Thinking of Making A Chassis from Clear Acrylic. Thoughts?

[MadHattter]

I recently purchased a bunch of boards from chipamp.com and am now planning on building the chassis for them. I plan on making three amplifiers, two channels each. All will be mono-block construction. My question is, I am thinking of making one of the chassis - the entire chassis - from clear acrylic. The feet, front panel, rear panel, volume knob, fasteners (if used instead of cement) everything . . .

So, am I going to have EMI / RF issues by not using a metal enclosure?

Would a star ground be all I need?

I guess I should ask, is there something else that I would have to do differently?

Thanks.

[djQUAN]

not exactly your size requirements but I have made one in the past without much problems. Hopefully, you might get an idea or two from it.

Mini Test Oscillator

[GloBug]

Mock it up in cardboard first just to make sure. If you use a star ground and shielded signal cables you should be OK.

[GloBug]

Higher quality window tint uses metallic particals rather then dye, it's know to cause poor radio and GPS reception in some cars.

Glass and tint could be a plan "B".

[diarav]

I am planning to use Acrylic too. I might suggest you use a metal base - I have mounted the TFR and AMPs with Heatsink on the metal base.

[AndrewT]

Originally Posted by MadHattter

.............. am I going to have EMI / RF issues by not using a metal enclosure?

Would a star ground be all I need?

I build all my amplifiers up in an experimental form without any case/chassis.
I have never found any power amplifier to be quieter after installing it inside a metal chassis.
Are there any exposed conductive parts?
That answer will determine whether you need to connect those parts to Safety Earth and determine what you do with the PE (third wire in the mains cable).

[Leglandu]

I made a wood + altuglass (plexiglass ?) chassis for a LM3875 AudioSector kit and unfortunately I got a strong noise from a DETC phone and also a nice FM radio although not the right one

First, I shielded all signal cables but nothing improved !

FM radio was just fixed by adding an RC filter at input and 300pF at chip legs.

For the telephone noise, I had to shield the entire box, including base and top, with a self-adhesive aluminum tape. It is hard to do after the amp is done and all the bands must be connected to the main ground, but happily it handled ~98% of the problem.

Now, next amp will have a wood chassis too as it is so easy to work and modify. But sure I will use the aluminum tape before installing electronics parts !!!

Aluminum tape is used for connection of the panels of insulation under roof

Edit : oups, sorry MadHattter, I realise the aluminum is not really 100% transparent...

[AndrewT]

How can you connect permanently to the Al tape?

[marce]

Refer to this site, and if possible his book 'Electromagnetic Compatability Engineering' it is the definitive tome on solving these sort of problems (pages 116-140, covers various grounding schemes).

http://www.hottconsultants.com/

If you want to put PCB's in unshielded plastic boxes then for RF immunity the EMC protection has to start at board level and realy requires ground planes.

Oh and Keith Armstrong, Tony Waldren articles from this site:
http://www.compliance-club.com/

[Leglandu]

@AndrewT : by including silver plated cables, under an aluminum "patch". And also, at bottom, plated by the brass screw with broad head of the main ground... the same into the amp.