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Post subject: Re: cryo treated tubes
Posted: Mon Dec 24, 2012 7:30 am
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I also want to thank bluesky636 for his evaluation.

I started with a pair of Cryoset EH 5751 preamp tubes, using one in position V1 of my HRDlx and comparing to an untreated EH 5751. While both tubes sound decent, both lacking in the high-end sparkle, I noticed no difference in sound on the clean channel, and just a little smoother tone for the cryo tube when using the drive channel, which could easily be attributed to the difference in gain between the two tubes. The first cryo tube that I tried went microphonic fairly quickly, but being a long Plate tube this was almost expected, so it might or might not be due to the cryo treatment. I think that I will save the other cryo 5751 for other amp positions.

I also have to say that there was no "wow" factor for the cryo tube compared to the untreated tube, they sound virtually the same. I still have a pair of cryo treated 6L6, and an untreated pair that I will test in the next few days and post the results when finished. The review by bluesky636 coupled with my 5751 test doesn't leave me feeling as positive about the cryo 6L6 as I was before, but I will check them anyway to be sure. I guess that if we had the time and money, we could see if any other vendors are doing a better job with their treatment, but it is difficult to evaluate so many types of tubes, and even more difficult to test any long term benefit of whether or not the cryo tubes actually last longer.

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Gotta love the "everyone knows" nonsense. There are a lot of statements that start like that, usually based on zero personal experience. :lol: I believe that "everyone knew" that the world was flat before Columbus. :wink:

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Post subject: Re: cryo treated tubes
Posted: Mon Dec 24, 2012 8:09 am
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I think I was disapointed more by how poorly the Cryoset tubes were matched then by the lack of any noticable change in sound. As I vaguely remember, even the original Groove Tubes (Sovtek 5881WXTs) that came in my BDRI were better matched than 4 mA. Maybe 4 mA is not bad (I know Mike K from KCA NOS Tubes uses 3 mA as his standard match with 1 mA match costing a few dollars more), but compared to the Eurotube versions that cost less and match better, it does make me question the Cryoset basic processes.

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Post subject: Re: cryo treated tubes
Posted: Mon Dec 24, 2012 10:40 am
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99.9% people say cryo is bs! you all should know that:)


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Post subject: Re: cryo treated tubes
Posted: Mon Dec 24, 2012 9:10 pm
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bluesky636 wrote:
I think I was disapointed more by how poorly the Cryoset tubes were matched...4 mA...


I agree, that isn't matched very well in my book either, it should be closer. Really, matched should be matched, meaning the same, and I'm disappointed if more than 2 mA difference, and I will usually send them back if more than 5% difference. Uh-oh! Another mod idea for your BDRI....a balance pot. :o

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Post subject: Re: cryo treated tubes
Posted: Tue Dec 25, 2012 5:51 pm
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shimmilou wrote:
Uh-oh! Another mod idea for your BDRI....a balance pot. :o


Nah. Although I did briefly consider one for my 5F6A clone build. :D

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Last edited by bluesky636 on Sun Jan 13, 2013 1:04 pm, edited 1 time in total.

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 12:59 pm
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I've spent a considerable amount of time comparing the cryo treated 6L6 tubes to the untreated 6L6 tubes, switching back and forth four times, four separate days to be sure, and I can say with certainty that there is a noticeable difference in sound between the two. I used two of the quad of cryo treated JJ 6L6 GC tubes in my HRDlx (the other two of the quad tested by bluesky636), and compared them with an untreated pair purchased at Sam Ash. The set from SA had the same Maxi Matcher number as the treated tubes (19). Both sets of tubes were biased to 40 mA Cathode current (each tube), 430 Plate volts. Both sets were rechecked for bias after an hour or so of use, both sets drifted a little and both sets were reset to 40 mA and remained steady after that. Mine were much more closely matched than the pair that bluesky636 got, within 0.2 mA of each other. I used a hum-bucker equipped Strat at first, then switched to a single coil Strat for the majority of the testing time.

The first thing that I noticed was that the treated tubes were noticeably clearer on the clean channel, with a little better high-end response and sparkle compared to the untreated tubes. Not a huge difference but definitely noticeable, the untreated tubes sounded slightly dull by comparison, much like the "blanket over the speaker" analogy. When switching to the drive channel, the difference was much more striking. The treated tubes had much smoother distortion, and a much warmer, richer tone compared to the untreated tubes, almost as if the bass had been turned up instead of distortion, although the distortion was present. I verified this by using a signal generator and scope and saw that the treated tubes had a slightly later onset of distortion, just about two to three numbers difference on the drive pot. It's difficult to see exactly when the distortion starts, but the difference on the pot setting was obviously not that close. The distortion of the treated tubes wasn't as gritty or crisp as the untreated tubes and this might not be to everyone's liking. For the setup that I use, I kind of preferred the grittier distortion of the untreated tubes, but the warm, rich distortion of the treated tubes grew on me after awhile and it was very pleasing as well, just different. The clarity of the treated tubes on the clean channel was definitely preferable for me.

It would be nice to be able to compare many more sets of different brands and types, but this test was enough to show me that there is a difference. Maybe this difference is better suited to hi-fi amps, but I can see that it could be beneficial for instrument amps as well, probably largely dependent on taste. :idea:

If I were to guess from my reading of reviews, I'd say that 75% or more of the people that actually try the cryo tubes notice a difference, and prefer the cryo tubes, whereas 99.9% of people that never tried them tend to dismiss the claims. I have also heard that 80% of all statistics are made up on the spot, so..... :lol:

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 1:09 pm
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Interesting results. However, it is impossible to conclude that the difference you heard was due to the cryo treatment or simply because they were a set of tubes from a different production run than the untreated tubes. You would need a much larger sample and double blind testing to draw any real conclusions.

An interesting comparison would be to run both sets of tubes through a tube tester and compare their measured parameters.

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 1:31 pm
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Yes, this is a only small sample, not exactly the last word, and the two of us have mixed results, but I'm not sure that I want to invest that much time and money. I do have an amp with EL34s, so maybe we can do this same test again soon, perhaps after you finish your new amp build. I can't wait to find out what it is. :wink: I can definitely run the 6L6 tubes through my tester and see what differences, if any, show there. Will do later tonight, but time for a nap now as I'm exhausted from playing with my new tubes, new guitar, and new amps. :D

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 1:48 pm
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IMHO, you're better off spending the extra dough on better NOS tubes than the expense of trying to make a JJ tube sound better. Kind of like putting lipstick on a pig vs. taking Miss USA to the dance...

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 3:15 pm
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Bendix Red Bank was given carte blanche to make ICBM and B-52 needed tubes in the 1950s. And they came up with the most exotic materials and designs and charged the US Government up to $50 per tube! In the days when RCA was charging Fender 25¢ per 6L6GC.

No where in Bendix white papers is there any suggestion of using cryo treatment. And their tubes had to withstand 100G's and -50F temps. And still function. I'm certain that liquid nitrogen was around in the 1950s. And the merits of low temp-low resistance was already known.

Anyhow, if you EVER get a chance, the Bendix 5992 (6V6GT type) and their 6106 (slow-start 5Y3WGT) are awesome tubes. I put a set into a Vibro-Champ (must be 20 years ago, now) --- and I just got off the phone with that owner. Still gigging with that amp and same Bendix tubes.

I've also built a couple DIY guitar and hi-fi amps using the Bendix 6094 (cross between an EL84 and 6AQ6).

6900 are super linear gain stage tubes. Even more linear than the Holy TS 5687. They make great pedal tubes. Very quiet and smooth linear OD tone. There are some nice DIY OD pedal kits that use this tube. In the Matchless Hotbox vein.

These tube were never meant for guitars or hi-fi. But, by far, have the best tone and life of any tube I've ever used. And that includes TS 5881 and 6550. Or GE 6550A and STR-415 (7581A). Just looking at the internal structure is something else.

http://www.vacuumtube.com/issue5.htm


Bendix 6889 and 6384 (6L6GC type --- different pinouts)

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Bendix 6106---5Y3WGT type

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Bendix 6094--EL84 type with different pinouts

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Bendix 5992---6V6GT

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 6:27 pm
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nedorama wrote:
IMHO, you're better off spending the extra dough on better NOS tubes than the expense of trying to make a JJ tube sound better. Kind of like putting lipstick on a pig vs. taking Miss USA to the dance...


:lol:

Well, brand opinions aside, this was about cryo treated vs untreated, nothing more. I chose JJ because they are relatively inexpensive, and the cryo treatment only added about $20 more for a quad. Although, I was happy to finally put my GTs back in.

BMW2002Ti,

Virtually no one was cryo treating anything in the 50s, except maybe roses in classrooms. :lol: It was barely in its infancy back then. Besides, there is much more to cryo treatment than dipping something in liquid nitrogen. It's affect on metal is quite well known now, it isn't witchcraft, it's science and there is an affect on metal when treated. If you consider the fact that metal contracts when cooled, imagine how much it contracts and is compressed when super-cooled for a time period. How much that will affect the tone of a tube might very well be subjective, but so far I see nothing that can contradict the claims of the affect on the metal. I've noticed at least a smoother distortion in two types of cryo treated tubes so far. The difference in the 6L6 was like two different brands, at least as far as distortion characteristics. As bluesky636 pointed out, it might require some more testing and data review to know what exactly is happening, and using identical tubes from the same batch, half treated and half untreated, might be more definitive.

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 6:48 pm
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nedorama wrote:
IMHO, you're better off spending the extra dough on better NOS tubes than the expense of trying to make a JJ tube sound better. Kind of like putting lipstick on a pig vs. taking Miss USA to the dance...


I find nothing wrong with the sound of the JJ 6L6GCs from Eurotubes I use in both my BDRI and 5F6A clone. I'll be using JJs from Eurotubes in my next amp build which will be EL34s.

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 7:52 pm
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Checked the 6L6 tubes used for my testing on my Eico 667 tester with a current probe between tube and tester.

Untreated pair:
114% - 92 mA Cathode and 116% - 94 mA Cathode

Treated pair:
118% - 98 mA Cathode and 120% - 100 mA Cathode

(edited for correct current readings)

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Last edited by shimmilou on Sun Jan 13, 2013 9:41 pm, edited 1 time in total.

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 8:05 pm
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shimmilou wrote:
Checked the 6L6 tubes used for my testing on my Eico 667 tester with a current probe between tube and tester.

Untreated pair:
114% - 9.2 mA Cathode and 116% - 9.4 mA Cathode

Treated pair:
118% - 9.8 mA Cathode and 120% - 10 mA Cathode


Sorry. Not having a tube tester myself (would like to get one, though), I'm not sure what that means. Please explain. Thanks.

What would be a useful, but not too expensive tester to get?

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 9:23 pm
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Well, as I understand it, the Eico is a "Dynamic Conductance" tester, somewhere between a simple "Emission" tester and the patented "Mutual Conductance" tester. Many say that the Dynamic is just as good as the Mutual, with the exception of the absence of the Gm reading. Hickock had the patent on the "Mutual Conductance" circuit, so Eico and some others used a similar circuit but with AC voltages, and no actual Gm numbers, as opposed to the DC used on the Hickocks with actual Gm numbers. The leakage tests on the Eico are basically an emission test, with each element tested selectable by the push-buttons (representing tube pins 1 to 12 and C), using 70 VDC for each element tested, with the other elements grounded (virtual diode), while the conductance test uses a selectable AC voltage on the Plate, screen and grid. The selector switches connect the tube's pins to their proper voltage taps (representing tube pins 1 to 12 and C), the meter and ground or no connection. For the 6L6, the voltages that I used are; 160V on the Plate, 90V on the screen and 30 volts on the grid. The meter scale shows an ohms value for the leakage tests and a percentage for the conductance test. The Eico is particularly useful for finding bad tubes, and very good for matching and strength tests, and much better than a simple emission tester as the Eico uses much higher voltages and more closely simulates operation in an amp. So, the readings that I got indicate tubes are in good shape and the relative strength of each for comparison. The leakage tests are done before applying the high voltages to the tube, and if the leakage resistance is too low, no need for further testing as the tube is bad. I have found bad tubes that passed the leakage tests (emission test) but failed the conductance test. So, a simple emission tester would have passed the bad tubes.

All things considered, the Eico is just as good a tester as any almost any other, better than an emission tester, and is one of the easiest to use with no complicated calibrating or setting procedure such as required for most Hickocks. You can usually find good used Eico 666 and 667 for under $200 on eBay and other places, the 667 is preferable for instrument amplifier tube testing. The only knock on the Eico is the inaccurate information on the roll charts for some tubes, but usually comes with supplement book with better settings, and once you learn how it operates you can make your own choices for the voltage settings. They never did get all the info correct on any version of the roll charts over the years (about 8 revisions). Pass on the ones that don't come with the manual and supplement book. I did a ton of research and found that the Eico 667 was perfect for testing the tubes most commonly found in guitar amps, and the Hickock models that are "Mutual Conductance" testers are usually much more expensive, more complicated and offer no real advantage except for giving the Gm of the tube.

I've been eying the modern Amplitrex tube tester, which seems to be the ultimate in testers, but costs about $2600. I think it is worth it as it can connect to a computer and do some very complex testing automatically, including giving the actual Gm of the tube being tested. Apparently the Hickock "Mutual Conductance" patent has expired.

Here is a shot of my tester, 1967 vintage and in excellent condition.
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Another shot of it in action, testing an extra JJ 6L6 GC tube that I previously used in my C600. The readings show about 120% strength and 105 mA of Cathode current, shown on the Fluke meter.
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:oops: had to edit my previous current readings, I had them off by a factor of 10. What was I thinking? 0.105 amps is 105 mA, not 10.5 mA. :oops:

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