Stupid Questions 101

[TwinACStacks]

Pardon My Question but what EXACTLY is the Purpose of the Copper strip/Band You see on some Power Trannys??, Why is it on some and not on others?

Thanx, TWIN

[Structo]

I believe they are called a flux shield or flux band.
It is an attempt at keeping the electromagnetic flux contained to the PT.
Basically another attempt at reducing noise and hum.

[novosibir]

Absolutely correct!

It's reducing the magnetic stray field of the PT

Later the tranny companies often left off the flux band just by economy.

BTW: There are no stupid questions - only stupid answers (sometimes)

Larry

[basisfunction]

Economy was probably part of the reason once they realized a band of copper doesn't do much for magnetic fields that are caused by current sources. A grounded conductor surrounding the tranny will of course shield electromagnetic radiation (Faraday cage) but will do very little to the current source B filed. You need a super high permeability material to "shield" magnetic fields.
If you want to shield magnetic field from current source you have to get serious:
Negate the field by creating an opposing B field, or make a 'flux rejecting' space with high permeability materials. Here's some for you guys if you want to experiment: http://www.mumetals.com/faqs.html" onclick="window.open(this.href);return false;. Mu metal is expensive however and its easier to just move the noise sources as far away as possible, i.e Design the amp right in the first place!