Came packaged with the press email on Linear Tech's LTC6655 Reference "775nV Noise Measurement for a Low Noise Voltage Reference" by Jim Williams. Application Note 124 -- published in July, but first I have seen it was this evening:
http://cds.linear.com/docs/Application Note/an124f.pdf
Does not specify whether Danish Butter Cookie Tin or Oreos Tin was used for isolation.
http://cds.linear.com/docs/Application Note/an124f.pdf
Does not specify whether Danish Butter Cookie Tin or Oreos Tin was used for isolation.
Look at Figure 3 -- uses an LSK389, but you can use a matched pair of 2sk170s -- the '3581 has a great RMS converter.
Got a whole pile of 2sk170s, not a problem there.
Makes me wonder how Jim Williams gets away with 10,000x amplification of such low noise with the ubiquitous cookie can, thin walled and all, when John Curl was talking with other guys about his need for a thick aluminum case, to keep the noise down to acceptable levels in his Blowtorch preamp.
"Capacitor Dielectric Absorption Requires 24 Hour Charge Time to Insure Meaningful
Measurement. Highest Grade Wet Slug Tantalum Capacitors are Required to Pass This Test"
Now there's something that doesn't cross my mind every day.
Makes me wonder how Jim Williams gets away with 10,000x amplification of such low noise with the ubiquitous cookie can, thin walled and all, when John Curl was talking with other guys about his need for a thick aluminum case, to keep the noise down to acceptable levels in his Blowtorch preamp.
"Capacitor Dielectric Absorption Requires 24 Hour Charge Time to Insure Meaningful
Measurement. Highest Grade Wet Slug Tantalum Capacitors are Required to Pass This Test"
Now there's something that doesn't cross my mind every day.
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Further to your point, the folks from mU Metal suggest that folks who encounter interference problems first try to attack the problem with aluminum foil rather than spending hundreds of bucks on their product. any time you bend or cut muMetal you risk destroying the magnetic properties.
The cookie tin is steel, by the way. I use one for the Uber Oscillator.
I am going to test 6x 220/35V Elna Silk's. I also have some very high quality Spragues and TRW's. No PCB -- but manhattan style construction with Teflon leads.
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Yep, very familiar with the cookie steel box, as I've been using it too for my low-noise amp experiments. In fact my wife gives me strange looks when I reach for the cookie can in the store, as I couldn't care less for sweets or cookies of any kind
Now that escapes me completely. Aluminum is not ferromagnetic at all, so how is it supposed to aid in shielding magnetic fields? Mu-metal is a soft ferromagnet, so copper or transformer iron is for sure closer to its properties than alu.
As copper and transformer iron are hard ferromagnets, their shielding properties for 50Hz magnetic fields are anyway only marginal.
Maybe somebody could point out what I'm missing?
Have fun, Hannes
John is one smart cookie. I've had shielding problems in scientific equipment that could not be solved with thin shielding of any type, including mu metal. It was a magnetic pickup problem and the solution turned out to be a simple plate of 1/2-5/8" aluminum. The field creates eddy currents in the aluminum and the energy is dissipated as heat, but you really need to be up around 1/2" or more before it's really effective.
We have certainly solved the "Pin 1 Problem" with this cookie tin -- I must say that the Costco scots biscuits were much better than Fortnum and Mason:
An externally hosted image should be here but it was not working when we last tested it.
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