Cryo Dipping

[west]

There seems to be a new craze on some glass NGs regarding sending your tubes
to be dipped in liquid nitrogen (absolute zero). The praises sung after
having this procedure are not subjective, but an order of magnitude positive
improvement in just about all aspects of the sound. Some are sending out
their entire collection of glass to be "dipped."
I'm wondering if anyone here has heard of this and what is your opinion
and/or experience?
Cordially,
west

[TubeGarden]

Hi RATs!

As a kid, I spilled a beaker of boiling water on my left shoulder. The Dr.
treated the scars with liquid Nitrogen. My left shoulder sounds much better
than my right.

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

[Ian Iveson]

Be smug if you like...you obviously don't know much about space
domain boundary alignment.

I had an old Mullard double-getter that showed double lines on a
tracer. Explain that if you can.

The ambience of the valve factory, which normally dissipates and
oxidises in air under UV, gets sealed into the valves, where it is
preserved in the structure of the vacuum. So Monday morning valves
sound keen, Tuesday afternoon valves sound glum, and Friday valves
just don't care any more. My old EL84 was Wednesday after the pub I
guess.

Cryogenics is a blunt instrument that drains the happy spirits along
with the malevolence. Better to have them blessed by a Catholic
bishop.

cheers, Ian

"TubeGarden" > wrote in message
...
> Hi RATs!
>
> As a kid, I spilled a beaker of boiling water on my left shoulder.
The Dr.
> treated the scars with liquid Nitrogen. My left shoulder sounds
much better
> than my right.
>
> Happy Ears!
> Al
>
>
> Alan J. Marcy
> Phoenix, AZ
>
> PWC/mystic/Earhead

[Lord Valve]

west wrote:

> There seems to be a new craze on some glass NGs regarding sending your tubes
> to be dipped in liquid nitrogen (absolute zero). The praises sung after
> having this procedure are not subjective, but an order of magnitude positive
> improvement in just about all aspects of the sound. Some are sending out
> their entire collection of glass to be "dipped."
> I'm wondering if anyone here has heard of this and what is your opinion
> and/or experience?
> Cordially,
> west


Is there any hard science on this? BTW, liquid nitrogen isn't anywhere
*near* absolute zero. Liquid helium is close. Reminds me of an ad
I saw once in a music industry magazine about some cryo-treated
bass strings. They claimed to treat them at ONE MILLION degrees
below zero. I sent them a letter (this was back in the snailmail days
gently pointing out that absolute zero was about -460 degrees F,
and that it was impossible to go any lower. Never heard back from
them.

Wonder why...???


Lord Valve
Curious

[Henry 007]

>
> Is there any hard science on this? BTW, liquid nitrogen isn't anywhere
> *near* absolute zero. Liquid helium is close. Reminds me of an ad
> I saw once in a music industry magazine about some cryo-treated
> bass strings. They claimed to treat them at ONE MILLION degrees
> below zero. I sent them a letter (this was back in the snailmail days
> gently pointing out that absolute zero was about -460 degrees F,
> and that it was impossible to go any lower. Never heard back from
> them.
>
> Wonder why...???
>
>
> Lord Valve
> Curious

Well the hard science would tend to suggest that the innards of the tube may
not even get *that* cold at all- a vacuum is a pretty good insulator. So I
suggest that this is another "audiophool" fad, like raising your cables off
the floor or putting CD's in the freezer.

[Ross Matheson]

I do like the notion that -40 deg is unambiguous in Fahrenheit or Celsius.

: Lord Valve
: Curious

Ross Matheson
Islander:=})

"Heavier- than- air flying machines are impossible."
- Lord Kelvin, President, Royal Society, 1895.

"Radio has no future."
- Lord Kelvin, Scottish physicist, 1897.

= =

"If it can't be done, it interests me."
- Joseph Newman.

"... after a few more flashes in the pan, we shall hear very little more of
Edison or his electric lamp. Every claim he makes has been tested and proved
impracticable."
- New York Times, January 16, 1880.

[Mark Harriss]

> Cryogenics is a blunt instrument that drains the happy spirits along
> with the malevolence. Better to have them blessed by a Catholic
> bishop.
>
> cheers, Ian


I still reckon you can't beat the sounbd of casting them in
concrete using a tub of youghurt for a mould

[Lord Valve]

Henry 007 wrote:

> >
> > Is there any hard science on this? BTW, liquid nitrogen isn't anywhere
> > *near* absolute zero. Liquid helium is close. Reminds me of an ad
> > I saw once in a music industry magazine about some cryo-treated
> > bass strings. They claimed to treat them at ONE MILLION degrees
> > below zero. I sent them a letter (this was back in the snailmail days
> > gently pointing out that absolute zero was about -460 degrees F,
> > and that it was impossible to go any lower. Never heard back from
> > them.
> >
> > Wonder why...???
> >
> >
> > Lord Valve
> > Curious
>
> Well the hard science would tend to suggest that the innards of the tube may
> not even get *that* cold at all- a vacuum is a pretty good insulator. So I
> suggest that this is another "audiophool" fad, like raising your cables off
> the floor or putting CD's in the freezer.


Yes, but the innards aren't thermally isolated from the outards. ;-)
(If the tube gets hot on the outside, it'll certainly get cold on the
inside.) It might take awhile for everything in the tube to get as
cold as it can, though. How long do they dip 'em for?

Never heard about putting CDs in the freezer. The stuff I listen
to is so cool to begin with, it probably wouldn't make any difference.

Now that you mention it, I do seem to recall something about putting
cables in the air, and some little ceramic"stands" that were sold
for the purpose. There is probably a *tiny* bit of science behind
that, since if the low-level signal cables are microphonic, there
could well be some sort of acoustic feedback path through the
floor. You'd have to be playing your system *punishingly* loud
before this effect would show up, I would think. We do see this
effect a lot with guitar rigs, where cheap cables make slithering
and thumping noises when moved around onstage. The better
cables have triboelectric shields (Canare, Belden, etc.) to keep
this from happening.

Lord Valve
American

[Lord Valve]

Ross Matheson wrote:

> "... after a few more flashes in the pan, we shall hear very little more of
> Edison or his electric lamp. Every claim he makes has been tested and proved
> impracticable."
> - New York Times, January 16, 1880.

Jeez, the NYT was fulla **** even 123 years ago.How 'bout dat. ;-)
LV

[Choky]

my Metallica CD is best when is in freezer;
(not in CD player ;)
hiya Tim,ya RAO lover!

--
Choky
Prodanovic Aleksandar
YU


"Henry 007" > wrote in message
...
>
> >
> > Is there any hard science on this? BTW, liquid nitrogen isn't anywhere
> > *near* absolute zero. Liquid helium is close. Reminds me of an ad
> > I saw once in a music industry magazine about some cryo-treated
> > bass strings. They claimed to treat them at ONE MILLION degrees
> > below zero. I sent them a letter (this was back in the snailmail days
> > gently pointing out that absolute zero was about -460 degrees F,
> > and that it was impossible to go any lower. Never heard back from
> > them.
> >
> > Wonder why...???
> >
> >
> > Lord Valve
> > Curious
>
> Well the hard science would tend to suggest that the innards of the tube
may
> not even get *that* cold at all- a vacuum is a pretty good insulator. So I
> suggest that this is another "audiophool" fad, like raising your cables
off
> the floor or putting CD's in the freezer.
>
>
>
>
>
>
>

[Adam Stouffer]

west wrote:
> I'm wondering if anyone here has heard of this and what is your opinion
> and/or experience?
> Cordially,
> west

I should start buying liquid nitrogen.


Adam

[Ross Matheson]

Lord Valve > wrote:

: Ross Matheson wrote:
:
: > "... after a few more flashes in the pan, we shall hear very little more of
: > Edison or his electric lamp. Every claim he makes has been tested and proved
: > impracticable."
: > - New York Times, January 16, 1880.
:
: Jeez, the NYT was fulla **** even 123 years ago.How 'bout dat. ;-)
: LV

Well, I don't know who wrote it:-)}
Could jest be speckles of ****e~
Yin-Yang, you know?

Source was :=
http://www.padrak.com/ine/FABFACTS.html

[Rich Andrews]

Bob Hedberg > wrote in
:

>
> Well, I did have my eardrums and the small bones from my inner ear
> dipped in liquid nitrogen, and also had my semicircular canals flushed
> out with liquid nitrogen. It seems to have improved my hearing
> remarkably. I can now hear things which aren't even there!
> The timbre and pace of the micro-dynamics involved with beating old
> cans with large soup spoons is now correct. It's a wonderful thing.
> ; )
>
> Bob Hedberg

In general, it is not a good idea to do what the voices in your head tell you
to do. (:>)

r

>
> "west" > wrote:
>
>>There seems to be a new craze on some glass NGs regarding sending your
>>tubes to be dipped in liquid nitrogen (absolute zero). The praises sung
>>after having this procedure are not subjective, but an order of
>>magnitude positive improvement in just about all aspects of the sound.
>>Some are sending out their entire collection of glass to be "dipped."
>>I'm wondering if anyone here has heard of this and what is your opinion
>>and/or experience?
>>Cordially,
>>west
>>
>>
>
> Bob H.
>
> Just grab that plate in one hand, the chassis in the other,
> and FEEL the power of tube audio!!!
> (not literally, of course, just kidding. DON'T DO THAT!)
>
>



--
"Any sufficiently advanced technology is indistinguishable from
magic."

Arthur C. Clarke (1917 - ), "Technology and the Future"

[Rich Andrews]

Adam Stouffer > wrote in
:

> west wrote:
>> I'm wondering if anyone here has heard of this and what is your opinion
>> and/or experience?
>> Cordially,
>> west
>
> I should start buying liquid nitrogen.
>
>
> Adam
>
>

It is a helluva way to make Ice Cream. Not necessarily economical, but you
can whip up a batch in just a few minutes.

r


--
"Any sufficiently advanced technology is indistinguishable from
magic."

Arthur C. Clarke (1917 - ), "Technology and the Future"

[Robert Casey]

west wrote:

>There seems to be a new craze on some glass NGs regarding sending your tubes
>to be dipped in liquid nitrogen
>
I had my eyes cyro'ed some years ago, and it kept me seeing....
(Retina detachment repair: Doctor uses liquid nitrogen to create a
controlled frostbite
injury on the eyeball near where the detachment is, and scar tissue
forms as it heals
grabbing and locking down the retina. He also used a "scleritical(sp)"
buckle around
the eyeball to squeeze it some. ).

[Robert Casey]

>
>
>
>Now, if they could only do ear implants, I would like a few more octaves...
>
>
>
We would insist on vacuum tubes in ear implants, or at least no
op-amps.... :-)

[TubeGarden]

Hi RATs!

Ear implants, to be acceptable, must be passive devices, like the plastic
eyeball lenses :)

Bit trickier, technically.

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

[Lord Valve]

Ken Gilbert wrote:

> "west" > wrote in message >...
> > There seems to be a new craze on some glass NGs regarding sending your tubes
> > to be dipped in liquid nitrogen (absolute zero). The praises sung after
> > having this procedure are not subjective, but an order of magnitude positive
> > improvement in just about all aspects of the sound. Some are sending out
> > their entire collection of glass to be "dipped."
> > I'm wondering if anyone here has heard of this and what is your opinion
> > and/or experience?
> > Cordially,
> > west
>
> well, as one who has actually heard cryoed tubes, i can answer your
> question honestly.
>
> YES i can hear a difference. a bit smoother, and less microphonic.
>
> this is in a very high gain 500w guitar amplification rig. i built it
> myself, and i am very in tune with how it sounds.
>
> before you say i heard a difference because i wanted to, or i thought
> i did, after i paid all this money for it, i will simply reply that i
> did not mark the tubes in any obviously discernable way--i put them in
> a big box with other tubes of exact same mfg. and type, and can pick
> them out every time. and i didn't pay a cent for 'em to be treated.
>
> it's not that expensive. try it yourself and make your own decisions.
>
> jm2c
> ken


Anyone have any technical details on the process? I mean, liquid
nitrogen is pretty cheap (you can get it at most welding supply
joints) and easily handled (styrofoam cups, thermos bottles,
etc.) so it'd be easy enough to experiment with. How long
do you have to cool 'em for? Any precautions? Etc....

Lord Valve
Curious

[Russ W. Knize]

On Thu, 07 Aug 2003 03:55:28 -0500, Tim Williams wrote:

> "Lord Valve" > wrote in message
> ...
>> Anyone have any technical details on the process? I mean, liquid
>> nitrogen is pretty cheap (you can get it at most welding supply
>> joints) and easily handled (styrofoam cups, thermos bottles,
>> etc.) so it'd be easy enough to experiment with. How long
>> do you have to cool 'em for? Any precautions? Etc....
>
> Well it can't be too easy since dropping a room temp tube into a cup
> of LN is like putting a fresh-from-the-amp 6L6 in a bath of ice water.
> Can you say *crack*?

Perhaps a little prep in the deep freeze? Even then, the differential may
be too much. Hovering the tube over the liquid in an insulated
environment might be good enough to bring the tube closer to the liquid's
temp before immersion.

Russ

[Lord Valve]

Russ W. Knize wrote:

> On Thu, 07 Aug 2003 03:55:28 -0500, Tim Williams wrote:
>
> > "Lord Valve" > wrote in message
> > ...
> >> Anyone have any technical details on the process? I mean, liquid
> >> nitrogen is pretty cheap (you can get it at most welding supply
> >> joints) and easily handled (styrofoam cups, thermos bottles,
> >> etc.) so it'd be easy enough to experiment with. How long
> >> do you have to cool 'em for? Any precautions? Etc....
> >
> > Well it can't be too easy since dropping a room temp tube into a cup
> > of LN is like putting a fresh-from-the-amp 6L6 in a bath of ice water.
> > Can you say *crack*?
>
> Perhaps a little prep in the deep freeze? Even then, the differential may
> be too much. Hovering the tube over the liquid in an insulated
> environment might be good enough to bring the tube closer to the liquid's
> temp before immersion.
>
> Russ


I reckon you could put the pins into the LN and let it suck the
heat outta the tube first, eh?
LV

[Chuck Harris]

Hi Al,

To be a tube cracker is one thing; but
apparently to be a crackpot is your thing.

Personally, I think that cryo treatment of
tubes will give the tube glacial lows, and
frosty highs. Should be very refreshing to
hear on a hot summer day.

-Chuck

TubeGarden wrote:
> Hi RATs!
>
> So we crack a few tubes. It ain't the end of the world.
>
> Good thing not everyone is prevented from action by theories of potential
> disaster.
>
> It's amusing to see those who are trying to warn the rest of us :)
>
> "The sky will fall! The sky will fall!"
>
> Phooey.
>
> Happy Ears!
> Al
>
> PS Your best post to date, LV ;)
>
>
> Alan J. Marcy
> Phoenix, AZ
>
> PWC/mystic/Earhead

[TubeGarden]

Hi RATs!

Yup. The pot may be cracked, but the chili is good :)

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

[Robert Casey]

TubeGarden wrote:

>Hi RATs!
>
>So we crack a few tubes. It ain't the end of the world.
>
>
>
You could practice on "spent" junk tubes first. Once you discover a
dependable
way to avoid disaster, then move on to the good tubes.....

[Robert Casey]

Ken Gilbert wrote:

>"west" > wrote in message >...
>
>
>>There seems to be a new craze on some glass NGs regarding sending your tubes
>>to be dipped in liquid nitrogen (absolute zero). The praises sung after
>>having this procedure are not subjective, but an order of magnitude positive
>>improvement in just about all aspects of the sound. Some are sending out
>>their entire collection of glass to be "dipped."
>>
>>
>well, as one who has actually heard cryoed tubes, i can answer your
>question honestly.
>
>YES i can hear a difference. a bit smoother, and less microphonic.
>
>
>
Anyone have an explanation as to why it should matter if the metal in
the electrodes
has one crystal structure vs another? Aside from the cathode, all that
should do
anything is the physical spacing of the cathode, grids and plate. As
long as the grids and
plate are made of conductive metal, the electrons shouldn't care if the
grid is made
of copper, iron or gold. The metal is likely selected to minimize
temperature expansion
coefficients and not melt.

[Robert Casey]

Tim Williams wrote:

>"Chuck Harris" > wrote in message
...
>
>
>>I am quite certain that this would break the pin seals, and
>>then the envelope.
>>
>>
>
>And then when the seals give, the vacuum sucks up LN and the whole tube
>is suddenly full of liquid ;)
>
>
>
Makes for a fluid soundstage..... :-)

[Chuck Harris]

WOOF!

-Chuck

TubeGarden wrote:
> Hi RATs!
>
> Yup. The pot may be cracked, but the chili is good :)
>
> Happy Ears!
> Al
>
>
> Alan J. Marcy
> Phoenix, AZ
>
> PWC/mystic/Earhead

[Ruud Broens]

"Robert Casey" > wrote in message
...
: Ken Gilbert wrote:
:
: >"west" > wrote in message
>...
: >
: >
: >>There seems to be a new craze on some glass NGs regarding sending your
tubes
: >>to be dipped in liquid nitrogen (absolute zero). The praises sung after
: >>having this procedure are not subjective, but an order of magnitude
positive
: >>improvement in just about all aspects of the sound. Some are sending out
: >>their entire collection of glass to be "dipped."
: >>
: >>
: >well, as one who has actually heard cryoed tubes, i can answer your
: >question honestly.
: >
: >YES i can hear a difference. a bit smoother, and less microphonic.
: >
: >
: >
: Anyone have an explanation as to why it should matter if the metal in
: the electrodes
: has one crystal structure vs another? Aside from the cathode, all that
: should do
: anything is the physical spacing of the cathode, grids and plate. As
: long as the grids and
: plate are made of conductive metal, the electrons shouldn't care if the
: grid is made
: of copper, iron or gold. The metal is likely selected to minimize
: temperature expansion
: coefficients and not melt.

That would be something for some experts in a metallurgy NG.

I guess if one would mount a tube in a socket and lower that upside down at
say 1 cm a minute into a thermos of liquid Nitrogen, the temperature
gradient would be quite sustainable for the glass envelope. No pin
dipping. Guess i read somewhere the total 'dip-time' used is 48 hours.
A 1 liter volume should last that time easily (well, unless you happen
to dip monsters like Svet EL509-II that is:).
What I can imagine is effects, being small, on the grid wires.
these will cool from the outside of the wire towards the core, which
could lead to a change in elasticity, possibly stiffening up the grid.
That could mean somewhat lower microphonics, but possibly
raised levels at higher frequencies.
just my 2 c,
Rudy
:

[Bob Weiss]

Tim Williams wrote:

> And then when the seals give, the vacuum sucks up LN and the whole tube
> is suddenly full of liquid ;)

Maybe for a millisecond or so. The LN2 hitting the room temperature
innards of the tube would flash boil instantly, releasing a large volume
of gaseous N2. This would cause a very high pressure inside the
envelope, which, if not released through the compromised pin seals,
would most likely result in the envelope rupturing violently.

Bob Weiss N2IXK

[Lord Valve]

Chuck Harris wrote:

> Hi LV,
>
> The biggest area of concern in a tubes construction is the seal
> between the glass and the metal pins. The metal is selected to
> have a coeficient of expansion that is as close as possible to
> that of the glass.
>
> The designers never invisioned that you would instantly allow
> a 389F degree temperature differential anywhere on the tube.
> (70F room temp to -319F LN temp)
>
> I am quite certain that this would break the pin seals, and
> then the envelope.

OK, that makes sense. So - three hours in the freezer, followed
by three hours packed in crushed dry ice, and then you lower the
tube glass-first into the LN, slowly. Ya think? I'm curious to see
if there is actually any audible difference, but I'm sure as hell
not gonna shell out a raft o' bux to have some dipped. And I
have an ulterior motive...if this treatment will actually "fix"
anything that's wrong with the tube, well...I have a few thousand
tubes that have **** wrong with 'em. ;-)

BTW, how about temperature treatment in the other direction?
I've heard of baking 'em in the oven, but how about something
more radical - lasers?

Lord Valve
Still Curious

[Fred Nachbaur]

Lord Valve wrote:
>
> Chuck Harris wrote:
>
>
>>Hi LV,
>>
>>The biggest area of concern in a tubes construction is the seal
>>between the glass and the metal pins. The metal is selected to
>>have a coeficient of expansion that is as close as possible to
>>that of the glass.
>>
>>The designers never invisioned that you would instantly allow
>>a 389F degree temperature differential anywhere on the tube.
>>(70F room temp to -319F LN temp)
>>
>>I am quite certain that this would break the pin seals, and
>>then the envelope.
>
>
> OK, that makes sense. So - three hours in the freezer, followed
> by three hours packed in crushed dry ice, and then you lower the
> tube glass-first into the LN, slowly. Ya think? I'm curious to see
> if there is actually any audible difference, but I'm sure as hell
> not gonna shell out a raft o' bux to have some dipped. And I
> have an ulterior motive...if this treatment will actually "fix"
> anything that's wrong with the tube, well...I have a few thousand
> tubes that have **** wrong with 'em. ;-)
>
> BTW, how about temperature treatment in the other direction?
> I've heard of baking 'em in the oven, but how about something
> more radical - lasers?

Well, it seems to me that a raw laser beam would only be useful for
making small holes in things. Maybe a good technique for adding more
holes in the plate for added ventilation [joke].

Come to think of it, I suppose you could use a laser to spot-weld loose
structures. (Aha, now I get it! You've got a ton of Chinese 12AX7's that
are coming apart at the seams!)

If the laser beam were made wider using a concave lens, the heating area
could be increased. But then you might as well just use focussed
conventional (visible or IR) light.

I've heard of guys with way too much time on their hands re-flashing
getters using a microwave. This one's definitely in the "YYMV"
department. But if you've got gassy tubes with worn-out getters, what's
to lose by trying?

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

[TubeGarden]

Hi RATs,

OK, so it clears the clogged cathode. I knew it did something good for sick
tubes. Any port in a storm.

Got a sick tube? Try overheating the filament for a few minutes. Fever isn't
such a new thing, fever started long time ago ;)

Microwave for getter flash, crackle, pop? Cool.

Er, Hot! Try if the high voltage trick doesn't help :)

Happy Ears!
Al

PS CV1673 and CV1732, 1960s replacements for 1920s HL2 and ML4, are doing Very
Well in my amp. I have added big oil can caps, 22.8uF 450Vdc, as bypasses to
the little cathode bias electrolytics, Panasonic 100uF 4V on HL2 and 220uF 10V
on ML4. Oh baby, oh baby. This is what living is all about :)


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

[Tim Williams]

"Fred Nachbaur" > wrote in message
...
> Well, it seems to me that a raw laser beam would only be useful for
> making small holes in things. Maybe a good technique for adding more
> holes in the plate for added ventilation [joke].

Too much of the laser would be absorbed by the glass. If even 1%, that's
a good couple of miliwatts concentrated in a small area.

> If the laser beam were made wider using a concave lens, the heating area
> could be increased. But then you might as well just use focussed
> conventional (visible or IR) light.

Or shove it in my furnace...

> I've heard of guys with way too much time on their hands re-flashing
> getters using a microwave. This one's definitely in the "YYMV"
> department. But if you've got gassy tubes with worn-out getters, what's
> to lose by trying?

Well, at worst, the microwave...

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

[Tim Williams]

"Fred Nachbaur" > wrote in message
...
> Hehe.. no problem. There's two of 'em for $5 each down at the Sally Ann
> right now. ;-)

Get 'em damnit! Just the scrap iron in those things is worth more than
$5, and that it's in the form of a transformer is icing on the cake! :)

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

[David Power]

On Thu, 31 Jul 2003 19:17:11 GMT, "west" > wrote:

>There seems to be a new craze on some glass NGs regarding sending your tubes
>to be dipped in liquid nitrogen (absolute zero). The praises sung after
>having this procedure are not subjective, but an order of magnitude positive
>improvement in just about all aspects of the sound. Some are sending out
>their entire collection of glass to be "dipped."
>I'm wondering if anyone here has heard of this and what is your opinion
>and/or experience?
>Cordially,
>west
>
>
If I remember correctly the tubes are put into a large insulated box
in racks. The liquid nitrogen is slowly dripped into the container at
a controlled rate not touching any of the contents into a cup at the
bottom of the box. It takes 24 hours to cool the whole thing down, the
contents are then held at the low temp for 24 hours and then a
controlled 24 hour warm up cycle is started.
Nasa has been cryo treating things for years.
I saw a small system a few years back and it didn't look all that
complicated.
I believe this is intended to release stresses in the metallic
structure and is supposed to have some effect on the crystal structure
of the metals as well. Some tubes do crack during the process.

David

[Richard]

As a research chemist who's been working with liquid nitrogen for ca. 40+
years now, I'd be very careful doing this with tubes. This procedure puts a
lot of stress on the glass-to-metal seals around the tube pins (i.e.
different coeffs. of thermal expansion can lead to stress-cracking). I sure
wouldn't put my Bugle Boy 12AX7's into liquid nitrogen (which is really not
absolute zero but about 77-degrees higher).

[David Power]

On Sun, 17 Aug 2003 16:49:15 GMT, "Richard"
> wrote:

>As a research chemist who's been working with liquid nitrogen for ca. 40+
>years now, I'd be very careful doing this with tubes. This procedure puts a
>lot of stress on the glass-to-metal seals around the tube pins (i.e.
>different coeffs. of thermal expansion can lead to stress-cracking). I sure
>wouldn't put my Bugle Boy 12AX7's into liquid nitrogen (which is really not
>absolute zero but about 77-degrees higher).
>
Its not really ever touching the liquid nitrogen, its just used to
cool the insulated vessel down. its done slowly enough that all the
components get a chance to adjust.