New Screening/earth design/prosject

[microc]

Hi peeps!

Because of some earth problems and some humming with my projects I've been working on some new screening/earth design.

I'm going to make a new Hi-Fi tube amp from Andrea Ciuffoli www.audiodesignguide.com to test out my design, if some of you agree to this design.

I'm thinking of making a chassis of 3 mm alu with 4 different "rooms"; I know, this is not "new" design. But if I make 4 copper boxes that fits inside the alu chassis room, but no contact with the aluminium (I gonna use rubber feet or liquid rubber to seperate alu "rooms" from copper "rooms". 4 seperates room for: Amp circuit, 2 rooms for each output transformer and the last room for a psu circuit.
I will connect the 4 copper boxes together.

Now: Should I use the copper as earth, or should I use the alu chassis?

Any thoughts what so ever?

Is this done before?

 

[strangeandbouncy]

Hi,



  I am not much of an expert, but I am certain that proper layout/design/best practice should SURELY be easier and more effective? Looks like a sledgehammer to crack a walnut to me. I have built many projects with scant regard to much best practice( I do try to mount mains transformers in another case outside if possible). None of my projects are noisy/hummy, and I am very discerning, believe me.


      Just my pennyworth,



        ANdyP

 

[sahib]

Are you sure you are making a case to house an amplifier and not to store nitroglycerine? This is taking the Faraday cage into extreme. You don't get that sort of EMI protection even in the scopes that operate at GHz levels.

Making seperate compartments out of aluminium is already overdoing it, but if you insist that is fine. Just pay attention to wiring layout.

 

[microc]

well, "sledgehammer to crack a walnut" would describe it  ;D
It's just something I would like to try, and also to see the differens of using the copper as earth vica alu as earth. I got the idea from military minehunting vessels, where the EMC are very restrict.

Maybe I will scale it down to just screen out the psu transformer then..

 

[abbey road d enfer]

The valuable concept in there is the use of non-ferromagnetic metal, which avoids the bad surprise of stray fields going where they are the most noxious, and limits circulation currents in the chassis.
Regarding which - copper or alu - to use as ground, it is clear that copper, having the lowest resistance, is the best.
This should be done in accordance with good practice, which is minimising inter-stage ground resistance; that means the connector-to-preamp ground must be as short and stiff as possible, as should be preamp-to-power amp, and power amp-to-PSU.