how do i test for mu metal

[seavote]

i have some covers from some large transformers that came out of a tube rf amplifier. i saved them thinking they may be mu-metal and i could use them to make up sheilding in a hamptone lcmp tube pre. is there a test i can do to determine if these covers are indeed mu metal. cant seem to find anything on the web. thanks

 

[CJ]

bar room test, stck a magnet to it, measure the pull vs cross secvtional area in cm^2 for gauss, in^2 for tesla...

 

[seavote]

is there a way to do this without a gaussmeter? something more bar room, maybe the bar room floor method?

 

[clintrubber]

[quote author="CJ"]happy ****** birthday all yuou mutha fuckers i made it to
whatever

1-22-55 corresponds too and no, i dont expect bno happy responses so **** you in advacveace all you useless mutha fuckers that I love so much!!!


:sam: :sam: :sam: :sam:[/quote]
What you, get lost yourself, you were born on 12-24-1945...
but if that happens to be in error then enjoy yesterday :sam:

 

[CJ]

Run for your Life!
The ocean is rising!

But I have Kayak loadd with V 76 input iron.

 

[Guest]

[quote author="CJ"]

wonder what a mic pre input ribbbon transformer made out of schick razor blade lams would sound like?


might be a new patent....
ok so no wonder i am whacked,


:sam: :sam: :sam: :sam:[/quote]


Once trying to disassemble a single cylinder motorcycle motor I stuck a screwdrivers into a hole for carburetor, turned a wrench, and.. Cfrrrrack! -- broke a part of a piston. What to do, how to fix?
Nada, go forward, go for it!
I took a peace of a coppered fiberglass I used to etch PCBs, cut a rectangular hole in it, and soldered a peace of a razor blade as a tongue type valve, put such a valve between cylinder and carburetor and got a supercharged motor.
Later I had to glue by epoxy between fins additional poles made of thick aluminium wire, about 1/4 inch diameter. It looked like a hedgehog, but run very fast consuming fuel and oil mix like a drunkard.

 

[CJ]

OK.

very extremely ingeniuus herr mc giver red valve guy but beet this;
I wa cruisin, stoned out ofmy mind and obviusly paranoid of courdse, have you ever bee up the Panimint Pass in Death Valley, cut across shorty cut aross, I brokedown thrre ein a 60.5 Volvo 12 S Black 43 door sedan, and all you hippies who know Volvos frfrom way back know hat Im talikni about,
122 s, 1444 bathtub, the weierd sports vcar that I love so much,

you know,


and this is sometimgningh that has taken me years to learn, Cars make a big differencence in yuour life, you can cruiise Death Valley in a busted up Volvo with leaky SU carbs, but WTF< gas is only 75 cents

we are screwedede!

 

[rafafredd]

there was a way with easy to find chemicals...

 

[PRR]

> is there a test i can do to determine if these covers are indeed mu metal.

Who the hell cares what they are made of????

Set up a live power transformer, and a small naked audio transformer. Measure the hum. Put a beer or cat-food can over it and measure again. Try steel. Try aluminum. Try your ??-metal can.

If the hum is less, you don't care what the stuff is.

Oh: totally closed can is best, but if the distance from open end to "mike transformer" is bigger than the opening, it gets nearly as good as totally-sealed. Which means a cat-food can is probably no good (wide and shallow) but a beer-can (or radio IF can) is good enough to estimate the effect of the metal.

Hum should be "small". If you are getting volts of hum, the magnetic field is so strong that true Mu-metal will saturate. Rational mike-amp design starts with keeping mike-tranny far away from all hum sources; distance is your best shielding per dollar. Then you may want a layer of plain-iron: it will knock-down higher fields than Mu can stand. Mu is only for getting from "small" to "very small".

> Volvo 12 S Black 43 door sedan

You just made that up. Volvo has never produced a 43 door sedan.

You either mean the '40 Ford-sh PV, or the Kaiser-ish Amazon.

One of these parks at work most days:

 

[seavote]

thanks PRR. will do. as you can see after you suggested i try the hamptone HVTP2 (in another thread)i went and complicated things by going with the LCMP . no longer sold as a kit, no parts list and no pcb available. i have a small project studio where i record mostly myself and sometimes a few friends. it would be tough to justify the $900 investment (although i know its dirt cheap for the end product i would be getting) with the scores of other bills i now have. i can get 2 channels of the lcmp built for about $400- $500 with all the suggested upgrades. i went with the pre made power supplies and i will be mounting them in a separate enclosure so the power supply can be kept away from the audio signal.i have the basic layout (psu) planned. but i could use some suggestions as to the best way to get the power from the psu enclosure to the pre amp section. best connector to use, what type of cable? i have all the components for putting the psu together except these two parts. thanks for any suggestions.

 

[seavote]

i thought i had read this but couldn't find it again. just found it now.

http://www.hamptone.com/sepbox.htm
i'll use 5 pin xlr,4 wire cable with sheild and hard wire the psu end.

 

[Freq Band]

Measure the hum. Put a beer or cat-food can over it and measure again.

remove original contents first.

...or it will sound like a drunken cat.



Who sells xformer shields, besides Purina ?



=FB=

 

[zapnspark]

Electronic Goldmine has some mu metal sheets.
http://tinyurl.com/ysfkjx

ZAP

 

[Freq Band]

Except bending and forming MU metal causes it to lose it's spiritual properties.
I wonder if it can be welded at the cut seams, by a DIYer at home.
I have some empty plug-in module cases of MU-metal, and they have nicely welded/soldered seams.

=Fook Band=

 

[zebra50]

With a good iron, one certainly can solder mu-metal - I've done this in the past. Whether one should and if it theoretically degrades the shielding properties, I know not.

In practice, I found it still acted as a useful shield.

 

[gyraf]

[quote author="zapnspark"]Electronic Goldmine has some mu metal sheets.
http://tinyurl.com/ysfkjx

ZAP[/quote]

at only 10$/sheet, it's a Very good price, imo! (well, unless it's ultra-thin - thickness is unspecified). Going rate is around $200/kilo for mumetal these days..



Jakob E.

 

[mr coffee]

It's pretty thin.

Think thin sheet of paper from one of those old thermal fax machines.

But it is nice for some things like low noise transformers.

CJ,

Damn you. I've know I've gotta see Death Valley now.