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Thread: Electrical system for studio, tips, tricks, advice?

  1. #21
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    Quote Originally Posted by ecc83 View Post
    "To this end, we standardised on IEC sockets/plugs for everything technical so the cleaning lady couldn't plug in her vacuum cleaner etc."
    Heh! In my last but one job I had a big, 2 fan industrial vac and peeps would borrow it (never fekkin' emptied it!) That I did no mind SO much but the lab boy's cable tie tails block vac pipes up disastrously! So I chopped the V long mains lead 500mm from the vac and made up an IEC male to female for it. The 13A to f'male I could lock away!

    I bet that system would not be allowed now Bobs? Non fused mains leads?! I guess the IEC skts were in fused banks?

    Dave.
    .,
    A mixture. Each edit suite or control room had a local breaker box with appropriately rated breakers--and power supplies for racks and desks were via fuses distribution units (usually at the top or bottom of each rack) with each fuse supplying a single IEC socket.
    That's what I do. I drink and I know things.
    -Tyrion Lannister (and Bobbsy)

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    All faults will select the shortest path to ground. Equi-potential grounding is the way to reduce noise in the lines. And yes, noise comes from a number of sources.

    All equipment in the studio can be on separate circuits but ALL circuits should be on the same phase of the main service.

    In an AC system, the sharing of the neutral (or return leg) between phases especially in a situation involving sensitive audio and computer equipment WILL have a potential to add noise to the lines.

    I'm not in Europe or in any area that uses a 50hz system though I have built such circuits to accommodate specialty equipment throughout my 35 years as an electrician.
    Chord with this, Teddy......

  3. #23
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    Quote Originally Posted by witzendoz View Post
    It works for all studio installs, I think you are getting this the wrong way, it you have a power point with say 12 meters of earth wire and anouther with 20 meters you get a different earth potential which can cause a loop between items plugged into the 2 power points and then connected via audio cables. RF shielding is a whole different ball game.

    There are no regulation problems as long as everything is earthed correctly. Yes all the earthing has to go back to the main swithboard MEN link with then has to be earthed to ground. If the earth is using building water pipes it has to be tested as it is not always safe to assume that the pipes are a good earth, my old studio had that problem so where the earth bond was on the pipe I ran a fat earth with to a ground stake, which made a good safe earth and reduced studio noise. But all earths have to end up wired to the same point.

    Alan.
    I was not talking about RF shielding either Alan. My point was, if you have a 'bundle' of earth wire it must have a greater inductance than a straight run and any RF or digital hash will 'sit' on it.

    I may have your idea completely wrong in my head. Can you post a rough drawing of 3 or so outlets and the earth runs back to the CU?

    I am struggling to understand you see because this is the first time I have ever heard anyone suggest INCREASING earth path resistance?

    Ah! A penny might have dropped? You are in OZ, maybe you don't use our ring main system? In a ring, every earth pin has two paths back to the CU.

    Lekkies are VERY fussy about earth impedance and you certainly could not get away with inserting extra, ad hoc bits of earth wire!

    There are radial supplies (one cable) but these are just for things like cookers and showers, nothing to do with audio.

    Dave.

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    Quote Originally Posted by cavedog101 View Post
    Equi-potential grounding is the way to reduce noise in the lines.
    I added a balanced power unit to my studio power distro rig...not that I had any significant power issues to begin with, but it's something I was thinking about for quite awhile, considering that I have a lot of analog rack gear.

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    Quote Originally Posted by miroslav View Post
    I added a balanced power unit to my studio power distro rig...not that I had any significant power issues to begin with, but it's something I was thinking about for quite awhile, considering that I have a lot of analog rack gear.
    Not so bad at 115V but balanced power systems have a serious danger potential in EU for service personnel. Used I understand in medical work but then they have their own 'aware' technicians.

    Alan, as with most of the rest of the world you do not use a ring main system so the two supplies are not really comparable.

    Dave.

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    Quote Originally Posted by ecc83 View Post
    I was not talking about RF shielding either Alan. My point was, if you have a 'bundle' of earth wire it must have a greater inductance than a straight run and any RF or digital hash will 'sit' on it.

    I may have your idea completely wrong in my head. Can you post a rough drawing of 3 or so outlets and the earth runs back to the CU?

    I am struggling to understand you see because this is the first time I have ever heard anyone suggest INCREASING earth path resistance?

    Ah! A penny might have dropped? You are in OZ, maybe you don't use our ring main system? In a ring, every earth pin has two paths back to the CU.

    Lekkies are VERY fussy about earth impedance and you certainly could not get away with inserting extra, ad hoc bits of earth wire!

    There are radial supplies (one cable) but these are just for things like cookers and showers, nothing to do with audio.

    Dave.
    All major studios use equal earth systems to reduce earth loops. I don't believe that a couple of meters of extra earth wire is a bundle, the longest earth length is the distance to the farthest power point in the system so according to your theory that earth is too dangerous to use?

    I was not talking about increasing the earth path resistance I was talking about making equal earth path resistance, how much increase will you get? Why don't you try to measure it with a meter. Also I am not talking about adding extra ad hoc bits of wire I am talking about running a nice big fat earth wire from the distribution point to each power point and being the same length.

    Read this about star earthing of mains power. The only difference in the diagram is that I was making the earth point the distribution point and the diagram shows it as a common earth point, same thing schematically.

    EDIT:

    I know it does not show equal wiring length but it is a schematic. Actually here is one more like what I am talking about.

    Actually a ring main earth will cause all kinds of earthing problems in a studio, I don't know but if you read the UK wiring rules there should be a design for star earthing that complies, I can't see why not.

    Alan

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    I am beginning to see the light Alan! No, a long earth path would not necessarily compromise safety but all installations have to be tested and SHOULD the earth impedance fall outside the requited minimum there could be a problem?

    We are also talking now about 'dedicated industrial' wiring systems where the right people can be used to do and test the work. The OP will have to get a sparks in to do the work and most domestic electricians will only install to domestic standards. Our homes are wired in twin 2.5mm with integral earth so there would INDEED have to be ad hoc 'bits of earth wire' to equalize earth runs!

    Been reading Bill Whitlock's .pdf about ground noise. Very illuminating and possibly controversial ? He is for instance not a big fan of balanced power systems since he states most of the available transformers do not have secondary windings with balanced capacitances to core/ground. (it is in fact VERY hard to find a centre tapped 230V sec' transformer in UK!) . He is also VERY suspicious of cheap, so called 'surge suppressors' and mains filters.

    Dave.

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    Yes, all electrical work should be done by a licensed electrical installer (notice I did not just say electrician LOL). If you want to get really serious run the big fat earth wire all the way to the building earthing point. Specify exactly what you want so the installer knows you want and does not just say to himself that if does not matter and does it the usual home wiring way.

    How my studio is wired is that I use 1 x 16 amp circuit (remembering we use 240 volt and at 110 volts for our US people it will be roughly 35 amps), the 16 amp circuit feeds a large good quality UPS (about 10 amps), this is then split using equal length wiring to 2 x 4 gang outlets, which in turn have the usual plug boards etc. with the mixer and recorders being directly plugged into the ganged outlets. The difference in the length of the earth through the power boards and direct is minimal and the individual boards have about the same length earth. I am in future going to build a bigger primary outlet system and get rid of the power boards. The control room only pulls about 7 amps (measured). I should point out the monitor amps are not running through the UPS as they pull a fair few amps and are too heavy a load for the UPS, however this are on the same 16 amp circuit as the UPS, I did get a small earth hum from the amps but I fixed this by lifting the audio earth on the balanced audio connections. My computers are own their own UPS and have their own outlets, but the wiring is the same length, I also use audio isolation transformers between my console, other audio gear and the computers, and this has removed all hum and buzzes.

    There are some power points in my recording area that are not part of the UPS balanced earth system, but as this usually has guitar amps etc that does not cause a problem, if there is a bass amp with a DI and there is a hum problem I just use the audio earth lift on the DI. I do however have some power points in the recording area that are on the UPS if needed.

    The air con and power to other parts of the building are on a different phases of the 3 phase into the building than the phase running the studio, the studio has it's own phase.

    Hope this is a little enlightening, no pun intended.

    Cheers
    Alan.

  9. #29
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    Thanks Alan.
    I can quite see the logic and of course when you can 'DIY' and are qualified that makes things easier. A UK 'electrician' would cost eeenough! I dread to think what a studio savvy electrican tech would charge!

    Reading Bill W's article has reminded why I was worried about your earthing regime? The note deal with the consequences of earth paths between two(say) pieces of equipment and the fact that there will always be a resultant voltage developed across the mains safety wire. This cannot be avoided but can be minimized by having the lowest possible resistances in both the earth path and the audio cable shield.

    He also make the very rarely mentioned point that most 'iso-transformer' on the market are in fact 'output' transformer. These have the advantage that they can be used anywhere in an audio feed but are grossly inferior to 'INPUT' traff which have an inter winding shield. The disadvantage of the latter of course being that they have to be within less than a mtr of the inputs.

    Input transformers are also more expensive but then Jensen's directors gotta eat as well!

    Dave.

  10. #30
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    I've got to say that we never worried about equal LENGTHS of earthing--but we were OCD careful about all earths going to a single point. Buried deep in our mains distro area was a long copper bar and every earth from a remote point was clamped to this, with a single cable to the actual earth.

    Where the earth run was a long one, we did specify a much heavier grade of cable to keep the ohms happy. We were a TV facility with multiple studios and edit suites--some cable runs were up to 80 metres. The system was designed and installed by professionals (i.e. not me).
    That's what I do. I drink and I know things.
    -Tyrion Lannister (and Bobbsy)

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