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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.
  • 0
    3000 watts (peak more like 2kW average) of 240 v isolation at a price point  that may be worthwhile for a test.  Of course it is sod all use against magnetic induction, but will break any CPC gradient problems.   Try and get all the audio gear on one radial.

    Neither side of the secondary is earthed, and the lid unsrews so you can  decide if you want to carry the primary CPC on  to the secondary or use your own earthing method for the output side.


    If it works,  versions for deeper pockets /longer arms  are then available


    Inrush when turning on large transformers can be a thing. A series resistor in the phase (s) comin in and shorted out after 50msec or so once the core has at least partly magnetised can help keep the breakers in
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    Chris Pearson:
    IronFreely:

    Thanks, this is the kind of advice that makes this forum a real gold mine, you just have to sift through the occasional troll suggesting the only issue is tinnitus! 


    That's not very polite!


    I return to the question about the amplitude of this noise. Has it been measured; and if so, is it at a level which is capable of being perceived? If either answer is "no" then any attempt to abolish the noise may be a waste of time and money.


    ETA: we are talking about a "domestic home" are we not?




    We are talking about a home studio, not what you might term an audiophile's "snake oil".


    Analogue interconnections that are used in some recording setups can be a minefield for very audible "hum", and it's sensible to have at least a structured approach to the mains. The same issues can plague live performance venues too.


    It is this particular "hum" which got me thinking about how I've resolved it in the past ... and then the "balanced output" consideration to help reduce the impact of the actual mains wiring by changing it from "common mode" to "differential mode".


    If there are any electric guitars in there, you do need to take care - especially with single-coil pickups - as any electric guitarist will tell you. Electric guitars need to be earthed to prevent "cracks" and "pops" that can happen when you touch (or let go of) the strings, but this makes them effectively "common mode" - so "common mode" single-phase mains hum can be difficult to eliminate.

     


  • 0
    It seems as though every electric guitarist with a valve amp (which absolutely must be used as their monitor) will have a sixth sense for finding a power source on stage thats shared with something motorised. You do your best to give noise just the one circuit (heck if neutrals didn’t get a bit melty we’d give em their own phase) but guitarists want to plug their hairdryer in using six extensions from the cleanest power you’ve got on stage, or they’ve brought a fan and a smoke machine that they’ve got lined up on a four gang with their amp and a power drill so they can at least look good while their buzzing valves destroy my perfect mix.


    might have got a bit carried away with there.


    p.s. all really awesome guitarists tour with a power drill, fact.
  • 0
    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.
  • 0
    Well if musicns could learn to sing/play at an audible level then such hums, hisses, clicks and such would be redundant along with all the amplifiers
  • 0
    ebee:

    Well if musicns could learn to sing/play at an audible level then such hums, hisses, clicks and such would be redundant along with all the amplifiers


    Either the dog is snoring at about 18 000Hz or it turns out rock music and gunshots are indeed bad for you!


  • 0
    Not just power drills on stage in some music and dance acts example
  • 0
    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.


  • 0
    Chris Pearson:


    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.





    It won’t go away will it, surely if the problem is leakage current flowing along the signal cable screens disconnecting the appliance earth will just increase the current flowing along the signal cable screen?


  • Former Community Member
    0 Former Community Member
    It won’t go away will it, surely if the problem is leakage current flowing along the signal cable screens disconnecting the appliance earth will just increase the current flowing along the signal cable screen?


    Back to my observation earlier in this topic that asked:

    I do wonder why, if the earth leakage from audio equipment is producing its own problem of "pleasurable noise" (sic), a better design of amplifiers is appropriate? Is it a case of the equipment design being the author of its own misfortune and reliant on an earth path to dump its byproducts?


    And doesn't appear to have been challenged that the design poops on itself and all over those with sensitive hearing...............


    Regards


    BOD

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