MOTM

> ----- Original Message -----
> From: motmclergy <ldavid777@...>
> Some say have the studio on it's own phase.  Now I may be stupid, but as
far as I can tell, I only have two phases (typical residential 100 amp
service).

You are not missing much.  Your typical North American power supply is a
single-phase center-tapped 240 volt winding with the center tap grounded at
the service entrance.  That gives the appearance of 2 phases.  But, in
reality the two 120 volt legs are simply 180 degrees out of phase due to the
center tap of the transformer being the neutral.

You are pretty much wasting your time worrying about which of these hot legs
you place your studio on.  Since both share a common neutral, noise is just
as likely to enter because of neutral fluctuations as through the hot leg.
For example, let's say you ran a dedicated 4 wire 240 volt line over to your
studio.  That's hot 1, hot 2, neutral and ground.  You thought, I'll put all
the dirty stuff on one leg and the clean stuff on the other.  Wrong!  Only
the unbalance between load clean and load dirty will travel in the neutral.
The balanced component will swap from one leg to the other.  So, if you run
two circuits, run two completely separate circuits so you have a separate
neutral for clean and dirty.  That is much more importat than whether they
are on the same leg or not.  You are reducing the amount of common neutral
to only what is in your box and out to the transformer.  And, that is much
bigger wire which will be less impacted in terms of voltage fluctuations
than the # 12 wire you may run to the studio.

> Anything else I should do/not do for clean power?

There are a few things you should look out for:

 - Light dimmers and motor speed controls.  They are nasty little critters
that use AC for partial cycles.  They will introduce noise, unually in the
form of odd harmonics of 60Hz back into the line.

- Printers and copiers have especially nasty power supplys.  Keep them off
of your studio circuit.

- Multiple earth grounds.  Your house should have only one common ground
point for earth connections.  The most common violation I see of this is
where the phone company or cable company has picked the first convenient
ground (like a metal water pipe) to attach their equipment ground.  Ferret
out these beasts and get rid of them.  Ground everything to one point.  This
will help you avoid lightning damage.  In my opinion, most home related
lightning damage is not from spikes that come in on the hot line.  It is
from rise in the ground potential sorrounding the strike.  Your surge
protector won't protect you from those.  A single point ground keeps all
your stuff at the same level so that voltage rise is not an issue.  Think of
the birds on the wire.  Both feet on the wire = OK.  One foot on the wire
and one on the pole = burnt toes.

- Inadvertent neutral to earth bonds. These need to always be kept separate
as they are the single biggest cause of ground loop hum in my opinion. Get a
voltmeter and check voltages from the signal ground point of one piece of
gear to another.  It should be damn near zero.  If it is not, you will have
neutral current flow in the sheilds of your audio cables.  Here comes that
hum.  Many times, this voltage check will help you determine where your
problem is.  More often that not, you will find some piece of gear that has
signal ground somehow connected to neutral and not earth.  Stinkin' guitar
amps are the worst.

- Lack of grounds.  Here is another issues to watch out for.  Let's say you
have a bipolar supply for your synth power supply.  You find two connections
to the transformer and see no particular reason to have a 3 wire cord.
Wrong!  Connect that ground wire to the chassis of the power supply.  If you
let the chassis float, it will likely float at 50% of line to neutral
voltage.  That will cause you greif in a variety of ways.

> p.s.  I'm still building my modular; like so many, I've been fully
occupied by the necessaries of life for the last, ah, 2 years or so :)

I'm going on 6 years I think. :)  Paul S.  When did you start this crazy
MOTM thing.
Larry Hendry (motm customer # 006 and professioal high voltage person)