Re: Ground loop?

[Troy]

Do you have everything plugged into a powerbar/surge protector on one wall
socket?,If not this can cause the hum.You want everything on one
powersupply.A power conditioner would help also.


Jon Myatt > wrote in message
.. .
> I have what appears to be a ground loop, and it's driving me *mad*.
>
> My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card (well,
> rack).
>
> The balanced outputs of the DSP24 then go to the power amp.
>
> When the S90 is connected I hear a constant whirring in the background,
> which gets worse if I move the mouse. Disconnecting the S90 makes it go
> away.
>
> I've tried about five different pairs of jack-jack leads - all the same.
> Other devices plugged into the DSP24 are fine. The S90 plugged into the
> power amp directly is fine.
>
> Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
M-Audio...
>
> Thanks,
>
> Jon.
>
>
> Remove the obvious from my address to mail me. Thanks.

[Troy]

It could also be caused by power cables crossing over patch cables or even
be caused by something sitting to close to a power supply or amp in a rack.


Jon Myatt > wrote in message
.. .
> I have what appears to be a ground loop, and it's driving me *mad*.
>
> My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card (well,
> rack).
>
> The balanced outputs of the DSP24 then go to the power amp.
>
> When the S90 is connected I hear a constant whirring in the background,
> which gets worse if I move the mouse. Disconnecting the S90 makes it go
> away.
>
> I've tried about five different pairs of jack-jack leads - all the same.
> Other devices plugged into the DSP24 are fine. The S90 plugged into the
> power amp directly is fine.
>
> Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
M-Audio...
>
> Thanks,
>
> Jon.
>
>
> Remove the obvious from my address to mail me. Thanks.

[area242]

"Jon Myatt" > wrote in message
.. .
> I have what appears to be a ground loop, and it's driving me *mad*.
>
> My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card (well,
> rack).
>
> The balanced outputs of the DSP24 then go to the power amp.
>
> When the S90 is connected I hear a constant whirring in the background,
> which gets worse if I move the mouse. Disconnecting the S90 makes it go
> away.
>
> I've tried about five different pairs of jack-jack leads - all the same.
> Other devices plugged into the DSP24 are fine. The S90 plugged into the
> power amp directly is fine.
>
> Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
M-Audio...
>

If none of the other suggestions work, just use a ground lift and forget
about it. They cost a dollar or so. It's just an adapter that goes from
3-prong to 2 prong...thus removing the ground. I don't reccomend doing this
to everyone for all situations...but it sounds like this would work for you
just fine.

[Boulton]

That doesn't sound like a ground loop, which is electricity related, it
sounds more like interupt problems. Will run it past my engineer
friends.


--
Boulton
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[Robert Stevens]

I have had a similar problem in the past with a different set of hardware.

Try lifting the sheild on the balanced audio connections. This worked for
me.

Rob

"Jon Myatt" > wrote in message
.. .
> I have what appears to be a ground loop, and it's driving me *mad*.
>
> My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card (well,
> rack).
>
> The balanced outputs of the DSP24 then go to the power amp.
>
> When the S90 is connected I hear a constant whirring in the background,
> which gets worse if I move the mouse. Disconnecting the S90 makes it go
> away.
>
> I've tried about five different pairs of jack-jack leads - all the same.
> Other devices plugged into the DSP24 are fine. The S90 plugged into the
> power amp directly is fine.
>
> Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
M-Audio...
>
> Thanks,
>
> Jon.
>
>
> Remove the obvious from my address to mail me. Thanks.

[area242]

"Dale Farmer" > wrote in message
...
>
>
> area242 wrote:
>
> > "Jon Myatt" > wrote in message
> > .. .
> > > I have what appears to be a ground loop, and it's driving me *mad*.
> > >
> > > My S90 keyboard is plugged into my ST Audio DSP24 C-Port sound card
(well,
> > > rack).
> > >
> > > The balanced outputs of the DSP24 then go to the power amp.
> > >
> > > When the S90 is connected I hear a constant whirring in the
background,
> > > which gets worse if I move the mouse. Disconnecting the S90 makes it
go
> > > away.
> > >
> > > I've tried about five different pairs of jack-jack leads - all the
same.
> > > Other devices plugged into the DSP24 are fine. The S90 plugged into
the
> > > power amp directly is fine.
> > >
> > > Any suggestions? I'm tempted to ditch the DSP24 and buy a Motu or
> > M-Audio...
> > >
> >
> > If none of the other suggestions work, just use a ground lift and forget
> > about it. They cost a dollar or so. It's just an adapter that goes
from
> > 3-prong to 2 prong...thus removing the ground. I don't reccomend doing
this
> > to everyone for all situations...but it sounds like this would work for
you
> > just fine.
>
> Removing the power cord safety ground connection is a dangerous
> practice that one should not do unless you are willing to risk your life
> and the life of the eight year old daughter of the big name that is
touring
> your studio for consideration of recording his next platinum album.

That's a little extreme. It's not a great thing to make a habbit of, as it
is risky mostly for your GEAR in case of a major power surge. Also, based
on the set up he described, I don't get the impression we're dealing with a
ton of gear in a major studio. So, I would say that the platinum recording
artist and his daughter are safe as well. I've done this several times over
the years...mainly just to verify that I am in fact dealing with a ground
loop issue, and to then identify the source of it.

> You are free to do it, but you do have to accept the consequences
> of tampering with safety systems. If you do have to break a ground
> connection in the system to open a ground loop, break it on a signal
> cable.
> Are all the systems plugged into the same wall outlet or power
> strip? Is the safety ground wire intact all the way to you building
> ground point? Are there other systems in close physical proximity
> that may be radiating EMI?
> Based on your description, I'll take a bit of a guess and say that
> the problem is actually inside your computer. Computers are full
> of RF trash radiating around inside of them. Open up the computer
> and carefully examine all the faraday shielding of the case. Look for
> fingers bent, contacts corroded or losing their springiness, holes in
> the case, etc. Examine the sound card carefully, Look at the
> shielding around the analog portion of the card, particularly where
> the connectors are soldered to the board. Cracked or cold solder
> joints are a possibility, or a damaged card from a too vigorous
> insertion or removal of a cord connector. What has recently been
> changed on the computer? New fan, power supply, monitor,
> software? Look at all the cords and check for damage. Unplug and
> replug all the connectors to clean off corrosion buildup.
>
> --Dale
>
>

[Bill Thompson]

area242 wrote:
> That's a little extreme. It's not a great thing to make a habbit of, as it
> is risky mostly for your GEAR in case of a major power surge. Also, based
> on the set up he described, I don't get the impression we're dealing with a
> ton of gear in a major studio. So, I would say that the platinum recording
> artist and his daughter are safe as well. I've done this several times over
> the years...mainly just to verify that I am in fact dealing with a ground
> loop issue, and to then identify the source of it.

There's the catch...

If you really do understand power and grounding you are probably not
going to ask the question. If you are asking the question you may not
understand power and grounding, and you might assume that lifting the
safety ground solved your problem, and leave it lifted.

I too have been known, every once in a while, to use a cheater to prove
a loop exists. It is quick and easy (aka lazy)! But I am careful never
to do it if someone watching might assume it is the solution instead of
a troubleshooting tool.

I think it is a very good practice to dissuade folks from breaking a
safety ground to solve a ground loop. It is a much better practice to
advice them on the safe way to fix the problem.

I'm not arguing with your logic here... just your conclusion<G>!

Bill

[area242]

"Bill Thompson" > wrote in message
...
> area242 wrote:
> > That's a little extreme. It's not a great thing to make a habbit of, as
it
> > is risky mostly for your GEAR in case of a major power surge. Also,
based
> > on the set up he described, I don't get the impression we're dealing
with a
> > ton of gear in a major studio. So, I would say that the platinum
recording
> > artist and his daughter are safe as well. I've done this several times
over
> > the years...mainly just to verify that I am in fact dealing with a
ground
> > loop issue, and to then identify the source of it.
>
> There's the catch...
>
> If you really do understand power and grounding you are probably not
> going to ask the question. If you are asking the question you may not
> understand power and grounding, and you might assume that lifting the
> safety ground solved your problem, and leave it lifted.


I agree...he should keep in mind that his ground loop problem isn't "solved"
as much is as it is just identfied. I didn't mean to suggest that he really
consider it solved and forget about it. I just meant that he would then
know, without a doubt, that he was dealing with a ground loop and where it
is.


> I too have been known, every once in a while, to use a cheater to prove
> a loop exists. It is quick and easy (aka lazy)! But I am careful never
> to do it if someone watching might assume it is the solution instead of
> a troubleshooting tool.

Yep, same here.



> I think it is a very good practice to dissuade folks from breaking a
> safety ground to solve a ground loop. It is a much better practice to
> advice them on the safe way to fix the problem.

Yes, I agree that they should be dissuaded from using it to "solve" a ground
loop. But, I see no harm in people knowing a quick way to identify and
confirm that they are dealing with a ground problem.

I'm not arguing with your logic here... just your conclusion<G>!

Yeah, I understand what you mean...my original post sounded as though it was
a problem solved kind of thing...I think it's miscommunication, as I meant
"problem solved" in the sense that he would know for sure he had a ground
loop problem and where it was. I forget that not everyone knows about the
purpose of grounding...and the potential problems with breaking the ground
permanently.

That said, I still suggest he use one to confirm that he is really dealing
with a ground loop, and to identify it's source.