sales@effectrode.com

  • About Us
  • Knowledge Base
    • Tubes
    • Pedals
    • Science of Tone
    • Binson Echorec
    • History
    • Quality
  • News
  • Press
  • FAQ
  • Vacancies
  • My Account
  • Login
logo
  • Store
  • Stockists
  • Artists
  • Contact
  • | Newsletter
  • Store
    • Accessories
    • Pedals
    • Vacuum Tubes
  • Knowledge Base
  • Stockists
  • Artists
  • Contact
  • FAQ
  • About
  • News
  • Press
  • Newsletter
  • 0

    Shopping cart

    0
    Cart is Empty

Cryogenic Treatment of Tubes: An Engineer’s Perspective

  1. HomeKnowledge BaseCryogenic Treatment of Tubes: An Engineer’s Perspective

Cryogenic Treatment of Tubes: An Engineer’s Perspective

by Phil Taylor

As an electronics engineer, and someone who works in the highly improbable trade of making vacuum tube “effectification” for electric guitar, I’ve more than a passing interest in anything that might help improve the sound quality, and reliability of these glowing, glass critters because they’re very tricky to work with! There’s variability in microphony to consider, and electrical self-noise—even between tubes from the same factory batch—and I’ve often asked myself if there might be some kind of a fix for this. It seems a shame to bin a completely functional vintage tube, just because it generates slightly more hiss than expected, or is a little more sensitive to picking up external vibration than another. I’d heard claims about how “cryogenic treatment” (a.k.a. cryo-treatment) can improve the tone of tubes; claims like it, “causes metallurgical molecular changes in the metals within the tube which enhance tone and increase overall life”. Does enhancing tone mean lowering noise and microphony? And can cryo-treatment really improve a tube’s reliability? Could cryo-treatment be the silver bullet I’d been searching looking for? Being naturally curious, and concerned about the steadily growing pile of below par tubes that was cluttering up the workshop, I had to explore this further…

What is Cryogenic Treatment?

broken_gear_tooth
Cryogenic treatment is used to improve the durability of moving steel parts.

Cryogenic treatment is a process of cooling steel alloy down to very low temperatures (−190 °C) to increase its surface hardness to improve its resistance to wear, the practical application being to extend the life of cutting tools, gear teeth, moving engine parts, that kind of thing. These super-cooled temperatures alter the crystal structure of steel by completing the conversion of austenite to martensite making it harder. Now, I recall making a screwdriver in metalwork class at secondary school many years ago. The tip of the screwdriver was hardened by heating it up with a blowtorch and then cooling it rapidly (‘quenching’) by plunging it into a bucket of water. It’s my understanding that quenching the steel in this way and not allowing it to cool down slowly prevents austenite from forming and makes the steel much harder and more brittle. The process isn’t 100% perfect though as steel still contains some austenite crystals. Apparently cryogenic treatment completes the conversion to further harden it.

Effect on Vacuum Tubes?

So cryogenic treatment can work to improve the hardness of ferrous metals such as steel, but what about a vacuum tube—a tube is not a lump of steel—like a wristwatch, it’s a delicate and complex mechanism composed of many different parts, which in turn are made from different types of materials. The metal electrodes are mainly high purity nickel for the plates and heater cover (cathode), tungsten alloy for the heater wire, molybdenum for the grid wire, copper support posts and the heater is coated with a mixture of strontium/barium oxides. All these tiny metal parts are supported by thin mica discs within a glass envelope.

Austenite and martensite crystal lattices
Two different crystal lattice structures that occur in steel which have absolutely no measurable effect on tone.

Cryogenic treatment of materials other than steel is a specialised subject and published literature on the subject is sparse. This means we can only speculate as to what effect chilling a tube down to utlracold temperatures will have on the non-ferrous materials that make up its many, intricate internal parts. I did, however, come across research papers describing how cryogenic treatment hardens aluminium though; perhaps it’s possible that the process will also harden copper, nickel and the other metals utilised in the construction of tubes too? There are no moving parts within a tube, and hence no mechanical wear, but hardening the metal electrodes could in principle make them stiffer, and stiff electrodes are good thing in tube. Any minuscule displacement or bending of the grid, plate and cathode relative to one another results sensitivity to vibration pickup—stiff, and accurately machined electrodes limit this movement keeping microphony to a minimum. But it should be kept in mind that cryogenic treatment is ordinarily employed to complete the conversion of austenite to martensite in hardened steel as described earlier; the metal electrodes, and other parts inside a tube aren’t quenched to make them super hard to begin with, which means there is no conversion to complete. So, if cryo-treatment doesn’t affect the hardness or stiffness of the electrodes then what benefits does it impart on a vacuum tube?

Tube on ice
Taking a tube down to extreme low temperatures runs the risk of ruining tube permanently and irreversibly unless precautions are taken to protect it from the stresses of the procedure. [photo courtesy of 'TheTubeStore.com']

Well, it could be argued that cryo-treatment doesn’t benefit tubes at all, in fact does quite the opposite. The severe cooling process, if anything, degrades the performance of these thermionic devices. Here’s why. Subjecting a tube to a frosty and unforgiving −190 °C will result in differential rates of thermal contraction of the various materials within the tube. There are no ifs, ands, or buts about this, it’s basic physics. As the temperature plummets the metal pins on the base of the tube radially contract; they shrink and pull away from the surrounding glass putting incredible stress on the glass-to-metal seals. Technically this known as tensile stress; the forces are colossal—measured in 100,000s Kg/cm² [see the chapter on “Glass-To-Metal Sealing” in Materials and Techniques for Electron Tubes (1960) by Walter H. Kohl]. Ultimately this can lead to a breach, allowing air to enter the glass envelope and compromise the vacuum; this typically results in excessive noise, shortens tube life and can even kill the tube outright.

And the same physical principles apply to the “cage“. Differing rates of thermal contraction of the mica spacers and metal electrodes within the cage assembly can cause movement, potentially loosening the electrodes resulting in adverse microphony. Given this, it should come as no surprise that:

Tube manufacturers never designed or intended tubes to be stored at cryogenic temperatures.

It’s not recommended practice to mishandle electronic components in this way. It’s worth noting that electronics component manufacturers publish datasheets that specify temperature ranges for storing and operating their devices—none recommend storing their components at temperatures colder than a midwinter’s night on Mars. In fact, thinking about, it NASA install heaters on their Mars rovers, and deep space hardware, to prevent batteries and onboard electronics being damaged by the extreme cold—NASA’s engineers are well aware of the risks involved when subjecting electronic components to abnormally low temperatures.

This is even more true for vacuum tubes, which are especially delicate components. Ironically, cryo-treatment is liable to ruin a tube permanently and irreversibly unless precautions are taken to protect it from the stresses of the procedure. The temperature must be cycled (decreased and increased) slowly for the reasons outlined above and the humidity has to be maintained at near zero to prevent condensation forming and oxidising exposed metal parts. Additionally, the utmost care needs be taken when handling a tube whilst it is at cryogenic temperatures as the physical properties of the materials from which the tube is constructed alter.

At at around −200 °C many materials become fantastically fragile and prone to fracture or shattering, meaning cryo-treatment increases the odds of loosening something within the electrode assembly or worse still, embrittlement and fracturing of precisely engineered and delicate internal parts. There’s a dramatic scene in the “Terminator 2″ movie where a single bullet fired by Arnold Schwarzenegger shatters the frozen T-1000 terminator into a thousand pieces, however take a look at this short video of a platinum cup being submerged in liquid nitrogen for a real experimental demonstration of how embrittlement drastically alters the properties of metals.

Effect on Tone?

I could find no scientific literature relating to the effect of cryogenics on tone. There are no research papers, text books or technical data published by any tube manufacturer at any time that even mentions cryogenics, let alone advocating the process as a method to alter the physical properties of a vacuum tube. So just how does it work? Does cryo-treatment affect now electrons are emitted from the cathode? Does it somehow change the way electromagnetic fields form within the tube? Does it improve the bonding of the oxide coatings to the cathode or remove residual contaminants to make the tube electrically quieter? Does cryogenic treatment affect the tube in any measurable or audible way at all? There are many questions, but no answers; how it works is… unknown. Even the handful of vendors enthusiastically pushing cryo-treatment don’t seem to know either.

Sure, they make “claims”, but claims are not a scientific explanation. Vendors discuss in great detail about how they cryogenically treat tubes, but provide no proof to support why it improves their tone. Instead their websites are littered with blurb about how their cryo-treated tubes possess “tighter focus from top to bottom”, “more holographic 3-D sound-stage”, “more subtle inner resolution extracted from recordings”, “tighter bass”, “increased dynamic range”, “faster transient response” and even references to NASA’s research and great scientists such as Albert Einstein.

G.A. Briggs A To Z In Audio
There are no audio text books that even mention cryo-treatment, let alone advocating it as procedure to improve the tone of tubes—ask G.A. Briggs.

This all sounds very impressive, but cuts no ice in science—if this extreme freezing process really does have an effect on tone then where’s the evidence? It’s not unreasonable to expect claims be supported by measurements and data; independently assessed noise and microphony tests would be a good starting point, preferably accredited by an external body such as the National Physical Laboratory. But vendors provide no hard evidence, only fluffy opinions.

Girly scientist holding test tube
“Better Tone Through Cryogenics”, eh? Has anyone put that to the test?

At this point it would be easy to write-off cryo-treatment as “snake oil“, hogwash, a fake or a scam or, at best, a placebo. But let’s just go back a step: if cryo-treatment is actually damaging tubes as speculated earlier on, then might this reasonably explain it’s apparent effectiveness? Could it be that subjecting tubes to the stresses of extreme cold provides a test methodology reveal potential early failures—a kind if negative null test? That is, the cryogenic process doesn’t improve performance, it’s simply that people are listening to hand-selected tubes because all the weak tubes would have been weeded out. Could this be the reason why some people can hear a difference?

On the face of it this might seem like a plus for cryogenic treatment, but bear in mind that fierce freezing puts unnecessary stress on the tube; stresses that can impair, or even damage it. The process of cryogenic cooling introduces additional uncertainties into the manufacturing process, which will almost certainly shorten a vacuum tube’s life expectancy—technically, the MTBF (Mean Time Before Failure) is reduced. By how much is impossible to say, as there are no published life test data comparing cryogenically treated and stock tubes.

The truth is out there… and a good engineer, or scientist, would want to know the truth—more than that, they’d need to know. It’s how they are—they have inquisitive minds. Like Einstein they’d feel compelled to understand the physics, or they’d never get to sleep at night. Even then, they wouldn’t get any sleep because they’d be conducting experiments late into the night; taking measurements, taking amphetamines, drinking copious amounts of strong, black coffee; they’d collect, tabulate, plot and analyse the data; they’d check and re-check experimental procedures, weigh the evidence and write up their findings. Finally, they’d submit their thesis for intense scrutiny by other boffins in the field, a ritual formally known as “peer review”. If all goes well, and they manage to survive the ravages of the peer review process, then, and only then, would it be reasonable for them to claim that “Better Tone Through Cryogenics” is fact and not just fiction. This is the way great advances in science, and guitar tone, are made. Sounds laborious, and it is—scientific discovery is a glacially slow process but it gets there in the end, eventually.

Table of results for cryo-treatment test data
Vital statistics for six JJ ECC83 tubes. One of these tubes has been cryo-treated—can you guess which one?

So, in the absence of any hard data from tube vendors Effectrode undertook our own comparative tests of cryo-treated JJ ECC83 and ECC81 tubes. We tested them against untreated reference tubes on an “AVO” MKIII Valve Characteristic Meter and later performed audio listening tests using a Fender ‘Deluxe Reverb’ guitar amp (the tubes were substituted into the input and phase splitter stages in the amp’s circuitry). The results? Well, we were unable to measure any significant differences in self-noise (demonstrated in the short video below), gain (see the  table above) or emission. Further, “blind” A/B audio tests revealed no tonal differences or improvements between the treated and untreated tubes. The amp didn’t sound more “holographic” or ” possess more subtle inner resolution”; and, unsurprisingly, it wasn’t any quieter either. This result was not unexpected.

Didn’t Mullard Know About It?

And it’s worth considering this: if there is any merit in the cryogenic treatment of tubes then surely manufacturing giants Mullard-Philips or Sylvania would have made use of the process. They were in the business of making tubes, not just for guitar and hi-fi amplifiers, but for mission critical military, aerospace and scientific instrumentation applications. They were highly motivated to improve their production processes. They had vast pool of scientific and engineering resources at their disposal. Mullard’s 43 acre site at Blackburn, Lancashire, Great Britain was one of, if not the, most advanced tube manufacturing facility in the world, and it even possessed it’s own liquid oxygen and liquid hydrogen production plant.

mullard_blackburn_oxygen_and_hydrogen_plant
Oxygen and hydrogen production plant on the Blackburn site – Mullard had the motivation and resources to explore cryogenics.

The site employed almost 7000 people amongst which were all kinds of specialists including physicists, chemists and metallurgists, resources far beyond the small handful of eastern tube factories that serve the guitar industry today. If there had been anything in cryo-treatment then surely Mullard must have known about it. Perhaps they did; perhaps somewhere, buried in some university basement, library or an old radio ham’s attic, is a technical paper written by a Mullard engineer in the early 1960s titled ‘An Investigation into the Effect of Cryogenic Temperatures on Thermionic Emission’. I’ll leave it to the reader to speculate how long the odds are of that paper ever seeing the light of day are, and, if it did ever show up, would it put the big freeze on the tube cryo-treatment industry?

How to Avoid Tube Marketing Hype 101!

Retro salesman
The power of marketing hype is the power to sell pretty much anything to anyone.

The vacuum tube industry today certainly does seem to suffer from more than its fair share of marketing hype. Like the washing-up powder market, the tube market is awash with all sorts of flimflam; and cryo-treatment is just the tip of the iceberg. There are other pointless audiophile accessories, such as tube dampers, tube coolers and that old-time favourite, tube rebranding is still going strong, even today—you can still buy a new ‘Mullard’ ECC83 tube, even though Mullard ceased to exist as an entity during the last part of the 20th century. These guys cannot be serious, can they? Do they really expect us to believe these cheap gimmicks and cheap-ass marketeering nonsense are a substitute for real innovation? Please knock it off guys—it’s really, really annoying.

So, my advice when buying tubes is simply this: invest in tubes from a reputable vendor that checks and matches them on a tube tester and guarantees them. Or, better still, seek out vintage vacuum tubes made by the likes of Mullard, Sylvania or the other giants from the golden age of tube manufacturing—genuine N.O.S. tubes can still be found and there are even a few good deals to be had.

On a final note, the best means of avoiding being duped by marketing hype is to educate yourself. I can highly recommend taking a look at Materials and Techniques for Electron Tubes (1960) by Walter H. Kohl the Senior Engineering Specialist of Special Tube Operations at Sylvania and Electron Tube Design by RCA (1962). You’ll find nothing about cryo-treatment in these texts only information relating to the construction methods and quality of materials, that is, the stuff that’s genuinely relevant in the design of a good quality tube, and, these texts also provide a fascinating, nostalgic glimpse into the world of the 1960s, a time when manufacturers went to unprecedented lengths to design and construct tubes that were as near perfect as possible. After an hour or so’s reading from either book you’ll be in the know, a bona fide tube guru knowing what’s important in tube design and, what’s not so important.

In Conclusion

Anyway, that’s my two cents worth on tube cryo-treatment. To summarise, there is variation in the construction of vacuum tubes and these variations have a direct effect on a tube’s tonal characteristics. They’re due to engineering limitations, or to put it another way, the tube manufacturers’ ability to fabricate these complex thermionic devices consistently and accurately. Mullard (and Sylvania), in their heyday, with their large-scale research and manufacturing facilities and a wealth of expertise, got as close as anyone ever could to building the perfect tube. However, despite this they were unable to attain the level of precision required to ensure their tubes possessed uniformly low microhpony and self-noise. Over the decades Mullard made numerous changes to the construction and materials used in their tubes in an effort to iron out these problems, but they never considered deep freezing them; why would they?—there was nothing to indicate it would work.

It would be magical if simply putting tubes in the freezer was a ‘silver bullet’ that could reduce inter-electrode movement and kill microphony; improve the insulation properties of mica spacers to prevent noisy current leakage paths; and somehow restore, revitalise and smooth out fluctuations in electron emission from the cathode oxide coating and make the tube as good as new. But I cannot begin to imagine how this “cure-all” works—’magical’ really is the right word to use here—because cryogenic treatment of tubes is not science. There are no solid scientific explanations describing how the process might affect the electrical or mechanical characteristics of a tube in any beneficial way. Nor are there even the most sparse comparative test results to validate claims for improved sonic performance—by the way, ‘V2’ was the cryo-treated tube in the table of tests shown earlier on.

The bottom line is that cryo-treatment is no remedy for inferior materials, manufacturing defects or deterioration caused by ageing, and, it won’t transform a cheap rebranded modern manufacture tube into a genuine vintage Mullard tube either—it just doesn’t work that way. And, those cryo-treated tubes we tested came highly priced. Not a great financial investment, but perhaps an investment in knowledge; because we’ve learned cryo-treatment has about as much influence on the tone of a tube as the positions of the stars and planets above—and I’ll put my money on science, rather than astrology, every time. As for my heap of dodgy old tubes, well, I’ll just have to put them back on ice…

If you’re interested in what the Mullard Blackburn factory was like in its glory days then do take a look at the following article ‘Speed, Efficiency & Perfection – Aims That Have Built a Mammoth Factory in 16 Years’ originally published in 1954 in the ‘Blackburn Times’ not long after the factory opened.

In This Section

  • Black Plate Tubes
  • Chemical Highlights of Tube Manufacturing
  • Cryogenic Treatment of Tubes: An Engineer’s Perspective
  • Developments in Trustworthy-Valve Techniques
  • Evolution of the Tube
  • Foil Those Tube Forgers
  • Microphonics
  • Mullard ECC83 (12AX7) Reissue vs Original – A Physical Comparison
  • Mullard ECC83 (12AX7) Reissue vs Original – An Electrical Comparison
  • Noise
  • Oxide Cathode Life: Investigations into the Causes of Loss of Emission
  • Signal Tubes
  • Speed, Efficiency & Perfection – Aims That Have Built a Mammoth Factory in 16 Years
  • Subminiature Tubes: The Future of Audio!
  • That’s a Sylvania tube, the print is green, no, it’s blue
  • The ‘Magic Eye’
  • The ’12AT7′ Tube
  • The ’12AU7′ Tube
  • The ’12AX7′ Tube
  • The 12AX7 Tube – The Cornerstone Of Guitar Tone
  • The 6SN7GT – the best general-purpose dual triode?
  • The Accurate BSPICE Tube Models
  • The Cool Sound of Tubes
  • The Inner Workings of Vacuum Tube Buffers
  • The Tube Family Tree – Part 1
  • The Tube Family Tree – Part 2
  • The Tube Family Tree – Part 3
  • Tube Vendors
  • Tubes: The Old Verses the New
  • Vacuum Tubes and Transistors Compared
  • Valve Microphony Part 1: Production of Microphony and Methods of Investigation
logo
+44 (0) 1782 372210 sales@effectrode.com
facebook instagram twitter pinterest rss soundcloud
Newsletter

Useful Links

  • Shipping Policy
  • Refund Policy
  • WEEE Policy
  • Privacy Policy
  • Warranty Policy
  • Register Your Pedal

Instagram

Copyright © 1963-2022 EFFECTRODE THERMIONIC. All Rights Reserved.
We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept All”, you consent to the use of ALL the cookies. However, you may visit "Cookie Settings" to provide a controlled consent.
Cookie SettingsAccept All
Manage consent

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. These cookies ensure basic functionalities and security features of the website, anonymously.
CookieDurationDescription
_GRECAPTCHA5 months 27 daysThis cookie is set by Google. In addition to certain standard Google cookies, reCAPTCHA sets a necessary cookie (_GRECAPTCHA) when executed for the purpose of providing its risk analysis.
cookielawinfo-checkbox-advertisement1 yearSet by the GDPR Cookie Consent plugin, this cookie is used to record the user consent for the cookies in the "Advertisement" category .
cookielawinfo-checkbox-analytics11 monthsThis cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Analytics".
cookielawinfo-checkbox-functional11 monthsThe cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional".
cookielawinfo-checkbox-necessary11 monthsThis cookie is set by GDPR Cookie Consent plugin. The cookies is used to store the user consent for the cookies in the category "Necessary".
cookielawinfo-checkbox-others11 monthsThis cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Other.
cookielawinfo-checkbox-performance11 monthsThis cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category "Performance".
JSESSIONIDCookie used to allow the Worldpay payment gateway on the website to function.
machineCookie used to allow the Worldpay payment gateway on the website to function.
viewed_cookie_policy11 monthsThe cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. It does not store any personal data.
wordpress_logged_in_Users are those people who have registered an account with the WordPress site. On login, WordPress uses the wordpress_[hash] cookie to store your authentication details. Its use is limited to the Administration Screen area, /wp-admin/ After login, WordPress sets the wordpress_logged_in_[hash] cookie, which indicates when you’re logged in, and who you are, for most interface use. WordPress also sets a few wp-settings-{time}-[UID] cookies. The number on the end is your individual user ID from the users database table. This is used to customize your view of admin interface, and possibly also the main site interface.
wordpress_sec_1 yearProvide protection against hackers, store account details.
wordpress_test_cookieTest to see if cookies are enabled.
wp-settings-1 yearWordPress also sets a few wp-settings-{time}-[UID] cookies. The number on the end is your individual user ID from the users database table. This is used to customize your view of admin interface, and possibly also the main site interface.
Functional
Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features.
Performance
Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors.
CookieDurationDescription
_gat1 minuteThis cookie is installed by Google Universal Analytics to restrain request rate and thus limit the collection of data on high traffic sites.
Analytics
Analytical cookies are used to understand how visitors interact with the website. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc.
CookieDurationDescription
_ga2 yearsThe _ga cookie, installed by Google Analytics, calculates visitor, session and campaign data and also keeps track of site usage for the site's analytics report. The cookie stores information anonymously and assigns a randomly generated number to recognize unique visitors.
_gid1 dayInstalled by Google Analytics, _gid cookie stores information on how visitors use a website, while also creating an analytics report of the website's performance. Some of the data that are collected include the number of visitors, their source, and the pages they visit anonymously.
Advertisement
Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns. These cookies track visitors across websites and collect information to provide customized ads.
CookieDurationDescription
mailchimp_landing_site1 monthThis cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp_user_email1 monthThis cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp_user_previous_email1 monthThis cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp.cart.current_emailThis cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
mailchimp.cart.previous_emailThis cookie is used to keep track of newsletter sign ups and client emails at checkout, Mailchimp utilises cookies to store information captured from user input for remarketing purposes.
Others
Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet.
CookieDurationDescription
woocommerce_recently_viewedsessionDescription unavailable.
SAVE & ACCEPT
Powered by CookieYes Logo