MOTM

Hi all,

I've been trying to get some info about this on the web and am striking out. I suspect
some of you know about this so I thought I'd ask here.

I'm building a home studio in my basement and have read comments here and there that
it's important to have clean power. Examples are given about not having studio power be
on the same phase as the HVAC system, etc. 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). The best I can do I think, is try to group the "least dirty" (whatever that
means exactly) ckts on one phase and use that one for the studio also. I figure I'll probly
only need one 20 amp ckt to get enough juice (maybe 2?), but I've heard it's good to have
lights on a separate ckt, which I could do (on a 15A I guess). Is this right? Anything else I
should do/not do for clean power?

Then of course is the issue of power conditioning. I have a UPS with a little brownout
protection and the usual surge stuff - nothing fancy. Do I need something better? I want
to make good records and not have my power be the weak link in the audio quality chain.

Unless everyone is interested in this stuff, offline responses are probly best. Thanks for
reading.

Larry David (motmclergy)
ldavid777<delete>@...

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 figure I'll probly
>only need one 20 amp ckt to get enough juice (maybe 2?), but I've
>heard it's good to have
>lights on a separate ckt, which I could do (on a 15A I guess). Is
>this right? Anything else I
>should do/not do for clean power?

That's essentially what I've done in my studio. All sockets for audio
gear (synths, mixer, amplifier) are on one breaker. All computer gear
is on another breaker. Lights are on another breaker, and the rest of
the house is on separate breakers as well.

> ----- 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.

Larry did a great job of describing this topic. For more in-depth reading there is a book by Philip Giddings titled "Audio Systems Design and Installation". You can also read some of his articles here:

http://www.engineeringharmonics.com/papers/papers.html

Another good source of info on this subject are the Rane technical papers, particularly under the "Wiring, Interconnection & Grounding" section:

http://www.rane.com/library.html

And, lastly but definitely not least, is the information presented by Bill Whitlock on the Jensen Transformers website:

http://www.jensentransformers.com/apps_wp.html

I've attended a few of his seminars on shielding and grounding and have always come away with some more insight into this vast topic.

One last thing. Get rid of all MOV's in your system. These can cause many different problems. The only effective surge protection made is by Surgex or Zerosurge. I particularly like the Surgex products and use them exclusively in my stage and studio setups:

http://www.surgex.com/

Ivan

Thanks for all the helpful info - this list is great! :)

So far I understand the following: assuming I have separate ckts for
the studio, it doesn't matter which "phase" they are on (which side of
the panel). So far so good.

> - Multiple earth grounds.

Now this is a little more complicated.

> Your house should have only one common ground
> point for earth connections...

Ok, I have one twisted copper ground wire from my panel to the city
side of my water line, and another similar copper wire (from the panel)
connected to a rod buried in the ground just under the service
entrance. Does this count as one common ground point?

Lawrence David wrote:

>And as for MOVs - those are the cheap surge protection devices in yer
>typical plug strip? What exactly is the problem with these? My whole
>studio is infested with them! :(
>
>

Can we hear more about why not to use computer type surge protection on
synth circuits? What's wrong with MOVs (Metal Oxide Varistor)?

And Ivan wrote:

One last thing. Get rid of all MOV's in your system. These can cause many different problems. The only effective surge protection made is by Surgex or Zerosurge. I particularly like the Surgex products and use them exclusively in my stage and studio setups:

http://www.surgex.com/

Ivan

Ok, I went to the SurgeX site and saw the dealer list. Where do you buy yours, Ivan?

-Richard Brewster

Here's a good overview regarding problems associated with MOV surge supression:

http://www.surgex.com/library/42001-2.html

I spent a couple of hours and went through all my power strips and rack power panels cutting out the MOV's. If I see them inside gear I take those out too.

Ivan