These are new...Do they work? Choked chokes!

[jeffdavison]

Inquiring minds want to know!

actually not choked, but shielded....

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... Track=true

do unshielded chokes really cause hum? induced or otherwise?


JD

[mesherm]

The shielding may improve the heat dissipation. I have packed unshielded C354 chokes in the darndest places and haven't noticed any extra hum or noise. The push pull section connected directly after the choke in the power supply is inherently immune to common mode ripple and noise. My experience is that 99% of all the hum and noise problem can be eliminated by careful attention to grounding schemes, wire dressing and input cable placement.

[erichayes]

Hi All,

Whether a choke will hum, or cause hum depends largely on its application, Jeff, but a poorly made choke will hum louder than a well made one.

A choke is most likely to buzz in a choke-input filter. This is because the laminations are being subjected to the huge rising and collapsing field being created by the pulsating DC coming off the rectifier. In a cap-input filter, the amount of ripple seen by the choke is in the order of 15 volts or less. The more ripple voltage and current the choke has to deal with, the more tendancy it will have to radiate hum, so physical placement definitely needs to be considered.

A good EI laminated inductor will be vacuum-impregnated with varnish and baked to keep the laminations from vibrating, or, in the case of output transformers, "singing", but nothing works perfectly. All of my 1773 amplifiers have a characteristic "TWAAANG!" when first turned on, caused by the choke suddenly saturating.

[Uncle Ned]

Inquiring minds want to know! actually not choked, but shielded....do unshielded chokes really cause hum? induced or otherwise?
JD

The shields certainly don't hurt anything, and they don't cost any extra.

Also, the choke looks a lot nicer if you need to mount it above the chassis for some reason.