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Old 3rd February 2004, 05:47 AM   #1
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Default transformers with electrostatic shields

Has anyone bought or compared transformers with an electrostatic shield?
I believe the claimed benefit is less RF noise.

But have people have actually obtained or been able to quantify these benefits in better perceived sound?
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Old 3rd February 2004, 07:09 AM   #2
Coolin is offline Coolin  Netherlands
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Default Double chamber transformers work very well

I have heard that the el shielding helps but not to the extent you would think. A have not heard myself so i cant compare.

Coolin
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Old 3rd February 2004, 07:18 AM   #3
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How much RF slips through a normal transformer really? Just wondering. Isn't it more lower frequencies?
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Old 3rd February 2004, 09:32 AM   #4
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As frequency increases I expect that capacitive coupling begins to occur and that's when an ESS becomes effective.
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Old 3rd February 2004, 11:14 AM   #5
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Well, I've had an ongoing problem with noise in my amp for ages. One of the things I did to try and reduce it was to make a lead case to put over the torroid. I made it out of lead sheet I got from the hardware store.

The result? Well the noise reduced quite substantially (probably about half the level.... haven't actually done measurements) but didn't go away completely. I'm not sure if this is due to poor construction of the lead sheild or whether some of the noise is simply being "induced" into the leads of the transformer.

This is actually the second transformer too. It was better than the first one, but I think maybe I got another dud, after all toroidals are supposed to have very low radiation of noise aren't they?

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Old 3rd February 2004, 01:06 PM   #6
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Default copper tape

3M makes copper adhesive tape which you can use for an exterior shield --

it's great stuff to have around anyway -- as I only "do" single sided boards I use the copper tape for ground planes, sometimes for traces.

jack
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Old 3rd February 2004, 01:37 PM   #7
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Quote:
Has anyone bought or compared transformers with an electrostatic shield?
Are U talking about a shield between primary and secondary ?

Regards

Charles
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Old 3rd February 2004, 01:59 PM   #8
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According to Lynn Olson the figure is a reduction of 40db of capacative coupling of noise..(Don't know what noise and at what frequency...) This obviously is also dependant on type of transformer...i suppose a toroidal needs a screen more than other types since capacitive coupling is high (i believe) in that type.

Electrostatic screens are almost standard in medical and measuring equipment.

How much this technical advantage translates into good sound is ofcourse debatable...but since the places I buy transformers have them standard...I'm not complaining...and only use transformers WITH screens. I just consider it good engineering practice. I.e. garbage that is not in your psu in the first place won't have to filtered out. But to answer your question ...I have never in the same circuit compared transformers with or without screen.

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Bas
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Old 3rd February 2004, 02:16 PM   #9
Gunders is offline Gunders  Norway
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Doesn't electrostatic shield mean a shieald to protect against electrostatic charges/fields?

What kind of fields do we get from a standard powertransformer?
Isn't it mainly magnetic fields.

I found this at:
http://ourworld.compuserve.com/homep...t/elect102.htm

"Some transformers have an electrostatic screen between primary and secondary. This is to prevent some types of interference being fed from the equipment down into the mains supply, or in the other direction"

Electrostatic shields is also used in audiotransformers to reduce the capactive coupling.
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Old 3rd February 2004, 02:31 PM   #10
usekgb is offline usekgb  United States
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Default Re: copper tape

Quote:
Originally posted by jackinnj
3M makes copper adhesive tape which you can use for an exterior shield --

it's great stuff to have around anyway -- as I only "do" single sided boards I use the copper tape for ground planes, sometimes for traces.

jack

Where do you get this tape? I've been looking for exactly that, and haven't been able to find any.

Thanks,
Zach
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