Bottlehead Forum
General Category => Technical topics => Topic started by: Doc B. on January 18, 2013, 06:31:26 AM
-
Tests done by Boeing/Sunstrand demonstrated cryogenic processing extended the life of circuit boards in military applications, specifically boards used in cruise missiles. Tests done by Honeywell on experimental thin film magnetic memory wafers showed increased conductivity of metallic layers, reduced residual stress between layers, and possible (but not fully confirmed) "healing" of vacancies in the layers. Tests on transformers showed treated transformers had significantly less hysterisis. The magnetic core saturated less. Tests on transistors showed a decrease in rise time. Other tests indicate greatly increased contact life on relays, switches, and circuit breakers.
I found this quote on a thread on the gearpage having to do with cryo treated guitar pickups. Don't know the original source
-
It might be cool to dip a pair of OPT and A/B the sonic results. Thanks for posting this Dan :)
-
We have compared, many years ago. What I recall was that the cryo'd trans sounded a little more smooth and "broken in".
-
My recollection is that the difference was incredibly tiny. These were Magnequest B7-5K preamp output transformers, with low-nickel cores. I still have the test box, it was a parafeed amp with switchable amounts of plate choke inductance. A 10% increase in inductance was much more clearly audible than the difference between the OPTs. Thing had Infinicaps at the output - those were hot stuff back then. (I just pulled it out to check.)
At around that time, everyone who tried agreed that de-magnetizing your tubes was seriously worthwhile. Haven't heard much about that recently. Of course, we were also de-gaussing our CDs and painting the edges green back then.
-
I am still very resistant to such 'tweaks'. Mind you, I come from the camp of 'wire is wire'. I have learned more since, but the 'quantum' stuff etc. is still snake oil to me.
-
Hmm, All this time I've been painting the whole CD green...John
-
I havent done that, but I do have MANY boutique fuses. So there.
-
Huh - I wonder if the extended circuit board life could be attributed to reducing tin whiskers?
http://nepp.nasa.gov/whisker/background/index.htm (http://nepp.nasa.gov/whisker/background/index.htm)
-
. . . At around that time, everyone who tried agreed that de-magnetizing your tubes was seriously worthwhile. . . . Of course, we were also de-gaussing our CDs and painting the edges green back then.
Now I have a use for that old bulk tape demagnetizer I have.
-
Now I have a use for that old bulk tape demagnetizer I have.
Hah! I still have one of those!
-
How exactly does one increase the life of a cruise missile? I mean... it goes boom. Not much life beyond that. :o
Cryo treatments have the potential to induce phase changes/precipitation or recrystallization in materials, particularly if they are under a lot of stress (as thin films tend to be, depending on the method of manufacture). Such changes then will typically result in a reduction of said residual stress. Larger bulk materials would likely benefit more from a heat treatment and more careful manufacturing methods than a cryo "fix".
-
What hasn't been cryoed? I saw an experiment with expensive blades for hand planes that had undergone this treatment. Much to the praise of the hand plane company that did the experiments, they said that there was no significant advantage for this treatment. Yah blades and tubes and wire are all different, so I am open to anything that might improve performance for a particular part. It's just that so often, in such discoveries, it is sold as the 'answer'. They call it marketing. On the other hand, there quite a few things that are worthwhile to try. Maybe that is our job.
-
You can order your favorite razor cartridges cryo'ed. They are expensive (more than usual ) , but I have heard good reviews.
-
Very interesting post.
As a dentist, I daily employ various heat and cold treatments in the lab to change the grain structure of various metals (usually gold, copper platinum and palladium) in order to alter their physical and working properties. The changes in the microscopic grain structure after cryogenic or heat treatment is clearly evident under a scanning electron microscope and is taught in all metallurgical engineering curriculums. It has in fact been used for thousands of years dating back to the metal artisans in ancient china.
Denis Boyle the electrical engineer who owns Chimera Labs, advocates and sells cryogenically treated OCCC wire in all his litz braided wire and cables. http://www.chimeralabs.com I have a bunch of his raw wire here and have used it for numerous DIY cables and internal wiring. Dennis is one of the most knowledgeable Valve SET guys I have had contact so I am confidant that there is really something to it. Unfortunately, for me Litz braiding over 3 strands as a bitch for me!
http://www.chimeralabs.com/faq.html
-
cryo treatment does tug on me now and then. I want to ask what happens to a tube that was first cryoed, changing the grain structure of it's metal parts. Then when heated to operating temps, does that undo the 'goodness' of cryo treatment in the first place? Kind of like taking the temper out of a blade. All in all, I think that there is much that we don't know, but that doesn't mean it is suspect.
-
I don't think it is black magic. Treating metal with temperature changes is a time honored tradition. I worked for Alcoa. I got some information from one of our process engineers. Heat treating metal has a lot of fine points. How quickly a metal passes through a phase boarder is important to the properties that are being imparted.
That is the best an EE can explain this stuff. Sorry!
-
We were visiting the Physics department the other day for a scholarship presentation for my son, and I did notice the huge cryo tanks outside. I was kind of wishing I had some of my wires with me!
-
We were visiting the Physics department the other day for a scholarship presentation for my son, and I did notice the huge cryo tanks outside. I was kind of wishing I had some of my wires with me!
...or th neighbors cat
-
Had a physics class in the late 70's, in which the prof did the notorious rose dipped in liquid nitrogen then shatter it on the lab bench demo. He then proceeded to quickly dip his finger in and out of the stuff, and commented, "interesting, it freezes the outer layer of your skin."
Yeah, a professor e-fuckin-meritus of the UC Berkeley Physics Dept. apparently didn't grok that his skin would freeze in liquid nitrogen even after he dipped another organic life form in it and proceeded to vaporize it with a flick off his wrist. No, I don't how how he survived long enough to become emeritus. From today's perspective it was sort of a longhair version of "hold mah beer - watch this!" Bubbameritus? Darwin must have watching over him that day. I had a daymare of him leaving his finger in the dewar for a couple seconds and whacking his finger on the lab bench and busting it off for some time after that.
-
I think I saw something like that on TV recently. I remember that the reason the skin didnt immediately freeze was because of a layer of frozen H2O or air that protected the skin for short time that it was submerged.
-
Dan, Berkeley, Hmm, kind of explains some of his quirks. Was this in the 60s? By the way, I have an uncle, Calvin, called Bubba. He and Francis are the last of my mother's generation in the Allen family.
He is more of a "hold my 20 year old scotch and watch this kind of guy." We shot off a lot of fireworks at his house.
-
cryo treatment does tug on me now and then. I want to ask what happens to a tube that was first cryoed, changing the grain structure of it's metal parts. Then when heated to operating temps, does that undo the 'goodness' of cryo treatment in the first place? Kind of like taking the temper out of a blade. All in all, I think that there is much that we don't know, but that doesn't mean it is suspect.
Using steel as an example... iron has a particular phase/crystal structure (atomic arrangement) at room temperature. If you raise it above a certain point, it will actually change structure, with some minor accompanying changes in properties. If you lower the temperature back slowly, it will revert. If you do it quickly (such as with quenching), you will "freeze" the structure in place before it can change back. The quench creates a lot of internal stresses (because this second phase does not normally exist at room temperature) and the formation of little carbides. Both of these lead to large increase in hardness, but also brittleness.
Tempering is reheating at a much lower point (well below the point where it changes phase), to remove some of the internal stresses and maybe change the shape of the carbides. Internal stresses are relieved by recrystallization (new grains) and/or grain growth, both of which literally eat up the highly stresses regions of the metal (predominantly in the grain boundaries and in lattice imperfections).
To understand part of how cryo works you need to understand how phase changes occur, which is easier with heating. When materials change phase, you are essentially moving them from one (relatively stable) energy state to another. However, to move from one state to another requires getting over a high energy wall/fence in simplistic terms. You have to push it over before it can fall back down and stabilize on the other side. So this is in heat treating where you heat something up to bring up its energy level and push it over a wall, then quench or do some other trickery to get it to stay on that side of the wall when you're done.
Internal stresses muck with things and add to the energy state of your material, meaning (but not always) that you need to put in less energy to reach over the wall. Also, moving over the wall in this case can permanently remove those residual stresses, so they don't come back later (sometimes). Thick of it like a shoddy step ladder that breaks as soon as you get over the fence
Cryo treatments... if I'm keeping to this analogy... a blizzard just rolled in and dumped 6 feet of snow, and the plows just built a mountain on your yard. What fence? The kids can sled down the hill like nothing's there. Ok I'm exaggerating. So uh where was I? You have a potential reduction in residual stress, recrystallization, and phase changes.
So coming back to the question of "undoing" the cryo treatment of a tube... well, uh, yes and no. Heating makes changes regardless. The cryo just changes (maybe) your starting point.
I think I saw something like that on TV recently. I remember that the reason the skin didnt immediately freeze was because of a layer of frozen H2O or air that protected the skin for short time that it was submerged.
The heat emanating from your hand will literally boil off the liquid nitrogen before it can reach your hand... For a very short time. It basically just creates a protective gas layer. Don't try this if you're a particularly hairy guy though, as the hairs will wick the liquid more quickly to your skin.
The inverse can also be done by dipping your fingers/hot dogs into molten metal. Moisture/airbubble will protect your fleshy dangly bits for a very brief moment, although the weight of the molten metal will make it push in much quicker than liquid. In any event, don't try that one at home and just watch the mythbusters episode.
edit: typos and clarification
-
Thank you for helping me understand this set of physics. I wonder these questions with no scientific evidence, and only presume of what might occur or not. Then, usually a marketing trick is ready to claim more than the evidence holds, causing the buyer to believe.
-
Armaegis,
Yeah, what you said. The key to what happens is the speed at which the metal goes through the temperature changes. I can only guess that a Cryo service know this and make the changes accordingly.
-
A cryo treatment won't necessarily make any changes to a material. However, if it does it will most likely take it to a lower (more stable) energy state afterwards. Whether or not this will have a positive effect on whatever electrical jimjam you're measuring is up to the marketing guys.
Reduced residual stress is usually a good thing, unless you're using that residual stress to increase the strength of the material. How residual stress affects electrical properties... I have notions, but not enough to speak firmly on the matter.
Precipitated phases and recrystallization will decrease average grain size and increase grain boundary percentage and increase material hardness. Grain growth will do the opposite (up to a point). Both of these can occur simultaneously. Again, how this affects electronic/sonic flimflams is left to somebody else.
-
I do a lot of rebuilds on Fisher, Scott, McIntosh, and the other 7591 based amps. JJ are a disaster. The Electro Harmonix we had used as both cryo and non treated. There is a difference, a big one, and cryo is the only tube we buy now and for the last 8 years.
With cryo, The bass is deeper with far less distortion, highs are cleaner and detail is better, subtle clues emerge, better sound stage. The best part is the tubes last far longer. I can run 8 hours a day on the cryo for about 3 years before one or more begin to fade or act up. With the non cryo treated 12 to 18 months, and most of the quad is done. The cyroset tubes always have at least two tubes testing out at 80 to 90% when a check up is due. Recently I check a quad that has lasted 3 years, the set had one tube testing under 85% and the other 3 were over 90% in both emission and gm as well as plate current matching. That is hard to beat. They run circles around vintage.
-
I just remembered what my first system was - sorry, having a flashback from another thread - Bud reminded me. It was a Fisher.
-
You have to be careful about claims about cryo treatment of electronic materials. While there are many instances where it has marvelous effects - that is primarily with a material that undergoes phase changes at low temperatures (classic example is steel). Cryo treatment is great for certain engine parts, tools or blades - primarily due to the Martensitic transition that steel goes through at low temps (although the effect can be problematic as well - look up the Liberty ships in the North Atlantic during WWII - there are other examples in history also).
Many of the materials that cryo is applied to for audio do not have any of these phase changes - most notably copper (a nice, simple Face-Centered Cubic structure).
In the absence of a phase change, then simple kinetics apply - and the effects usually involve things like grain structure changes or removal of crystalline imperfections like dislocations and the like (for now, lets ignore diffusion of impurities). Most of these things are strongly temperature dependent, where an increase in temperature causes things to happen (and a decrease in temperature has the inverse effect - a drastic slowing of the change). Here, cryo is not going to cause any changes.
For most materials used in vacuum tubes (or interconnects), it is hard to come up with an explanation of why any change might happen based on materials science principles.
My humble opinion...
Rich
-
Rich,
Thank you for the reply. I still find this fascinating. And while some materials respond as opposed to others, it keeps me pondering. Good point ade earlier about the rate of temp change, coming AND going.