[time-nuts] Rb references for audiophiles?

Mike Feher mfeher at eozinc.com
Fri Jul 4 21:08:02 EDT 2008


Talking about magnets and skin depth, I recall an incident back in the early
to mid 60's. I was living on Long Island at the time and had many friends
who worked at Brookhaven National Laboratory. Needless to say I had numerous
tours of the facility. At one time I was given a tour of the cryogenic lab,
and was shown a magnet that they were using. To my surprise the magnet was
wound with un-insulated wire. Naturally I had to ask about that, and was
told that at cryogenic temperatures the contact resistance is so much higher
than the actual wire resistance that they do not bother. This way they
claimed they could get more turns on a given solenoid. Another interesting
thing was an LC at cryogenic temperatures. This thing was oscillating on its
own, after it was excited. I guess the Q must have approached infinity with
such a low R. It was interesting. - Mike  

 
 
Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960
 
 
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Lux
Sent: Friday, July 04, 2008 8:57 PM
To: Discussion of precise time and frequency measurement; Bruce Griffiths
Subject: Re: [time-nuts] Rb references for audiophiles?

Quoting Bruce Griffiths <bruce.griffiths at xtra.co.nz>, on Fri 04 Jul  
2008 05:47:53 PM PDT:

> Jim Lux wrote:
>>
>> That one I'm familiar with.. (SpaceWire cables, for instance, have 4
>> shielded twisted pairs, 2 in each direction, with the shields grounded
>> at the sending end for each pair of pairs)...
>>
>>
>> These were just plain old two (gold/palladium plated) pins for each
>> "cable" (granted, the cable is some complex braided combination of
>> silver ribbons, which is a fairly exotic form of Litz wire, I
>> assume... but no shield)
>>
>>
>>
> Unless each individual strand is insulated from all the others (as it is
> in true Litzendraht) braiding the wire is ineffective in reducing skin
> effect.
>
> Bruce

It was unclear from the literature I saw, but I have to assume that  
they know this (Litz wire and all it's properties have been  
"fashionable" in one sense or another for the audiophile biz for  
decades... I had friends who made their own).  On the other hand...


I did run across an interesting product for high end audio (not  
recently)... air core tape wound inductors (i.e. a pancake shaped coil  
with the winding of thin tape, instead of wire) in both silver and  
copper.  Very interesting stuff.   A friend was looking at using them  
for magnets for a rail gun type system (since they have have a hole in  
the middle for mounting)...

Jim


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