Cryo Tubes

Discussion in 'Home Theater Projects' started by Don*A, Mar 19, 2005.

  1. Don*A

    Don*A Agent

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    Anybody out there have any knowledge of Cryo Tubes. I have a Shanling CD player. I am using WE 396A Tubes and was thinking about upgrading to Same tube but cyro treated they are just 3x the price of the ones I have and would like some thoughts first.
     
  2. ChristopherDAC

    ChristopherDAC Producer

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    In my research I have never turned up any reason to believe that vacuum tubes, items which operate inherently at a high temperature, would be altered at all in terms of their service characteristics by exposure to the moderatly low temperatures employed by most "cryo treatments", except that differential thermal expansion of metal and glass could concievably break some poorly-made tubes. On the other hand, I cannot see how using a thermionic voltage-amplifier stage fed from an integrated circuit input stage, and particularly a digital-analog converter, would be any advantage; so I would suggest doing what makes you feel happy, and you will experience the psychological effect of an improvement in sound quality even if the measured characteristics actually get worse. If you really want to improve your system's performance, you can analyse the voltage amplifier circuit, figure out what the critical characteristics of the valves are, and [using an appropriate test instrument] test a large number of tubes of the same type until you find the best ones for your application; or procure a tube manual and find a type with similar characteristics superior in the respects you require.
     
  3. Chu Gai

    Chu Gai Lead Actor

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    Chris makes good points. Something else to consider. A vacuum tube is composed of several different components which due to the nature of what they're made of, will have what's known as thermal expansion coefficients. In layman's terms, this means that depending what something is made of, it will expand or contract at different rates when subjected to heat or cold. In the case of cryo treating, which is probably taking the tubes down to liquid nitrogen temperature, a very real effect that happens is that you get internal deformation of the components inside the vacuum tube. Further, this deformation may be permanent which will alter the electrical characteristics of the tube. Even if you rebias the tubes, the electrical characteristics are likely to be somewhat different. The net result is that your sound will change. You might like it, you might not, or perhaps the cryo treatment will shorten the life of the tubes.
    If you're into tubes, then just go out and buy different sets from different manufacturers or get into NOS.
     
  4. Don*A

    Don*A Agent

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    Thanks for the feedback, Here is some info from a company doing this. I am new to tubes and alot of this does not make sense to me you both seem to know what your talking about, would like your thoughts Thanks

    An Overview of the Treatment andGrading Procedures of Cryo-Valve tubes

    The series of operations through which an electron tube must pass before it
    can be called a "Cryo-Valve" is lengthy and in some ways, arduous.

    First, only the best sounding NOS (new old stock) and new production tubes are considered
    for cryogenic treatment. Every tube is pre-selected by Tube World on a "SOFIA" computer curve
    tracer and only the tubes with the most linear and evenly spaced plate curves are
    selected for cryo-treatment. Also, in the case of dual-triodes such as 12AX7, 6922,
    only the tubes with the closest triode section matching (typically within 5%)
    and quietest noise-floor are chosen for treatment. Pentodes such as EL34, EL84, 6550
    are selected on the basis of having high transconductance and high standing idle current
    and are matched into pairs and quads before they are frozen.

    As received, a typical electron tube exhibits several problems that directly
    impact its sonic performance. Most serious are the many internal stresses in the
    construction materials that accumulate during most of the stages of manufacture
    and; a very hard, heavy oxide-coating on through-glass pins to which direct
    connection is made. Seven and nine-pin miniature tubes are typical of those pins
    which are heavily oxidized while power tubes such as KT88 and EL34 are fitted with
    bases whose pins are tinned with the result that contact quality is much improved.
    The degree of sonic improvement is SUBSTANTIAL.

    The initial 100 hour burn-in allows the tubes' characteristics to stabilize while
    providing an opportunity to "cull" any "infant mortals"

    During cryogenic tempering, the tube is slowly cooled to the -117 C / -320 F
    temperature of liquid nitrogen, "soaked" for many hours then slowly returned to
    ambient. By means of this unique and vital process, the stresses interior to the
    materials of the tube are substantially and permanently relaxed. During a
    subsequent, high temperature anneal, the tube is heated to a 175 C / 350 F
    temperature then slowly cooled to ambient. Although not as extensive, the
    results are similiar to those achieved by the cryogenic procedure.

    The "Q" of the (self) resonant (electro) mechanical systems responsible for the
    output of (self) microphonic spuriae is therby drastically reduced. By this
    important reduction, both the peak amplitude and the "ring down" time of these
    systems is reduced with the result that the "apparent gain" of the tube is
    increased - even in feedback controlled circuits - while the "dynamic noise
    floor" is lowered.

    Grading for noise and microphonic performance involves both listening and
    intrument evaluation. Various instrumentation provides data on the noise,
    microphonic level and spectral content while the overall "sound" of the spuriae
    is critically evaluated. In particular, the evaluation of microphonic output
    is very much an experienced-judgement call.

    Dual triodes (example: 12AX7, 6SN7GT, 5751, 5687) are rated for overall noise
    performance by the noise-output level of the noisier "tube" or triode section.
    Thereby, it's possible for a tube given an over "STANDARD RATING" to contain an
    ultra-low noise (ULN) section. ULN rated tubes however, always consist of two
    ULN sections, hence the higher cost per tube.

    The last few steps in the process are the standard yet essential procedures for
    the evaluation of many important electrical characteristics such as GAIN, PLATE
    CURRENT and TRANSCONDUCTANCE. Additional data is generated indicative of the
    GAIN and DC BALANCE of each tube's sections.

    Quite simply, "Cryo-Valve" electron tubes are the tube of choice for virtually
    all high performance audio applications: your satisfaction is guaranteed!

    Each tube has its own "serial number" and comes with test data for:

    * Noise Grade: Standard (+5db to 0db)
    Low Noise (0db to -3db)
    Ultra Low Noise (-3db to - 6db)
    Gold Grade (-6db to -8db)
    (0db=input noise of 1.3uV: - 3db at 10hz and 30Khz)

    * Microphonic Test: Output Level (high to low) and Ring Down (slow to fast)
    * Plate Current: (ma)
    * Triode Section Balance: Idle (DC) and Dynamic
    * Triode Section Gain Match
     
  5. Chu Gai

    Chu Gai Lead Actor

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    And compared to a non cryo'd tube, this costs what? Money back if not satisfied?
     
  6. Don*A

    Don*A Agent

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    Regular is about $80 a pair. Cryo are around $250.
     
  7. Garrett Lundy

    Garrett Lundy Producer

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    Yargh! I've culled many an infant mortal in my day.
     
  8. Chu Gai

    Chu Gai Lead Actor

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    Well I don't know exactly what to say here Don. It seems that the cost of the tube is related to several factors...
    burn-in to weed out problem tubes
    electrical testing to group the tubes
    cryo treatment
    temperature annealing (I wonder if that's done in a regular oven?)
    additonal electrical testing

    Certainly the person's time must be compensated for as well as the cost of the equipment. On a side note here, how certain are you this outfit actually has a LN2 temperature controlled setup? This isn't exactly inexpensive. Maybe you might consider dropping them a line suggesting that you'd be in their neighborhood on business and ask about a tour of the facility. Not an unreasonable request for any business I think. Just see what they say. I'd guess that they'd tell you their facility is proprietary. If so, who can really tell if they actually cryo their tubes or maybe they avail themselves of a friend who works in a facility where he can sneak these things in for an overnite run.

    On a practical note as to whether this is worth it, I'd look at warranty, return if not satisfied, how well the tubes match electrically, and for the burn in process. I think I'd be a little happier if they also did a post thermal treatment burn in.

    You might find this link to be of some interest as it discusses a device quite similar I believe to the 'Sofia' (no longer made if I recall). Perhaps some of the discussion in the review as it pertains to electrical characteristics might be of benefit to you in perhaps asking more relevant questions of these people.

    You know as well as I do, that if you ask around the web enough, you'll find happy customers. All I know is 3x the cost is a lot of money and you could buy 3 pairs of tubes or more that maybe didn't go through the thermal cycling yet were still matched electrically. Good luck [​IMG]
     
  9. Don*A

    Don*A Agent

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  10. ChristopherDAC

    ChristopherDAC Producer

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    The terminology they use is OK, but for the life of me I can't see how the technique they claim to employ would get any kind of results. Freezing and then annealing would tend to increase the residual strains if anything [that is, the freezing would increase the stress; the annealing would relieve the stress by allowing the material to deform, thus increasing the strain], and to increase the degree of oxide deposition. A good solvent-bath cleaning would be a better treatment. As for interelectrode capacitance, it is influenced almost exclusively by the construction of the tube, and cannot be changed much once the getter has been flashed.
    Really, I suspect these folks of employing a good deal of doubletalk. Careful pre-purchase testing of tubes [to test for microphonics, tap on the end of the tube with a pencil eraser and see if the tester needles jump] should get good results. Instead of burn-in, you could try used tubes. I know it sounds odd, but an acquaintance of mine who has worked in radio and television, on transmitters and recievers, since the '30s tells me he has almost never seen a tube go bad from age. Breaking of the heater filament is the usual cause, which is more a function of how often the tube was powered up and down than how many hours it has burnt.
     
  11. Chu Gai

    Chu Gai Lead Actor

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    Well it's hard to say if that's a private address. If so, it suggests that if he's got cryo equipment in his home, that's pretty remarkable. Why don't you press him for pictures, instrument model numbers and the like. On a side note, you might look at your yellow pages to see if you can find any electronic repair places. They just might have tubes laying around for a good price. Also, various audio pro shops (Guitar Centers) have tubes also at incredibly competitive prices.
     

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