Metropoulos Forum

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

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.

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

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!