Shielding DACs : any tips about materials?

Eldam · 2014-09-03 5:02 pm

Hi,

I was askink myself if there is a minimum thickness for aluminium or iron case for a passive shielding in town & home environment (EMC, celular waves...) for casing our DACs and their PS (in their own case ?)

What about proofing : I mean I see most of the off shelves CD players have front and back in plastic and some open hole in the iron case below for the heat ?

JP fellow gave me a good hint about switchs network case for IT infrastructures : we can mean than if good enough for networks datas it's good enough for casing our dacs... and second hand case are good for the bucks and our planet also !

I saw also light aluminium flan case for uniq cooking use ! thick enough.

All those shielding needs some light polarisation for higher sheilding ?

sesebe · 2014-09-03 9:45 pm

Hi,

For my DAC I use a case made from 0.5mm steel reused from a internet switch.

I made some tests and with a cell phone during calls placed on the box I could not hear any noise from phone.

jean-paul · 2014-09-03 10:03 pm

Good test !

Eldam said:
Hi,

I was askink myself ...

I watched Allo Allo so I had to chuckle. I am Eldam from le french restistens and I will say this only once

marce · 2014-09-04 5:15 pm

Shielding and screening is fun, and more complex than many realise, slots and seams being items of major importance when trying to shield equipment. But a metal case is always a good place to start.

Allo Allo ran from 1982, gawd I feel old I can remember watching it when it first came on as a young enthusiastic 21 year old, like Dads Army classic comedy.

Willi Studer · 2014-09-04 5:23 pm

Steel has the best shielding properties (not sure about lead) and the most impermeable Faraday cage is plain sheet, so no holes or grilles. Since dimensions and weight are not crucial in your design, I would go for 0,5 to 1 mm steel sheet enclosure or assembled panels. As shield collects outside EMI, it is important to properly earth or ground it.

Speedskater · 2014-09-04 5:30 pm

While steel has shielding advantages at low frequencies, at high radio frequencies copper & aluminum have the advantage.

Mother Earth has nothing to do with shielding.

Eldam · 2014-09-04 5:36 pm

jean-paul said:
Good test !

I watched Allo Allo so I had to chuckle. I am Eldam from le french restistens and I will say this only once

Don't know "Allo Allo", we are not english dutch here ! What is the reference, before I could understand when you linked

Surmise we could do together a good chuckle band

: BOM-Knight & the Cococnuts-Checker :rofl:

Well I'm here to go further than your hint about old IT switch-case as I haven't nowadays for free...

Thank you my papy JP for intellectual coaching

Eldam · 2014-09-04 5:40 pm

sesebe said:
Hi,

For my DAC I use a case made from 0.5mm steel reused from a internet switch.

I made some tests and with a cell phone during calls placed on the box I could not hear any noise from phone.

thanks, Yes that was that JP hinted to me, but unluckily have not anymore such cases... a pity as before I had a lot in
my job ! But was involved to try to trhink by myself to others things as IT manager....

... but where this RJ45 go onto this SPIDF plug :scratch1:

as JP testimonied about my own capacity

Eldam · 2014-09-04 5:44 pm

marce said:
Shielding and screening is fun, and more complex than many realise, slots and seams being items of major importance when trying to shield equipment. But a metal case is always a good place to start.

Allo Allo ran from 1982, gawd I feel old I can remember watching it when it first came on as a young enthusiastic 21 year old, like Dads Army classic comedy.

thanks Marce,

Is there a minimum thickness to such case where below it's no worth to use it ? Are the open metal box (with front & back in plastic) useless ?

OK understand now... Allo Allo is for the guys born during the Second WAR... I'm a little younger... just 45 -

Hé read you advance in your photograph project with plants ! Do you use manul focuse with multiple rapid shoot to have a 3D macro after software treatment ? Nice ! Ah vous les anglais et les plantes... !

Eldam · 2014-09-04 5:49 pm

Speedskater said:
While steel has shielding advantages at low frequencies, at high radio frequencies copper & aluminum have the advantage.

Mother Earth has nothing to do with shielding.

Does the both need to be involved in our DIY DAC ? Steel case & light aluminium around the pcb (not touching it) with hole for heat e.g. ?

Or the simplier, the better : just a steel case, à la old CD player took from the gardbage: i.e.: à la Green Earth French resistent !

Willi Studer · 2014-09-04 5:50 pm

Speedskater said:
While steel has shielding advantages at low frequencies, at high radio frequencies copper & aluminum have the advantage.

Mother Earth has nothing to do with shielding.

You may be right, although most of RF cables I have seen have had steel shields. Regarding the grounding, how do you eliminate AC voltage potential induced in the shield?

Speedskater · 2014-09-04 6:11 pm

How do they do it in an airplane?
With a good shield system, all the interference stays on the outside of the shield.
And no most shield don't do much shielding with low frequency magnetic fields but that's not about Mother Earth either.

jean-paul · 2014-09-04 6:48 pm

Eldam said:
.. but where this RJ45 go onto this SPIDF plug as JP testimonied about my own capacity

Hi Eldam, I am sure you are creative enough to mount a round connector in a square hole

As said, just have an aluminium sheet cut as a new cover, screw or glue it to the case. Now drill the necessary new holes, deburr them (you could use a much bigger drill and turn it by hand in the hole to deburr) and clean the case with thinner or the like, sand it with fine sanding paper when necessary but take care not to sand covers that have "relief" or some kind of pattern on them. Clean it again, paint it with good grey primer (thin!) and then paint it with matte or satin black epoxy paint. Don't use acryl paint. You will regret using cheap acryl paint from supermarkets as it comes off when you take the device out of the audio rack etc. If you like I can make some pictures from some of my "creations". Very old cases from the seventies are the best when they're not corroded. A lot of attention was given then to sturdyness/longevity. However the bottom cover often is treated with cadmium which should not be sanded as its dust is very detrimental for your health !!! It has a typical yellow/greenish oil like shine.

Hardest part is to have the boards and PSU in the case with all wiring optimally placed and this also counts for 230 V inlet, SPDIF, switches, power LED etc. Think first, make a drawing, put the boards loose on a sheet of paper (to avoid scratches) in the case and try to imagine how it will look. Try to go for AC as far away as possible from audio and shortest possible wiring. Check your other equipment if the PSU is located on the left or right side of their cases. It is good practice to go for a standard, so either left or right depending on your other stuff. In case your devices will be placed on the same surface it can be OK to mount the transformer on the left when the other device has the transformer on the right. It will have lowest stray fields and input/output wiring will be tidy and close to the connecting side of the other device. Think about that.

Print this out and attach it to your audio working desk

I am quite sure you will have a different view on for instance an old metal cased car battery charger that you want to throw away from now on...

Eldam · 2014-09-04 7:06 pm

thank you guys for your inputs. Have to go with the tools now !

marce · 2014-09-05 9:48 am

Eldam · 2014-09-05 2:16 pm

tHANK YOU VERY MUCH MARCE,

Since you give us didactic links, I maid a folder named "Layout"

Well D800 is more than a serious shooter !

I don't now all the technics to add artificial deep field on the photographs but the multiple rapid shoots with a manual focusing mvt with the lense and after the merge of the files in such software : StereoPhoto Maker (English)

I still have my old manual argentic Balda for street photography & family pictures... but would like to go to a "not" too expensive Fuji CMOS à la XM1 or XE2 when we will travell again... Liked some years ago the mini travel shooter like the little Sony... Younger I travelled in some countries like China, India or Indonesia with 3 k of material to photograph + my Bag-Pack

... Never again !

Shielding DACs : any tips about materials?

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