[John L Stewart]

What measurable benefit might this copper band have? There is what looks like a connexion to go to ground.

Audiophools bad dream or something new?? Anybody got any ideas??

Cheers to all, John L Stewart

[Peter Wieck]

David Hafler put copper bands on most of his solid state amp transformers. HK did it for some of theirs. Apparently (offered without factual reference) it is a combination shield and hum - audible - damper. It is called a "flux damper", and may be grounded to the secondary, or not.

Hope that helps.

Peter Wieck
Melrose Park, PA

[John L Stewart]

Originally Posted by Peter Wieck

David Hafler put copper bands on most of his solid state amp transformers. HK did it for some of theirs. Apparently (offered without factual reference) it is a combination shield and hum - audible - damper. It is called a "flux damper", and may be grounded to the secondary, or not.

Hope that helps.

Peter Wieck
Melrose Park, PA

Thanx for your response Peter but it is an air cored cross over choke, not a transformer. And the copper band is a right angles to the winding so that coupling would be at a minimum.

We do see Faraday shields often used in PTs to minimize coupling both forward & reverse to the line. I once used a simple piece of steel sheet between at PT & OPT to reduce the incidental coupled hum component. Don't have any numbers on the hum reduction but the audible difference was significant.

Sofar that copper band is a mystery. I guess someone has a reason, we will see!!

Cheers to all, John L Stewart

[Peter Wieck]

John:

Same issue, only more so. A choke, typically, a hot source for stray magnetic fields and an air choke would generate those fields in a fairly predictable manner such that a "flux damper" of a specific configuration might be just the ticket. Tha bean counters have me amplifier real estate too expensive to allow extra space for isolation. This may be an accommodation.

Peter Wieck
Melrose Park, PA

[Peter Wieck]

Perhaps a clarification might be in order. A *speaker* using conventional voice coil and magnet drivers hates stray fields. So, even a choke may need to be damped.

Peter Wieck
Melrose Park, PA