Go easy on me, I'm a beginner....

I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.
This leads to a lot of ground hum. I can solve this by defeating the
ground on one circuit (with a 3-to-2-prong adapter), but this is
obviously a BAD idea.

I got to thinking though, what if I connected the grounding lug on the
adapter to the AC ground on the first circuit? I'd use 12-gage copper
wire. Then everything's grounded but devices on circuit 2 are
referencing ground from circuit 1. So my questions:

1) Is this safe?
2) Will it solve my hum or just create a giant ground loop?
3) Is there a cheaper/better solution? I could spend a little bit on a
commercial part, but over $80 or so gets hard.

Any help is greatly appreciated. Simple yes/no answers are good, but
the more you can educate me on what is happening, the better. Thanks in
advance guys.

Recently I bought and moved into a house that had the old two wire electric
system in it. serviced by two of the old screw in fuses. Before I moved in,
and at great expense, I had a local contractor install a 100 amp breaker box
and the local utility had to change over the wiring comming in from the
pole.
I've been running most of the new circuts and changing the old ones to be
serviced by their own breakers in the panel box. Runnig the new three
conductors system where I can without ripping the walls and ceilings to
shreds.
The only thing that I can see that could cause you a problem (probably a big
one too) is if any of the wiring is reversed.
Let me explain. I have this handy gadget that looks like a pen with a beeper
and a led on it. I use this to tell me if there is current on a set of
wires. It also tells me which one of the wires is the hot side. Only once in
this project have I found a pair of wires that was reversed. But I've been
told that if I had just blindly attached them without checking I could've
caused a fire hazzard at worse and blown the main breaker at best.
Now when I hook the new circuts up ALL of the returns are joined togather on
a buss bar that also joins all of the third conductor (common ground). The
hot sides go into the breakers. (load vs returns)
So if (big word there) you are sure that both circuts are serviced by the
same breaker box and you know which sides are the hot sides and which ones
are the returns I don't think you'll have any problems. Unless of course an
electrical code inspector sees it and complains.

--
Pray for success please. :-)
http://web.nccray.net/jshodges/mommasaid/sss.htm
"FollowTheMusic" wrote in message
oups.com...
Go easy on me, I'm a beginner....

I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.
This leads to a lot of ground hum. I can solve this by defeating the
ground on one circuit (with a 3-to-2-prong adapter), but this is
obviously a BAD idea.

I got to thinking though, what if I connected the grounding lug on the
adapter to the AC ground on the first circuit? I'd use 12-gage copper
wire. Then everything's grounded but devices on circuit 2 are
referencing ground from circuit 1. So my questions:

1) Is this safe?
2) Will it solve my hum or just create a giant ground loop?
3) Is there a cheaper/better solution? I could spend a little bit on a
commercial part, but over $80 or so gets hard.

Any help is greatly appreciated. Simple yes/no answers are good, but
the more you can educate me on what is happening, the better. Thanks in
advance guys.

FollowTheMusic wrote:

Go easy on me, I'm a beginner....

I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.
This leads to a lot of ground hum. I can solve this by defeating the
ground on one circuit (with a 3-to-2-prong adapter), but this is
obviously a BAD idea.

I got to thinking though, what if I connected the grounding lug on the
adapter to the AC ground on the first circuit? I'd use 12-gage copper
wire. Then everything's grounded but devices on circuit 2 are
referencing ground from circuit 1. So my questions:

1) Is this safe?

Nope. Probably not within code either. While the scenario where
it would be unsafe is unlikely, it is not unknown. And the consequence
is a fire starting inside of your walls.


2) Will it solve my hum or just create a giant ground loop?

Yes it will solve your hum, and is marginally safer than leaving
the safety ground disconnected.


3) Is there a cheaper/better solution? I could spend a little bit on a
commercial part, but over $80 or so gets hard.


Nope. You have to setup your equipment with different ground
references, which is not rocket science, but is not simple either.
The nutshell is you plug in your gear to the different power circuits.
I'll refer to them as safety ground group A and B. Whenever
you send a signal between something in group A and something
in group B, you need to break the signal ground path without
losing your shielding.
You do this by having all the connections go via balanced ( usually
XLR ) connections or via optical connections. Optical ones don't
need to be touched, they don't have a signal ground. The balanced
connections you need to open up the cable and disconnect the
shield ground wire *at one end only* of the cable. Make sure
that the shell of the connector at that end doesn't connect to the
shield via one of the mechanical grips. The shell will pick up
ground from the thing it is plugged into. For your sanity, pick one
end of the cable to do this, and flag these modified cables with
colored tape or something so you know that they have been
deliberately broken like this.
Oh yeah, important safety check here. Measure the voltage
between the ground pins of group A and B. It should be zero
or fractions of a volt. If it has noticeable voltage, then there is
a deeper problem that is beyond the scope of this, and
may be hazardous to your health and your equipment's health.
Measure this with nothing plugged in, and with equipment
operating.


Any help is greatly appreciated. Simple yes/no answers are good, but
the more you can educate me on what is happening, the better. Thanks in
advance guys.

Take your time, label everything, and recheck your work for
mistakes. especially the one you are SURE you got right the
first time.

--Dale

FollowTheMusic wrote:

I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.

My god, man, how much equipment do you have? I ran an Ampex MM1100 (2"
analog recorder), a Soundcraft console, Hafler amplifiers, some
outboards, on one 15A circuit. What are you running that blows fuses if
you put it all on one circuit?

"FollowTheMusic" wrote ...
Go easy on me, I'm a beginner....
I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.

Does your equipment really add up to more than 15A?
Seems very unlikely for a setup "on a very small budget".
If you are tripping breakers, it may be an indication of
other problems.

This leads to a lot of ground hum. I can solve this by defeating the
ground on one circuit (with a 3-to-2-prong adapter), but this is
obviously a BAD idea.

I got to thinking though, what if I connected the grounding lug on the
adapter to the AC ground on the first circuit? I'd use 12-gage copper
wire. Then everything's grounded but devices on circuit 2 are
referencing ground from circuit 1. So my questions:

1) Is this safe?

NO. It could be done safely if you knew what you were doing,
but few people do, and you wouldn't be asking here if you did.
Do they teach anything as practical as electricity and power
distribution at your school? Can you find an EE undergrad who
can check it out for you?

Certainly spend $1~2 on a circuit tester plug. They have three
neon lights which indicate if the plug is wired properly.

2) Will it solve my hum or just create a giant ground loop?

It has the potential of solving your hum, but it has an equal
chance of creating a worst problem up to and including
burning down your apartment building. :-((

3) Is there a cheaper/better solution? I could spend a little bit on a
commercial part, but over $80 or so gets hard.

You are treading on dangrous ground with power wiring.
My first plan of attack would be to confirm that the plugs
are wired properly (with the cheap tester plug).
My second plan of attack would be to figure out why you
are blowing breakers on a 15A circuit.

Thanks for all the input so far. Let me add some more info:

1) It's not just my audio equipment that is 15amps. Like I said, my
apartment wiring is fixed. I have 2 15amp circuits that must accomodate
every electrical device I own, incl. some decently massive computers.
I'm gonna get a Seasonic Power Angel to measure each device's load and
maybe redistribute, but with only 2 circuits I can't do much.

2) I bought a Radioshack outlet tester and tested every outlet; they
all came up good.

3) People seem to think my idea is pretty dangerous -- care to explain
why? IF things are wired correctly, the grounds from both circuits are
the same because they are both tied to the grounding bus at the breaker
box, right? (I'm trying to learn here). Does it take incorrect wiring
to make this unsafe, or can it happen under normal conditions?

4) I understand the idea of cutting the shield on any signal cables
bridging the two AC circuits, but, um, cable shields are good, right?
How much of an impact could this make?

I don't know if I can get an ideal solution in my situation, but it's
frustrating that I can get a clean signal by lifting one circuit
ground. I was hoping to preserve that while maintaining a safe setup.

People seem to think my idea is pretty dangerous -- care to explain
why? IF things are wired correctly, the grounds from both circuits are
the same because they are both tied to the grounding bus at the breaker
box, right? (I'm trying to learn here). Does it take incorrect wiring
to make this unsafe, or can it happen under normal conditions?

If your apartment has 230V for an electric dryer, it's possible that each of
your 15-amp circuits is on a separate phase. I would not go around
connecting the grounds of these circuits.


I don't know if I can get an ideal solution in my situation, but it's
frustrating that I can get a clean signal by lifting one circuit
ground. I was hoping to preserve that while maintaining a safe setup.

Lifting the ground connection on one amplifier does not necessarily create
an unsafe condition.

FollowTheMusic wrote:
I have a small setup on a *very* small budget. I live in an apartment
with mediocre wiring that I cannot change. In order to avoid tripping
breakers, I have to spread my equipment across two 15-amp circuits.
This leads to a lot of ground hum. I can solve this by defeating the
ground on one circuit (with a 3-to-2-prong adapter), but this is
obviously a BAD idea.

Yes, this is illegal.

I got to thinking though, what if I connected the grounding lug on the
adapter to the AC ground on the first circuit? I'd use 12-gage copper
wire. Then everything's grounded but devices on circuit 2 are
referencing ground from circuit 1. So my questions:

1) Is this safe?

It might be, but it;'s also illegal.

2) Will it solve my hum or just create a giant ground loop?

For the most part, it will tend to make your problems worse.

3) Is there a cheaper/better solution? I could spend a little bit on a
commercial part, but over $80 or so gets hard.

Draw out your grounds and eliminate the ground loops. Figure out how
to wire things up so there is one and only one path to ground from each
piece of equipment and each other. If everything is balanced, this should
only require cutting some shields on signal cables at one end. If you
have unbalanced gear, it may require transformers.

If you don't have ground loop problems, it doesn't matter _which_ circuit
you are using because you still have a good solid ground.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

FollowTheMusic wrote:
Thanks for all the input so far. Let me add some more info:

1) It's not just my audio equipment that is 15amps. Like I said, my
apartment wiring is fixed. I have 2 15amp circuits that must accomodate
every electrical device I own, incl. some decently massive computers.
I'm gonna get a Seasonic Power Angel to measure each device's load and
maybe redistribute, but with only 2 circuits I can't do much.

There are some things that simply don't make any sense to try to work
around, and inadequate wiring for the 21st Century is one of them. We
went through this in offices back in the late '80s where about the only
thing electrical that was expected beyond lighting was a clock and an
electric typewriter. Breakers started tripping when when someone
donated a coffee pot, and all hell broke loose when a couple of people
got PCs. The only solution was to add additional circuits.

That's what you need. You might be able to get away with running some
extension cords around the apartment and distributing the loads better.
It's ugly and might raise some insurance liability issues if your
building burns down, but you can probably work it out. But if you
really can't juggle things to get your audio equipment on a common
circuit, and one that's different from the circuit powering things that
routinely switch inductive loads on and off like a refrigerator or air
conditioner, you really should have a serious talk with your landlord
about bringing the building wiring up to current standards (not the
same as "code") and start thinking of moving - because he won't want to
do that.