Well, thanks but it occurred to me that if turntable switching made the sound, putting it on the amp switch wouldnt have any effect, I just failed to think my question through.
Russellc
I have Mu metal for this, but I like Soundhappy's suggestion to ALSO use copper tape. Looking at Edcor's site, many of their transformers come in a shielded version. Poking around, they fully describe the material they use, which is a purpose-made solderable tin plated copper from 3M:
EDCOR - Copper Shielding
Lots of places carry the 3M Embossed Tin-plated Copper EMI Shielding Tape 1345 in various widths and lengths. Not cheap for the continuous rolls, but I think I'm going to try it.
BK
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I WILL use the Mu metal. The 3M tape is extra/easy and routinely employed by Edcor. Belt and suspenders approach, and reversible if it creates a problem.
Can you share your construction method for the shielding box? It looks really great. Sheet metal is a new medium for me.
BK
Can you share your construction method for the shielding box? It looks really great. Sheet metal is a new medium for me.
BK
The shiny box at the rightmost end of the PCB is made of 0.010" Mu-Metal, purchased from McMaster-Carr. Why not use the material you already have?
I traced the flat box on the mu-metal sheet using a thin-tipped Sharpie. I cut the metal using metal snips. I then folded it using a piece of scrap 1/2" square aluminum profile. With a hammer and the scrap aluminum, I made the corners on the sides square. I decided to leave the top corners slightly rounded, but you can use the hammer and scrap to make them square also.
Thank you! Back in February I posted other pictures of the build. You can see them at: http://www.diyaudio.com/forums/pass-labs/281520-official-m2-schematic-72.html#post4975080
Yes, it has to be grounded. In the picture you can see a short piece of green wire below the mu-metal box. It connects the box to the nearest screw holding the PCB to the standoff. And yes, the shield does work.
Change to 6 mA Idss matched LSK | LSJ buffer jfets without 10R's.
Get resistors is more critical in front end gain stage but less in buffer ?
Councils thoughts about eventual parameters of the buffer to take care
and his source resistors influence?
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I didn't ground mine (which was made of copper) but it still works. That's not to say it wouldn't work better if I grounded it though.
Copper will act like a Faraday cage (electric field shielding), but it won't shield anything from a magnetic field.
Copper has a permeability roughly the same as air (~1). Steels are in the hundreds (some getting up to a thousand or so). Mu-metal is in the 10s of thousands.
Grounding will drain off the charge on the surface of a Faraday cage, but the inner and outer surfaces will have opposite charges making them cancel inside the cage anyway. I don't think grounding does anything at all for magnetic shielding.
Cheers,
Jeff.
Copper has a permeability roughly the same as air (~1). Steels are in the hundreds (some getting up to a thousand or so). Mu-metal is in the 10s of thousands.
Grounding will drain off the charge on the surface of a Faraday cage, but the inner and outer surfaces will have opposite charges making them cancel inside the cage anyway. I don't think grounding does anything at all for magnetic shielding.
Cheers,
Jeff.
Antek 400 VA toroids are cool for M2 psu
beacause have magnetic shield incorporated.
http://www.antekinc.com/content/AS-4218.pdf
beacause have magnetic shield incorporated.
http://www.antekinc.com/content/AS-4218.pdf
Absolutely: mitigate at the source with power transformer design/shielding, don't oversize the transformer VA beyond reason, rotate the transformer to find the minimum lobe, maximize layout distance and/or separate enclosure....then worry about the little Edcor with copper flux bands and/or Mu metal enclosure.
BK
BK
Perhaps I should say instead "my amp is quiet", which may or may not be thanks to my nifty little copper boxes.