Good luck in eliminating the problem.
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