3 Jun
2015
3 Jun
'15
6:59 a.m.
Chris Caudle wrote:
On Mon, June 1, 2015 10:12 pm, Glen MacArthur wrote:
Chris,
Wow, that paper is exactly the kind of thing I was looking for.. Thanks
very much for the link and your insight..
Glen
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
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