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Plastic washers for rackmounting
Old 17th June 2005
  #1
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Plastic washers for rackmounting

Should I be using plastic washers under my rack gear between the faceplate and rack rails? I have read this helps with grounding problems while I was on the Pendulum Audio site, looking at the MDP-1 pre and they recommend you do this. Kind of a dumb question I know, but it would be from more of a preventative maintenence point of view.
Old 18th June 2005
  #2
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i've seem rubber strips somewhere that u stick to the rack(screw Plate) before u mount any piece of gear. But I think I was for vibration problems and not grounding.
Old 18th June 2005
  #3
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It's a great concept however the washer always seem to fall out on the one bastard unit that thanks to it's screws (round heads typically), is slightly overspec on the height side.....

A better method is to use a shoulder washer in front http://www.raxxess.com/product.asp?ID=493 which assures that the mounting screw is centered and not grounding the front panel to the rack rail. In back I put some glued on 1/16" thick cork strips to keep the units off the rack. In addition to the fact that this method helps control ground loops, the units will not suffer rack rash which will help conserve their resale value. Don't squish the shoulder washers with the Dewalt!!!!!!.....easier said than done when one's alone with a Yamaha D1500 or a power amp or......

The problem still remains that often the units touch each other vertically (especially those pesky screws)....Plastic sheets can help but don't block the vents....and watch out for those pesky screws to peak through....they always do.

AFAIK, balanced power makes this exercise not necessary.

When should we ship you the MDP-1???? heh

Andy
Old 18th June 2005
  #4
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If the rack requires insulating hardware, then something is likely wrong with system grounding and/or AC power. Ideally, everything in the rack would be welded together with copper braid strap!

Bri
Old 18th June 2005
  #5
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I do use plastic washers on both sides of the unit being mounted. It does seem to help isolate the units from each other. Some combinations of gear just don't do well near each other sometimes. Especially transformerless gear, depending on how well it's designed.

I'll look into the above method, maybe that's better. Thanks.
Old 18th June 2005
  #6
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Jason, in this day and age, anything is possible. However, in a more ideal setup, there should be NO voltage potentials from one chassis to another.

Transformerless??? Wowzer...as in hot-chassis AC-DC AM/FM radios which had no power transformer? I was unaware that anyone was still using/selling rattlesnakes like that....

In any case, for small to medium sized studios, keep all of the audio gear fed from the same phase leg in the breaker box.


Bri
Old 18th June 2005
  #7
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No, I just meant a transformerless signal path. I've noticed that stuff with transformers usually has less hum problems, but not always.
Old 18th June 2005
  #8
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I use shoulder washers on both sides of the faceplate. Besides keeping everything isolated better the washers prevent any cosmetic damage to the rack holes. Very important in this eBay age!

I also tape over any protruding case screws with electrician's tape. Besides the obvious cosmetic protection this provides, it also prevents metal from touching metal.
Old 18th June 2005
  #9
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Thanks guys. There is no ground issue but I move some gear around to a few spaces so it is more of a preventative thing. I am just about to move some gear into different racks so it was just to save me a headache of taking everything out again just to put washers in later. Good info. thumbsup
Old 9th November 2006
  #10
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I dont understand how they would casue a grounding issue...maybe im dumb i dont know... unless your using one as a chassis ground or using one on your ground wire which is simply moronic

The good thing about having plastic washers on your rack screws is that it doesn't scratch up your gear most rack mounted gear I deal with comes with pastic washers on the rackscrews.
Old 9th November 2006
  #11
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I use nylon washers only on the front. They're tapered. They can be found at Napa auto stores where they keep all the nuts and bolts.
Old 9th November 2006
  #12
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Quote:
Originally Posted by clarose_lapro View Post
I dont understand how they would casue a grounding issue...
There are three paths (at least) to ground in every piece of gear -

1.) The audio 'shield" which should be disconnected on one end (of a balanced line)
2.) The 3rd pin of the AC cable
3.) The chassis (on most - not all - gear

Star grounding assumes only one path to ground via a connected 12ga wire, with shields lifted, grounds lifted and chassis's isolated. The easiest way to isolate the chassis is via wood rackrails which work excellent. The second best way is not with nylon washers, it's with these:

http://www.danabgoods.com/Humfrees/
http://www.musiciansfriend.com/produ...0&src=3SOSWXXA

If you must use metal rack rails, Humfrees are the most practical (easiest) solution for grounding issues. The screw cannot touch the chassis and the chassis cannot touch the rail.
Old 9th November 2006
  #13
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[QUOTE=clarose_lapro;960438]I dont understand how they would casue a grounding issue...maybe im dumb i dont know... unless your using one as a chassis ground or using one on your ground wire which is simply moronic
[QUOTE]

No, I am not using any of the rails as a chassis ground. The whole point of this old thread was spauned by something I read on the Pendulum Audio site. They suggest using plastic washers underneath the rack ears to eliminate any possibilities of a ground issue. That's all. I have no ground issues, buzz or hum.
Old 9th November 2006
  #14
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I recently installed nylon washers and it made a difference. Additionally I put a strip of electrical tape between two problem units. A Behringer Headphone amp and Patchbay. Go figure!

Anyway between the two, hum is now gone and I can get on with it...
Old 9th November 2006
  #15
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[QUOTE=Colin Gaucher;960990][QUOTE=clarose_lapro;960438]I dont understand how they would casue a grounding issue...maybe im dumb i dont know... unless your using one as a chassis ground or using one on your ground wire which is simply moronic
Quote:

No, I am not using any of the rails as a chassis ground. The whole point of this old thread was spauned by something I read on the Pendulum Audio site. They suggest using plastic washers underneath the rack ears to eliminate any possibilities of a ground issue. That's all. I have no ground issues, buzz or hum.
Colin - nylon washers on both sides is a good start, but will only work 100% if you're using nylon screws and I hate those things. If you're using steel screws, there's still a chance of having the chassis ground of any piece of gear interact with another piece of gear. The nylon must insert thru the rack hole on the piece of gear so that there is no chance of the screw touching the metal chassis, and no chance for the chassis to touch the rack rail. Without that it's just a crapshoot, and grounding is hard enough without wondering if maybe a screw might be making contact. The humfrees are like nylon washers on either side, but they also go thru the rack ear hole, making it impossible for the screw to toouch the chassis. Highly recommended.

PS - some people actually do use the metal rack rail as a ground, but personally I wouldn't subscribe to that. It introduces too many variables into the equation IMO.
Old 9th November 2006
  #16
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Quote:
Originally Posted by drBill View Post
The nylon must insert thru the rack hole on the piece of gear so that there is no chance of the screw touching the metal chassis, and no chance for the chassis to touch the rack rail. Without that it's just a crapshoot, and grounding is hard enough without wondering if maybe a screw might be making contact.
Thanks drBill. The washers I use have a little part that eliminates any chance of the metal screw touching the rail or the racked gear itself. thumbsup
Old 9th November 2006
  #17
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Quote:
Originally Posted by Colin Gaucher View Post
Thanks drBill. The washers I use have a little part that eliminates any chance of the metal screw touching the rail or the racked gear itself. thumbsup
Cool! Care to share a link to them?
Old 9th November 2006
  #18
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I found them locally in a music shop. They are small, round black washer with a little nipple or shoulder that extends into the machined screw slot under the faceplate of the piece of gear being mounted. That coupled with the nylon washer under the screw head seems to work marvelously. They are made by Raxxess if memory serves me correctly. I bought them in a bag of 100 pieces for about $5. No mucking around like the Humfrees.

I should not, in a post above I mentioned the screw doesn't touch the rail which is false. Obviously the screw has to touch the rail to be effective. The faceplate of any racked gear I own does not come into contact with the rail and the mounting screws are isolated from the faceplate by the nylon washers on top and underneath.
Old 9th November 2006
  #19
SK1
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Quote:
Originally Posted by sysexguy View Post

AFAIK, balanced power makes this exercise not necessary.


Andy

So if I have a balanced isolation transformer like the Furman IT-1220, I wouldn't need to isolate my rack gear with washers ?

Old 30th July 2016
  #20
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Quote:
Originally Posted by drBill View Post
There are three paths (at least) to ground in every piece of gear -

1.) The audio 'shield" which should be disconnected on one end (of a balanced line)
2.) The 3rd pin of the AC cable
3.) The chassis (on most - not all - gear

Star grounding assumes only one path to ground via a connected 12ga wire, with shields lifted, grounds lifted and chassis's isolated. The easiest way to isolate the chassis is via wood rackrails which work excellent. The second best way is not with nylon washers, it's with these:

Humfree Rack Isolators
Humfrees Rack Isolation Tabs | Musician's Friend

If you must use metal rack rails, Humfrees are the most practical (easiest) solution for grounding issues. The screw cannot touch the chassis and the chassis cannot touch the rail.
Hi drBill, I'm looking for these Humfrees, but can't seem to find any. Do you know if anyone still does them. I live in the uk but if need be will buy over seas.
Old 30th July 2016
  #21
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hi louis - I'm not sure where you can find them overseas - you might try contacting the manufacturer in one of the above links, OR, you can get them at Sweetwater. They look to be in stock....

Humfrees Rack Isolation Tabs | Sweetwater.com
Old 30th July 2016
  #22
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Quote:
Originally Posted by drBill View Post
hi louis - I'm not sure where you can find them overseas - you might try contacting the manufacturer in one of the above links, OR, you can get them at Sweetwater. They look to be in stock....

Humfrees Rack Isolation Tabs | Sweetwater.com
Thanks drBill, ordering now.
Old 30th July 2016
  #23
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I have never used washers and never had any issues.
Plugging whatever is in the rack into one outlet always does the trick for me.
30 some years now I guess.
Plastic washers with metal bolts never made sense to me.
Old 30th July 2016
  #24
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drBill's Avatar
Quote:
Originally Posted by cavern View Post
I have never used washers and never had any issues.
Plugging whatever is in the rack into one outlet always does the trick for me.
30 some years now I guess.
Plastic washers with metal bolts never made sense to me.

Sometimes you get lucky. Not everyone can get to one outlet, and lets face it - 50% of the time, luck fails.... In my new install I didn't star ground and didn't take any rack oriented precautions, and everything is dead quiet. But I put in a new filtered and isolated sub panel with 4 circuits, and ran straight 10Ga wires to 4 outlets from each of the 4 circuits, and all studio gear AC comes off those 4 circuits. No issues.

Agreed on the plastic washers and metal bolts, but those hum frees are not just washers - they make a sleeve inside the rail so the screw cannot touch the piece of gear in any way.
Old 30th July 2016
  #25
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Quote:
Originally Posted by cavern View Post
I have never used washers and never had any issues.
Plugging whatever is in the rack into one outlet always does the trick for me.
30 some years now I guess.
Plastic washers with metal bolts never made sense to me.
Well thats good to here, you've had no problems. But i have in the past and while I'm building another rack, I'm just trying to omit possible problems.

The point of these Humfrees Thingy's is that it does not matter wether the bolts are metal or solid gold, as no part of them is going to touch any equipment as it goes Through the hole, or the rack strip for that matter. Quite a good invention for a simple bit of plastic. I can't believe that no one else besides sweetwater seems to be selling these.
Old 30th July 2016
  #26
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Yeah, they never seemed to catch on. I think because they're a royal PITA to put on. Especially if the gear is heavy. But they do what they are advertised to do. Good luck with the new rack!
Old 30th July 2016
  #27
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Quote:
Originally Posted by drBill View Post
Sometimes you get lucky. Not everyone can get to one outlet, and lets face it - 50% of the time, luck fails.... In my new install I didn't star ground and didn't take any rack oriented precautions, and everything is dead quiet. But I put in a new filtered and isolated sub panel with 4 circuits, and ran straight 10Ga wires to 4 outlets from each of the 4 circuits, and all studio gear AC comes off those 4 circuits. No issues.
In your case as in mine, it isn't luck though.
Old 30th July 2016
  #28
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I just used the plastic washer from my raxess screws front and back yesterday.
Old 30th July 2016
  #29
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Quote:
Originally Posted by louis1 View Post
Thanks drBill, ordering now.
Don't use these--they're terrible! Use the Shoulder washers on both sides of the screw holes and put some insulation on the sides of the rack ears so they don't touch the side of your rack.
Old 30th July 2016
  #30
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Quote:
Originally Posted by deuc647 View Post
I just used the plastic washer from my raxess screws front and back yesterday.
Are these better in some way.
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