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Re: [Phys-l] Why no hum?



I can't believe it -- Well, I'm getting used to it**- As soon as I read hum bucking I remembered. The one my mind's eye's picture is outside of the yoke just underneath the spider.


** If I remember correctly it started about when I was about 68.

bc Die Panzer to Brian W. and remembers it as the h. b. coil.

On 2009, Apr 26, , at 17:31, Brian Whatcott wrote:

Bernard Cleyet wrote:
Back in the middle ages I repaired radios for pin money. The "big"
ones often used a field coil instead of a PM in the loud speaker for
the voice coil "to work against" [correct physics expression]. The
coil did double duty as part of the filter for the HV supply. I
don't remember if they were L or C input filters, but either way I
was surprised -- no audible background hum; still am.

Anyone out there have an idea why.

bc
__
Carr's Old Time Radios! ...

<http://books.google.com/books? id=KkvHhhJcGIwC&pg=PA101&lpg=PA101&dq=field+coil+in+loudspeaker+- +hum&source=bl&ots=gcw4lZ3ZKr&sig=Q47icOXJYINJP8PYWCk3qlGVBdM&hl=en&ei =l_v0ScPaGpTcMbe- sKkP&sa=X&oi=book_result&ct=result&resnum=2#PPA101,M1>

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