DIY Head Box Question

[Kramer]

Hey all, I got another amp I got done building, and I am about to make a DIY Head Box for it. But, I remember hearing somewhere that you have to put an aluminum plate in it to shield it from outside noise? Can anybody elaborate or confirm this, or have any ideas for that matter? Do you just use aluminum foil like in guitars, or do you need a thicker sheet metal type of plate? Do you just put it in the bottom of the head box, or do you try to shield the top front and sides?

Thanks!

- Alex

[defaced]

http://music-electronics-forum.com/t13750/

That'll hit most of your questions. For thickness, you just need continuity, so thickness isn't an issue. I use a fine wire mesh when I have my amp on the bench. Basically, you're just completing a Faraday cage where the chassis makes up most of it, but you need something to cover the bottom of the chassis to keep radiant electrical noise from entering the amp's cavity.

[Kramer]

This does help quite a bit, but I have a few more questions. Obviously I need to insulate the shield from the amp itself, that shouldn't be too big of a problem, but what exactly is it meant by grounding the foil to the chassis? Surely the foil is not physically connected to the chassis, or how would you be able to get it in and out? Where do you get the shielding, or does it really not matter? Could I just use any aluminum foil from the grocery store and staple it down, or is there some other material I should be using? Thanks for the help!
- Alex

[defaced]

The whole idea is that noise hits the shield, and is directed to ground via a connection between the shield and the chassis (which is at ground potential). Since we're just dealing with stray noise, you don't need a wire or anything, just the fact that the shield will be touching some bare metal part of the chassis will work. For instance, the Mesa Triple Rec I used to own had four screws mounted into the chassis next to the chassis mounting bolts that would dig into the foil shield that was glued into the bottom of the head box. Another example, the Peavey Deuce I have used a chrome chassis, so just that it was touching the file shield worked.

Yes, aluminum foil from the grocery store will work. All you need is something that's conductive and doesn't have big holes in it (hence why I can use tightly woven copper mesh), so the material isn't exactly important.