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/showthread.php?postid=1229027#post1229027
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/showthread.php?postid=1229027#post1229027
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.
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.
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.
After much deliberation, I chose a shielded tranny for my B+ circuit, and plain jane split bobbin trannies for all filament and supplementary supplies.
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 🙂
edit- beat me to it, zigzagflux 🙂
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 🙂
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 🙂
zigzagflux said:
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.
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?
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?
ray_moth said:
Some transformers have the high current low voltage heater supply secondary placed between the primary and the high voltage B+ secondary instead of a real shield. Idea was that the heater winding would do almost as good a job of shielding. This winding was usually centertapped, at 3.15V on a 6.3V secondary, and to be tied to chassis ground, like the real shield would have been. The heater winding has to be in the transformer somewhere, and doing it like this instead of a real shield saves a few pennies....
ray_moth said:
IMO it is a big deal, but I understand why some might not thing so.. Compared to a toroid without a E-shield an Ecore transformer is a breath of fresh air. But the Ecore transf. has windings that provide half the benefit of the e-shield IME. Bifilar windings do all of the benefit IME.
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