[LAU] Shielded electrical wiring for studio (or not)

[Glen MacArthur]

Chris Caudle wrote:
> On Mon, June 1, 2015 10:12 pm, Glen MacArthur wrote:
>>  I'm in the middle of building a new recording studio and soon will be
>> starting to rough-in the electrical wiring, the studio is not very large
>> but will have a separate uncoupled control room and a studio
>> floor/rehearsal space. I'm curious what the prevailing wisdom is on
>> using
>> shielded wire (or metal conduit tubing) for the electrical wiring..
>
>
> This is a good overview of power systems interaction with audio systems
> written by Jim Brown of Audio Systems Group:
>
> http://www.audiosystemsgroup.com/SurgeXPowerGround.pdf
>
> Look for the section titled "Preventing Magnetic Coupling" for a
> description of ways to minimize magnetic coupling of power frequency
> noise.
>
>>  I'm in Canada where we use 120V AC
>
> In North America you can also use 240V AC single phase, which has the
> advantage of using only half the current (reduces magnetic coupling) and
> has anti-phase voltages on each power leg (can help reduce leakage
> currents onto neutral and safety ground).
> In short, twisting the power legs helps, and running in metallic conduit
> helps, thicker conduit more than thinner, so rigid still has better low
> frequency shielding than EMT.  Your labor costs go up a lot if you run
> rigid conduit, even EMT is probably pretty high labor costs.
>
>> would be 'BX Cable' which is insulated wiring in a flexible corrugated
>> aluminum shell
>
> Don't bother with that unless you have to because of safety
> considerations.  I don't think you can use Romex in commercial
> installations, there needs to be some type of armor (excuse me, I guess
> that would be armour in Canada) to protect the wiring from insulation
> cuts.
>
>> and the last option would be metal conduit which is
>
> There are actually two variants of metallic conduit, rigid which is
> thicker walls, and EMT, "electrical metallic conduit" which has thinner
> walls and is therefore easier to bend and install.
>
> That paper goes into details.  Don't overlook that the shielding is
> cumulative, so if you can afford the labor costs (or labor time if you are
> installing the conduit yourself) there could be advantages to using steel
> conduit for the power and the audio cabling.  Personally I don't find that
> power line coupling into line level twisted pairs is usually a problem,
> and having your microphone lines well shielded doesn't really help when
> the problem is power line pickup in your guitar pickups.
>
>> A second related question: Is LED lighting better than CFL for noise? I
>> am
>> aware that dimmers are always a bad idea so I will be avoiding them and
>> I'd prefer to use LED unless they are worse for causing noise..
>
> I have not seen any definitive tests of conducted or radiated noise
> between LED and CFL, but they both use similar styles of power supply
> design, so to a first order approximation they are probably the same.
>
> --
> Chris Caudle
>
>
> _______________________________________________
> Linux-audio-user mailing list
> Linux-audio-user at lists.linuxaudio.org
> http://lists.linuxaudio.org/listinfo/linux-audio-user
>

Chris,

Wow, that paper is exactly the kind of thing I was looking for.. Thanks
very much for the link and your insight..

Glen