DIY Active Noise Reduction Headsets

[electriclightfoot]

Could anyone give some advice/instructions on how to convert a passive headset into an ANR headset. As a flying instructor, I've seen a couple of home-made jobbies and would like to have a go myself. I've got around six heasets laying around the house and wouldn't mind sacrificing a few trying.
Cheers
ELF

[Cardinal]

There's a conversion kit for David Clarks and such, some soldering required. http://www.headsetsinc.com/. As for a total do it yourself buildup, I would think you'd need some heavy duty logic/electronics to do the work of ANR. Generating an inverse signal seems simple enough, keeping it exactly in phase seems quite difficult. But I'm a pilot, not an electrical engineer.