Pizza Box v2.0 Class D amp project

[SoundMods]

Since I have a fire extinguisher nearby and will be putting the amp parts on fire retardant material, it will be fine for testing.

Thanks for the concern, but this is not the first set of power amps in these pizza boxes and had no issues. Last time is was 10 pizza boxes with chip amps boards and linear PS.

10-4

[Pelliott321]

I have had two pieces of electronics mounted in a wooden box for many years now and I am still verticle.
I have a friend in the business and builds all his prototypes on birch ply, do so for over 30 years never an issue, and he told me when he puts the same components in a metal (usually heavy copper), every time he likes the sound of the wood protype better.

[HAL]

There was an article many years back about lining a metal chassis with RF absorption material like carbon loaded foam to lower electric fields in chassis. For magnetic fields mu-metal would help as well around things like transformers or inductors. This was with early CD players and still applicable for digital devices. For RF environments with clock oscillators running makes sense to me.

The foam has to be enclosed so that the carbon does not get onto the circuit board, but should make electrical contact with the chassis. Same hard material use to be used for shipping IC's with the pins inserted for static protection.

Cardboard has the same burn temp as wood or paper and an insulator, so good for temporary testing. Usually falls apart after to many uses as expected.

[tomp]

There was an article many years back about lining a metal chassis with RF absorption material like carbon loaded foam to lower electric fields in chassis. For magnetic fields mu-metal would help as well around things like transformers or inductors. This was with early CD players and still applicable for digital devices. For RF environments with clock oscillators running makes sense to me.

The foam has to be enclosed so that the carbon does not get onto the circuit board, but should make electrical contact with the chassis. Same hard material use to be used for shipping IC's with the pins inserted for static protection.

Cardboard has the same burn temp as wood or paper and an insulator, so good for temporary testing. Usually falls apart after to many uses as expected.

I can see the carbon material working as a short for electric potentials that are in contact with it like IC pins, but I doubt it would have any effect on electromagnetic fields. I have used copper screening to make a Faraday cage to keep out RFI, and that works until the wavelengths involved are smaller than the openings between wires.

[HAL]

The typical material used for RF anechoic chambers is carbon and iron powder loaded rubberized foam. The carbon is for electric field and iron for magnetic field attenuation. Wood is also an E-field attenuator at RF frequencies.

Attenuating the E-Field vector with carbon helps reduce signal propagation. The M-Field needs a ferrous material for attenuation, so adding iron filings or iron oxide to the carbon would be the same. That could be a simple addition to the carbonized foam material and coat with a sealant for protection.

I do not have an EM Field meter to check it for attenuation, but they have gotten pretty inexpensive these days to purchase. Would be hidden inside the chassis so no real impact on look.

Just an idea.

[SoundMods]

There was an article many years back about lining a metal chassis with RF absorption material like carbon loaded foam to lower electric fields in chassis. For magnetic fields mu-metal would help as well around things like transformers or inductors. This was with early CD players and still applicable for digital devices. For RF environments with clock oscillators running makes sense to me.

The foam has to be enclosed so that the carbon does not get onto the circuit board, but should make electrical contact with the chassis. Same hard material use to be used for shipping IC's with the pins inserted for static protection.

I have used carbon loaded foam extensively in digital equipment to prevent radiated RFI from the circuits and clock from being reflected inside the enclosure cavity. The carbon foam absorbs those emissions to good effect.