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Topic: OT: Studio wiring

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  1. #1
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    OT: Studio wiring

    Sorry for the OT but I know someone here has the answers for me. I am remodeling my home studio. When finished, I'll have three isolation booths for vocals and amp cabinets and two small live rooms. I want to hardwire the whole studio now before drywall so there arent any cords going in and out of the booths and live rooms. Every room and booth will have the appropriate wall jacks for XLR, 1/4", and headphones. So now I just need to know what wire to use??? I'm an HVAC contactor so I'm no stranger to wiring but I dont know specifically what I need here. My buddy that works at the local electrical wholesale house said he has some signal wire that is 18 gauge with 3 conductors and shielding. Is that what I need? He said churches use it all the time for hardwiring PA systems and stuff. I'm just at this stage right now and I need to know so I can keep moving forward. But I want to make sure that I get it right. I can just see running 1000' of this stuff and then enclosing it in drywall just to have a big universal "HUMMMM" going through my whole studio. I've got all of the power wiring under control with a brand new 200 amp service and a grounding rod outside. I just need to know what I need for all my signal paths. If possible, it would be nice if the same stuff would work for the headphone lines. Thanks for listening to the long-winded post.

    Eric

  2. #2
    Senior Member Steve_Karl's Avatar
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    Re: OT: Studio wiring

    I'd use Canare' Star Quad. http://www.tecnec.com/SearchProduct....ff=6&sort=prod

    But ... I'm not an expert.

    Also, I'd do some research on "star grounding" http://www.google.com/search?hl=en&q...r+grounding%22
    ( nothing to do with the name of the cable ) which involves where the grounds are connected on the cables and where they are lifted.

    As an example ( that may or may not work for your application ) one type of wiring system involves having all of the grounds connected at the console and lifted at the far ends.

  3. #3
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    Re: OT: Studio wiring

    Thanks Steve. This is probably more simple than what I'm thinking but I of course, have to get it right the first time. It's my understanding that the grounds for all XLR's, when wired properly, will then be grounded to the house ground when connected to the mixer. Does this sound right to everyone?

    Thanks,

    Eric

  4. #4

    Re: OT: Studio wiring

    I would recommend contacting someone like Sweetwater:
    http://www.sweetwater.com/store/detail/StarQuad/

    You could tell them your situation (wiring home studio, do-it-yourself, HVAC contracting experience) and then see if they can provide advice (for free or some $ amount) or can they recommend someone.

    They may offer some assistance for studio wiring similar to studio acoustic treatment:
    http://www.sweetwater.com/shop/studi...m_analysis.php

    You probably just need to buy a few hours of studio design expertise. Someone should be able to sell you that.

  5. #5

    Re: OT: Studio wiring

    and now for a dissenting view...

    You are covering a LOT of turf, and it has a lot more to do with design decisions than specific materials or parts!

    I can't tell for sure, so I'll offer two suggestions:
    1) You can learn this stuff, it is all rooted in basic physics, and it isn't all that complicated. But beware - the web is filled with some tremendously bad information on the subjects of system interconnection, power, and grounding!

    2) You can hire a studio designer to do this stuff for you. The good news is that almost any good designer can do this sort of thing remotely, there isn't a lot of grey area here, unlike an acoustical design<G>!

    In a nutshell:
    a) you want to insure that nothing unwanted gets into the signal path. Unwanted stuff can get in through a couple of basic mechanisms, depending on whether they are E or M.
    b) You also want to insure that ground is very nearly ground throughout the facility. This isn't difficult to understand, but it can be darned tricky to accomplish.

    The first requirement is met through careful selection and routing of all your cabling and wiring - power, analog audio, digital audio, control, MIDI, whatever! It is helped tremendously by choosing cables with proper twist rates and good shielding.

    The second requirement just requires diligence, making sure that there is only one path to ground where-ever practical, and that all paths to ground are as low an impedance as possible. There are several schools of thought on the best approach... I've had the best results using a combination of "star" grounding and "grid" or "mesh" grounding. Where you apply which is partly an exercise in trial and error.

    Beyond that I get the impression that you already know to use the best materials you can afford. High quality wire and connectors (and boxes and plates and whatever) will last longer, and work better!

    If this is an area that intrigues you, or you think you might like to be a studio designer, or you can't quite fit consulting time into the budget, or you just don't trust people then you should probably try to suss it out yourself.

    If you want to focus on other issues then you might want to hire someone to do the heavy lifting. You might be able to find someone else building a studio and trade your expertise in HVAC for their expertise in these topics!

    Whatever you do, be VERY CAREFUL if you talk to a company that also sells the stuff they include in the design!!!! This is a case where an independent consultant really can be worth their weight in gold.

    To answer your specific wire question... most installers tend to use #22AWG for permanent installations because it tends to be easier to work with, it takes up less space, and it's cheaper. There are also quite a few high quality cables in that size.

    I use #18AWG or #22 AWG... I use the thicker wire probably more for superstitious reasons than anything else<G>, both works! My favorite is a Gotham Audio cable that uses a Reussen shield. You'll also want to look at jacket construction (neoprene vs various PVC compounds), and cable make-up. A single twisted pair is probably the most common studio wire, but "Star-Quad" cables are very popular because (properly installed) they can provide better noise immunity.

    Twist ratio is a very important specification, followed closely by capacitance.

    Hopefully this will get you started!
    Bill Thompson
    Audio Enterprise
    KB3KJF

  6. #6

    Re: OT: Studio wiring

    I'm afraid I have to take exception with a couple of your points...
    Quote Originally Posted by Stephen McMahan
    If they do connect to earth or common ground - then it must be through the mixer -
    Using the mixer as the reference point is one approach, but from my experience it is one of the most difficult designs to get working, and it is even tougher to maintain.

    otherwise you're setting youself up for ground loops.
    Ground loops happen when there are two paths, of different impedances, to ground! That's all that is necessary to create a ground loop.

    As far as whether the XLR sheilds connect to ground or not, even through the mixer, is not always necessarily the case. Essentially as ling as ALL of the XLR sheild connect together and the balanced line reference requirements are mert - what you have is a system of Faraday cages which electromagnetically isolate the inside conductors from the outside world.
    That's mostly true. However, if you look at the various standards you'll see that the generally accepted approach to grounding shields is to connect the shield to pin 1, not the connector shell, and then connect pin 1 to the outside of the enclosure. If you google for "Pin 1 Problem" or Neil Muncy you'll learn more than you ever wanted to know about it<G>! Another excellent document is AES standard AES48-2005. You can download a courtesy copy at their web site.
    Many mixers do not connect the signal grounds to earth ground - this is done to avoid ground currents when using external power supplies. In this case - they create their own virtual ground.
    Stephen
    Virtual ground is a concept that is used in the design of operational amplifier circuits. It doesn't really apply here.

    At some point every piece of equipment powered from the mains must have it's enclosure connected to safety ground. How the signal ground is connected to safety ground is a matter of design, but it is always connected.

    This is not the same as the ground reference for a signal pair. Any balanced signal can be received with or without a ground reference. Any single ended signal must be referenced to ground.

    The trick to a clean audio installation it to minimize the number of paths to ground, and to keep contaminants out of the ground.
    Bill Thompson
    Audio Enterprise
    KB3KJF

  7. #7

    Re: OT: Studio wiring

    Quote Originally Posted by wst3ae
    The trick to a clean audio installation it to minimize the number of paths to ground, and to keep contaminants out of the ground.
    I agree 100%! In my studio I have only one path to the ground... .
    "Music is the shorthand of emotion." Leo Tolstoy

    Listen to me, tuning my triangle http://www.box.net/shared/ae822u6r3i

  8. #8
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    Re: OT: Studio wiring

    Thanks for all the advice guys. I came up with some CCI (Coleman) 18 gauge, 2 conductor with shielding. I ran it by a buddy who is a veteran soundman and an IBEW electrican. He said looked it up and said I should be good to go. Please explain how the twist ratio affects the signal. Thanks.

    Eric

  9. #9

    Re: OT: Studio wiring

    Quote Originally Posted by EricWatkins
    Thanks for all the advice guys. I came up with some CCI (Coleman) 18 gauge, 2 conductor with shielding.
    Well I do not know that particular brand, and I don't have time to look it up right now, but if I were wiring a studio I'd be leaning towards Gotham, Canare, Belden or West Penn and other well known players. Things to consider include:
    1) how easy is it to work with... stuffing 18AWG wire into many connectors is tough!
    2) that dreaded twist rate
    3) the shielding type
    4) how it's assembled
    I ran it by a buddy who is a veteran soundman and an IBEW electrican. He said looked it up and said I should be good to go.
    The technicians that I work with are all IBEW... however, IBEW has lots of areas of training, and not every IBEW electrician understands the finer points of wiring up a recording studio. You mention that your buddy is a veteran soundman, so you are probably ok, but just make sure. The only thing worse than wiring a studio is re-wiring it!!!!!!!!!
    Please explain how the twist ratio affects the signal. Thanks.
    This is not something that can be explained easily in a single post. There are a lot of well known audio equipment and system designers who don't get it right.

    The circuit mechanism that provides the majority of noise immunity is impedance balance. There is a common misconception that signal symmetry is responsible for noise immunity, but it isn't the case.

    The wire mechanism that provides the majority of noise immunity is the twist rate, not the shield. (Now this is not always true, it depends on how the noise is impressed on the signal conductors.)

    The short version is that a noise field is impressed on a pair of signal conductors, and if they are twisted then the noise signal is imposed on both conductors out of phase so that when the noise is applied, common mode, to an impedance balanced input the noise cancels.

    I'm re-reading that and it's way oversimplified... I'll spend some time tomorrow trying to write up a better brief explanation.

    If you really want to dig into this stuff check out book by Henry Ott and Ralph Morrison. Both are available on Amazon.
    Bill Thompson
    Audio Enterprise
    KB3KJF

  10. #10

    Re: OT: Studio wiring

    Since you still have the framing exposed, I'd find a way to put some conduits (flex or rigid) into the walls, so you *can* do wiring changes when needed. It's easier of course to wire up at the same time as well, but with conduits you'll have no "oh sh!t" moments. You can just put a snake in and pull a new cable.

    In addition to the audio stuff, I'd strongly recommend pulling some CAT5e (or CAT6) cable also, so you have the option of hooking up any network device as well, such as a laptop. CAT5e cable is dirt cheap.

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