How important is shielding?

When making a chassis it seems necessary to make a metal enclosure to shield stray EM radiation. But how bad is this effect? There are quite a few amps that have an acrylic case, like Garage 1217 and Bravo, that are well reviewed and doesn't seem to be an issue. Do they do something special to compensate? Are you just suppose to avoid super noisy environments? Or is it just smart design?

 

The Polaris has an aluminum plate option. I wonder that would have resolved those issues.

 

And what about wood?

 

i had a sansui 5000x in wood case, lot of marantz receivers and power amps used wood cases too. phase linear and even crown used wood cases for home audio stuff. pretty much everything of that era did haha. never had issues. aluminum came around to save money.

on the subject, i think as long as the power transformer is well shielded and the wires inside then it should be no issues what case is used. even the inductors inside act as emi/rf blockers. i mean having wires upon wires in a cluster mess will cause major interference issues. even stupid computer/laptop switch mode power supplies causes annoying squeals...that's why sometimes most issues way solve this is go fully balanced, separate things better with better cable management and decent shielded cable connectors you be good to go.

 

Back in the day, I guess wood must have been the cheapest simplest thing to make cabinets out of. Probably still is for very small runs, but otherwise, wood, these days is the label that says posh.

Back in the same day, I would guess that that interference was much less. I'm sure that the air was, electrically, much cleaner. No mobile phones, not even cordless landlines, no wifi, single-digit numbers of radio and TV stations...

 

From my understanding they weren't really wood. They still had a metal chassis but had an external wooden mount. Here is an example of a crown amp.

http://www.kenrockwell.com/audio/crown/d-150a-series-ii.htm

 

Yeah, these days where your main source is a computer with a bunch of digital noise and then a DAC sitting next to the amp you might need that shielding. Then again I would presume that as long as the DAC and comp are covered in metal then it should be fine. I should experiment with a Magni in the case and then outside the case.