isolating rack mounted gear from racks

Archived from groups: rec.audio.pro (More info?)

In article <1117864776.250886.19640@g47g2000cwa.googlegroups.com>,
"antonlamont45" <antonlamont45@yahoo.com> wrote:

> For days i have been trying to track down a buzz in my studio. after
> much work i finally found the source--my sampler was creating a ground
> loop by contacting the rack it was mounted on. i realized this when i
> removed the sampler from the rack and tested it out--no buzz.
>
> i plan to isolate my sampler and other gear from the rack with rubber;
> my question--is there a product that is made for this? even with
> rubber washers the screw may touch the gear, it may take more than
> that..
>

wooden racks do wonders for isolation.
--
Digital Services Recording Studios
http://www.digisrvs.com

Archived from groups: rec.audio.pro (More info?)

On 3 Jun 2005 22:59:36 -0700, "antonlamont45"
<antonlamont45@yahoo.com> wrote:

>For days i have been trying to track down a buzz in my studio. after
>much work i finally found the source--my sampler was creating a ground
>loop by contacting the rack it was mounted on. i realized this when i
>removed the sampler from the rack and tested it out--no buzz.
>
>i plan to isolate my sampler and other gear from the rack with rubber;
>my question--is there a product that is made for this? even with
>rubber washers the screw may touch the gear, it may take more than
>that..

Are you sure it was electrical contact with the rack causing the
problem? Not proximity to another unit in the rack?

When you tested it, power and signal connections were exactly as when
rack-mounted? And when you ran a temporary cable from its case to the
rack, the buzz came back?

Generally, rack-mount equipment behaves perfectly OK when mounted in a
metal rack. Because ONE item has a problem, why bother to re-mount
ALL your gear?

Out of interest, what model sampler are we talking about? A thread
elsewhere is discussing the rather unusual grounding arrangements of
an old Akai D1000.

Archived from groups: rec.audio.pro (More info?)

antonlamont45 wrote:

> i plan to isolate my sampler and other gear from the rack with rubber;
> my question--is there a product that is made for this? even with
> rubber washers the screw may touch the gear, it may take more than
> that..

I used some "shoulder" washers... The inner hole is for #10 machine
screws. Just use one behind and one in front on each mounting hole.
Cheap and relatively easy, and it completely eliminates unwanted ground
connections between gear.

Archived from groups: rec.audio.pro (More info?)

On 2005-06-04, Laurence Payne <lp@laurenceNOSPAMpayne.freeserve.co.uk> wrote:
> On 3 Jun 2005 22:59:36 -0700, "antonlamont45"
><antonlamont45@yahoo.com> wrote:
>
>>For days i have been trying to track down a buzz in my studio. after
>>much work i finally found the source--my sampler was creating a ground
>>loop by contacting the rack it was mounted on. i realized this when i
>>removed the sampler from the rack and tested it out--no buzz.
>>
>>i plan to isolate my sampler and other gear from the rack with rubber;
>>my question--is there a product that is made for this? even with
>>rubber washers the screw may touch the gear, it may take more than
>>that..
>
> Are you sure it was electrical contact with the rack causing the
> problem? Not proximity to another unit in the rack?

Those things do happen. I've had the exact same problem with a
consumer EQ with no earth connection that I had rack-mounted.
Can't recall how I solved it, but I did, and without insulating
the EQ.

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
(Counterfeit: myracuhoz@compassionate.com gatefoh@dimple.com)
What worries me is not the violence of the few, but the
indifference of the many. -- M. L. King

Archived from groups: rec.audio.pro (More info?)

On 4 Jun 2005 08:55:36 -0700, "antonlamont45"
<antonlamont45@yahoo.com> wrote:

>i just read the thread you mentioned ("Electric shocks (was: 100V
>appliance on 110v power supply" ) very interesting as this is about the
>s1000, the next sampler in the akai line after the s950. i have never
>experienced electrical shock but i can feel a very very mild unpainful
>current when touching parts of the unit where the paint has rubbed off.
> i actually have two of these samplers and experience the same thing
>with both of them, so i am tending to rule this out as a defect but as
>a characteristic of this machine.

I'd be rather worried about a "characteristic" that put enough voltage
for you to feel on the case.

Archived from groups: rec.audio.pro (More info?)

Figuring out what to do to isolate a piece of equipment means understanding
what the ground loop encompasses. From what you say you have no ground on
the equipment plug but the chassis is obviously using the rack rails to
ground itself via another piece of equipment, and that means isolating it
from the rack it is using. But that doesn't solve the bigger problem of no
ground on the equipment. There are neoprene rack screw grommets that can be
used to isolate the offending equipment from the rack, but you still need to
bleed off the chassis to a true "ground" that runs to ground. A chassis
screw can be used for a ground wire connection to some type of ground "bus"
that ties into your grounding rod outside your house.

I'd look at setting up a ground "bus" separate from your electrical box, but
tie it into the same place that your electrical box is being grounded.
Sometimes it's the cold water pipe because it goes out into the yard 3 feet
down into the ground. Sometimes it's to a specific grounding rod located
somewhere just outside of where your service panel is. Regardless, you
don't want to set up two grounds, so use wherever your household ground is
and you'll be in the proper grounding plane. But simple isolation of your
offending piece of equipment simply means YOU become the ground in certain
circumstances, and that's dangerous.

A number of good consoles will use a "star" grounding topology. It can be
easily googled and you'll see how to tie everything into a single ground,
but just because a console has the ability doesn't mean that you can't apply
the same principle to your situation. Study it, research what you have, and
come up with a total solution that is safe.

--


Roger W. Norman
SirMusic Studio
http://blogs.salon.com/0004478/
"antonlamont45" <antonlamont45@yahoo.com> wrote in message
news:1117864776.250886.19640@g47g2000cwa.googlegroups.com...
> For days i have been trying to track down a buzz in my studio. after
> much work i finally found the source--my sampler was creating a ground
> loop by contacting the rack it was mounted on. i realized this when i
> removed the sampler from the rack and tested it out--no buzz.
>
> i plan to isolate my sampler and other gear from the rack with rubber;
> my question--is there a product that is made for this? even with
> rubber washers the screw may touch the gear, it may take more than
> that..
>

Archived from groups: rec.audio.pro (More info?)

what kind of sampler is it?

You should try and lift the ground on the signal path rather than the
electrical.