Cryogenically treated vacuum tubes...?

[Steve Conner]

They must have a piercing high end...

[Chuck H]

They must have a piercing high end...

Badum-bump-sst

[bob p]

Chuck, what happened to the dog butt???

[bob p]

Along the lines of Dai's post:

Cryogenically treating an entire tube after assembly makes no sense to me. Different materials within the tube are going to expand/contract at different rates when cooled and re-warmed. How can this possibly improve the geometry and alignment of the parts inside of the tubes?

If cryogenics made sense, we would see manufacturers treating individual components that go into the tubes cryogenically during the manufacture of those individual components, before the tube is assembled. Am I mistaken, or is that not what is being offered? My impression is that people are just freezing/thawing tubes after they've been assembled. Doing that makes no sense to me.

[g1]

Chuck, what happened to the dog butt???

I like the Heisenberg much better!
Especially after someone said the dog looked hungry and I won't mention the rest.

[Chuck H]

I guess I just got tired of being a dogs butt. I intend to get an actual picture of myself up someday. I just don't have any on my poot to upload right now since it's never been a priority. Heisenberg seemed like too obvious a choice, but no one else was using it so...

[salvarsan]

The legitimacy of cryogenic treatment of materials is well-established, as any Google Scholar search indicates.

Its value in audio is, of course, speculative, since many audiophiles, particularly those without a feel for science, get lost in self-justification when they go about gold-plating and polishing turds. They are your legal prey.

Cryogenic processing may have an effect on vacuum tubes if you reason that a more rigid metal structure is less susceptible to microphonics. The degree of improvement is probably minor since the structural integrity of electrode anchor (i.e., the mica wafer) is at the heart of things.

I have yet to find a scientific article that deals directly with conductivity changes in metal due to cryogenic processing, but I haven't looked especially hard.

[Chuck H]

No one said that cryogenic treatment of materials is bunk. Forgive my assumption but your opening sentence implies that cryogenics as a practice was in question. It is not. If you have read any of the material offered in your link you know that the benefits only apply to certain materials and indeed not all or even many. As I mentioned above, the filament is the only part in tube construction that is made of a material known to benefit from cryogenic treatment. I haven't had any trouble with filaments failing premature of other aspects of tube operation so I don't see any advantage to an improvement of the filament. And FWIW the actual degree of additional rigidity gained by even the most affected materials is very small. Further, and this is a good point if I do say so myself, why is a more rigid tube less microphonic!?! I should think the most malleable materials would be less prone to sustaining vibrations. And if cryogenics actually caused the internal structure of a tube to compact or contract, as has been suggested, wouldn't that be just as likely to loosen some tolerances as shrink others? Cryogenic treatment of materials is dandy. I've actually taken advantage of it for another avocation of mine which is why I know that there is no benefit to mild steel or mechanisms made from mild steel. So there can be no mechanical or electrical benefit from the treatment WRT tubes. With the possibility of any electrical benefit, even to austenitic steels still being purely speculative anyway. The goal of the cryogenically treated tube vendors is to marry a fairly inexpensive process that can be made to sound like it's beneficial to tubes in order to reap the profits of a specialized product without the need to actually provide one. It's a racket at this time and no proof of any benefit has ever been substantiated. These vendors make no attempt to rationally prove any benefit because if they did they wouldn't have a market.

[km6xz]

If a tube DID change, through cryogenic treatment it was bad to start with.

If it was truly a hard vacuum, the insolation of that void would prevent much impact except to the pins. With different material for pins versus rods extending through the glass, and the difference in Coefficient of expansion, the more significant change to expect would be premature failure of the glass<>rod seal and the pin<>rod swedged and soldered connection.
The most resistant item in our environment to cryogenic treatment would be a hard vacuum tube. Soft vacuum tubes might benefit but they are already bad.

More snake oil, and more cons....

Rather than describing how good it should be, a properly improved technology would measure the difference. If it can't be measured, how did they hone into the optimum design? I was hated at high end hi-fi shows for demanding proof in measurements, if they were not available, how could they tell when their design goal was reached?

Nothing to see here folks, move a long....

[Tom Phillips]

... Different materials within the tube are going to expand/contract at different rates when cooled and re-warmed...

Which beings up the concern that the glass to metal seal area where the pins go through the tube envelope could be stressed by the cryogenic treatment. Therefor, the net effect could be lower reliability after the magic treatment.

[R.G.]

The legitimacy of cryogenic treatment of materials is well-established, as any Google Scholar search indicates.

Heat treatment of materials is well established. Cryogenic treatment is a special case of heat treatment. However, the exact method of heat treatment makes a huge difference. It's the subject of huge amounts of inquiry. But if it's legitimate, it's measurable.

Its value in audio is, of course, speculative,

I think I'd state it another way: it's value in audio is pure BS without supporting measurements. Pretty much any time you see something saying "increased clarity and inner detail" or "air" about audio, it's a screaming klaxon alarm that the writer is trying to sucker you with stuff he can't prove and won't try to prove. It's prima facie evidence of intent to defraud. Worse yet, any request for proof of these claims will be met with an attack on the questioner as incapable of the subtle audio discrimination needed to detect things that instruments can't.

Cryogenic processing may have an effect on vacuum tubes if you reason that a more rigid metal structure is less susceptible to microphonics. The degree of improvement is probably minor since the structural integrity of electrode anchor (i.e., the mica wafer) is at the heart of things.

Things that are more rigid are almost inevitably less damped, so I suspect that it would make microphonics worse, albeit moving the susceptibilities to higher frequencies. But again, this isn't rocket surgery. Take a batch of tubes from one manufacturer, one production lot. Measure them for audio capabilities on a test jig rigged up to a shaker table and possibly inside a temperature cabinet. Take lots of data on all of them. Cryogenate half of them. Remeasure. Any difference at all? Do the statistics to show correlation with ANY change from as-received to cryogenically tortured. Publish the paper and/or go to the patent office if you find it.

Numbers are a HUGE sword over the head of the hucksters. That's why they avoid them.

I have yet to find a scientific article that deals directly with conductivity changes in metal due to cryogenic processing, but I haven't looked especially hard.

I'd be especially interested in a conductivity change that persisted after the metal was heat cycled by normal vacuum tube operations for several hundred cycles.

[Randall]

Which beings up the concern that the glass to metal seal area where the pins go through the tube envelope could be stressed by the cryogenic treatment. Therefor, the net effect could be lower reliability after the magic treatment.

This alone is enough to make me uninterested.

[Chuck H]

Let's take this to the next level. I'm not sure what the actual temperature of a tubes innards get to but I do know that to anneal any harden-able metal it's brought to a what's called "medium red" and held there for a time. "Medium red" isn't very specific but more accurate than you might imagine and IIRC it's around 1200F to 1300F. Lower temps (but still above tempering temps) will work too but it takes a lot longer. Since tubes operate at what I figure to be close to, but below "dull red" (1000F to 1100F), as I interpret by the fact that red plating is often a subtle bias adjustment away, and operate for long periods of time at this temperature I expect there must be degradation of any heat treatment. These are temperatures well above any rational tempering temperatures at the very least. And any effect of heat treatment, including those from cryogenic treatment, are undone by annealing metals. And again, non of this applies to tubes anyway because their not made with austenitic/martensitic metals. This is really the crux of the whole debacle. Tubes aren't made of stuff that permanently changes from cryogenic treatment.

[salvarsan]

Things that are more rigid are almost inevitably less damped, so I suspect that it would make microphonics worse, albeit moving the susceptibilities to higher frequencies. But again, this isn't rocket surgery.

Apparently it is. These resonances are generally described by modulus of elasticity and internal damping, more specifically described by viscoelasticity curves.

A plain example is the ringing in loudspeaker baskets made of cast metal versus pressed metal. I'm thinkina D and K series JBLs versus everything else.

Then you need to bolt them down. The basket ringing is coupled to and damped by the baffle, and the baffle has its own collection of internal losses that contribute the the damping.

I doubt that the plate rigidity/elasticity in a vacuum tube matters as much as a tight assembly in the mica wafer, i.e., when they get "bolted down." If the electrodes are a tight fit in the wafer, itself a layered structure that damps vibration, and the wafer is a tight fit in the bottle, it's a good bet that the assembly has lower microphonics. In other words, the coupling to the damped mount dominates all other vibration contributions.

Re: conductivity changes from cryogenic treatment
I was thinking of copper wire and magnet alloys. Callaham Guitars asserts that it imparts a small but significant change in their Strat & Tele pickups. What part of that is from copper and what part is from changes in Alnico crystal structure? Now that's the hard one to find research and numbers on.

[R.G.]

Apparently it is. These resonances are generally described by modulus of elasticity and internal damping, more specifically described by viscoelasticity curves.

Not really. Modulus and visco are not particularly rocket surgery, either. Yep, like ... um, noses, all materials gots them. The question du jour is what cryogenic treatment does to these magic properties, if any. And how much they change if it does change them, and how permanent the changes are.

A plain example is the ringing in loudspeaker baskets made of cast metal versus pressed metal. I'm thinkina D and K series JBLs versus everything else.

Then you need to bolt them down. The basket ringing is coupled to and damped by the baffle, and the baffle has its own collection of internal losses that contribute the the damping.

Aren't cast baskets a different metal than stamped baskets?

And yes, in very general generic generalities, resonances and susceptibility to microphonics ought to be changed by everything under the sun, at least a tiny little bit. However, the original presumption was
Cryogenic processing may have an effect on vacuum tubes if you reason that a more rigid metal structure is less susceptible to microphonics.
As yet, I don't see any way that a more rigid metal necessarily has better damping. It might be correct to say that cryogenic processing may have an effect on vacuum tubes if you reason that cryo processing affects the viscoelastic properties, but I'm thinking that more rigidity isn't helping.

I doubt that the plate rigidity/elasticity in a vacuum tube matters as much as a tight assembly in the mica wafer, i.e., when they get "bolted down." If the electrodes are a tight fit in the wafer, itself a layered structure that damps vibration, and the wafer is a tight fit in the bottle, it's a good bet that the assembly has lower microphonics. In other words, the coupling to the damped mount dominates all other vibration contributions.

So you're now opining that instead of:
Cryogenic processing may have an effect on vacuum tubes if you reason that a more rigid metal structure is less susceptible to microphonics.
it's more something like
"Regardless of the effect on the rigidity of the metal parts, cryogenic processing is unlikely to have an effect on vacuum tubes because the fit on the mica wafers dominates other effects."
Did I understand that correctly?

I was thinking of copper wire and magnet alloys.

Which parts of the insides of the tube did you think were copper wire and/or magnet alloys?

Callaham Guitars asserts that it imparts a small but significant change in their Strat & Tele pickups.

Does Callaham Guitars assert any research showing that's true? Any numbers on that?
The problem with that is that unless Callaham Guitars has some research behind it, I'd have to put their claims in the same bin as the claims from the folks that say that cryogenics makes tubes better - where are the numbers?

What part of that is from copper and what part is from changes in Alnico crystal structure? Now that's the hard one to find research and numbers on.

I'd sure be interested in reading any references to the effect on even combined copper and alnico structures.

There are a lot of references to cryo-treating metals for improved wear resistance. Sadly, the few places that talk about applications in audio seem to be offering a sop to the tweako dark side. Here's a few claims from one such place that will treat your audio whatevers:

Structural continuity.
?? Electrons can't get through wires already??


Reduction in compressed grains, more consistent grain size, less directional, less requirement for 'burn in'.
Consistent grain size and compressed grains make metals electrically directional and needing burned in? Snif, snif... anyone else smell snake oil?

Reduction in stress in the material, less susceptible to work hardening, longer service life with increased detail and transparency.
Yep, the reputable people do claim that there is an effect in especially tool steels of more internal hardening and wear resistance, for longer service life. It's just not clear that any audio going through the metals would have increased detail and transparency, or WHAT INCREASED DETAIL AND TRANSPARENCY EVEN MEAN.

Smoother surface for reduced skin effect for high frequency signals.
Skin effect is not an issue of the surface roughness. If it were, skin effect is not an issue for reasonable sized conductors at audio frequencies.

More regular distribution of grain size, overall increase in grain size hence less grain boundaries to interrupt signal flow.
More regular distribution of grain size *is* one of the niceties in steels. However, one of the things they strive for is smaller grain size. It's not clear that grain boundaries are an issue for conducting audio, whether the grains are larger or smaller.

Increased musical detail, clarity and transparency.
Kewl! More motherhood, apple pie, and chickens in every pot. It makes your audio more trustworthy, loyal, helpful, courteous, kind, brave, clean and reverent, too.

I suspect these guys know better. They just like to be friendly to the people who will hire them to cryo-treat vacuum tubes, speaker cables and CDs - yep, they mention cryo treating CDs on their site, like this will improve the digital readout of the CD's data.

Sigh.

WALOHCS