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Old 14th June 2007, 02:19 AM   #1
jarthel is offline jarthel  Australia
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Default electrostatic shield - nice to have or recommended or doesn't matter?

as title. thank you.
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Old 14th June 2007, 04:33 AM   #2
jnb is offline jnb  Australia
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I guess it depends on where, and what's nearby. I believe that all conductors have capacitance to other nearby conductors and shields help.

Jacco Vermeulen recommended a paper to me that covers es and em. I found it to be a good read. http://www.diyaudio.com/forums/showt...27#post1229027
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Old 14th June 2007, 11:40 AM   #3
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Do you mean those little sheets you put in the dryer with your cloths? Around here in the winter when the heater dries the air they do help reduce static cling , so I suppose I can recommend them. In the summer they don't seem to make much difference.
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Old 14th June 2007, 11:56 AM   #4
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I expect you mean a grounded thin metal shield between primary and secondaries in a power tranny. If that is what you mean, then, yes, I think it's a good idea to shield the secondaries from mains-borne noise, but not essential.
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Old 14th June 2007, 12:15 PM   #5
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I hear split bobbin transformers are nearly equivalent in performance to E/S shields. The idea is to reduce capacitance between primary and secondary windings, thereby prohibiting HF hash and noise from entering the secondary winding(s). The interwinding shield shunts this hash to ground before it reaches the secondary.

After much deliberation, I chose a shielded tranny for my B+ circuit, and plain jane split bobbin trannies for all filament and supplementary supplies.
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Old 14th June 2007, 12:17 PM   #6
jnb is offline jnb  Australia
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Using some of my new found knowledge, now that you mention it Ray Moth, could an electrostatic shield between the windings of a transformer reduce interwinding capacitance maybe?

edit- beat me to it, zigzagflux
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Old 14th June 2007, 01:26 PM   #7
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Between primary and secondary windings in a power transformer?: My vote: Nice to have
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Old 14th June 2007, 01:39 PM   #8
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Probably nice to have in some situation.

Removing and reconnecting the shield results a tiny, almost inaudible difference in my system.

Much less audible than power cables but a lot less controvercial
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Old 14th June 2007, 03:17 PM   #9
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Quote:
Originally posted by zigzagflux
The idea is to reduce capacitance between primary and secondary windings

Maybe I should clarify. With an E/S shield, I don't specifically reduce any capacitance; I actually am installing a guard between the primary and secondary. Now, instead of a large C between primary and secondary, I have a C from primary to shield, and another C from secondary to shield. Ground this shield, and common mode noise is effectively shorted to ground. It can't reach the secondary.

With the split bobbin design, I would say you are actually lowering capacitance between primary and secondary, due to physical winding layout. There's no guarding going on there.
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Old 16th June 2007, 10:47 PM   #10
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Jarthel,

As you noticed it will depend on what the application is. Your question is far to general for a specific answer. Did you have a specific application in mind?
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