Cryo tubes

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Purpleplexi

Well-Known Member
I was a bit unhappy with the power tubes in my lovely Carr Mercury. It was like after about 20 minutes of playing amp went dark sounding. I'd replaced the preamp tubes already so I got a pair of these -

6V6GT STR-TAD CRYO

The TAD 6V6GT STR Cryo is a special Cryo treated version of the TAD 6V6GT STR. TAD have based this 6V6GT design on the oval plate RCA and GE 6V6GT of the late 50s early 60s. The round anode plates have extensions on them which form heat wings that will help the plates dissipate more heat. TAD...
www.watfordvalves.com

Never bothered with cryo tubes before but I liked the idea that they stay bright when overdriven - I don't like it when the driven sound loses it's clarity. Anyway everything they say in the blurb is true - these sound great. Realised the old ones were date stamped 02 which was about 15 years before the amp was built so I guess whoever traded it in stuck some crappy old tubes in it before they sold it. Tsk.....
 
Fresh valves will sound better if the old ones are worn. The cryo stuff is complete nonsense though. In a century of vacuum tube production including development for military use, there's never been a single indication that it's in any way beneficial. If cooling them that far had any effect (which is highly unlikely), the effect would likely be reversed once their heated again to the 700C+ they reach during operation.
 
I never knew these even existed. It seems like they may become more uniform and last longer?

I’m starting a new company we’re Play Boy bunny’s hold the tubes between their boobs for 20 minutes, rotating them at the half way point. It does nothing for the sound, but watching them being made will melt your heart. ❤️

Each set will come with a copy of your tubes being made….. $485 for a set of “fairly” matched tubes. (No pushing or shoving)
 
One thing I’m not sure of is, if Tatiana, (one of our… a…. technician's) makes a set, are they now considered Russian tubes? Very technical… I’ll get back to you.
 
While it may coincide with a perceived preference, the black coating on the plates was actually intended to enhance thermal properties (radiation in this case), not to improve frequency response or any other aspect of the valve's performance. They also experimented with the dark heaters which were intended to be more linear inspite of wild ambient temperature swings and - if I recall correctly - slightly varying filament voltages. Ultimately, the cathode coating would be the 'interesting' one of the bunch as it's the component emitting the electrons.

I would certainly agree that black plates look cooler, though. Pun not intended but I'll go with it. :)
 
PelliX said:
Fresh valves will sound better if the old ones are worn. The cryo stuff is complete nonsense though. In a century of vacuum tube production including development for military use, there's never been a single indication that it's in any way beneficial. If cooling them that far had any effect (which is highly unlikely), the effect would likely be reversed once their heated again to the 700C+ they reach during operation.
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Either way I've decided to call the amp `Walt`. Only other time I've encountered the cryo thing was in my Subaru tuning days. You could make so much torque with them that they would eat the second and third gears. The solution was to cryo treat the new gears before reassembly. I never did it but it was well regarded and pretty much `de riguer` if you were drag racing. I considered it and there's a company near here in Kimbolton who with pretty much cryo treat anythiing.
 
This is why I don't have single ended amps. There's something disturbing to me about one big output valve and two little preamp ones. Prefer a pair of big bottles anyday.
 
Purpleplexi said:
Either way I've decided to call the amp `Walt`.
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Sorry, I feel I'm missing a reference here...?

Purpleplexi said:
The solution was to cryo treat the new gears before reassembly. I never did it but it was well regarded and pretty much `de riguer` if you were drag racing.
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I've heard of this, too. I might well stand to reason that it can somehow reduce the likelihood of fracturing in such applications, but that relates to mechanical strength. A valve doesn't operate 'mechanically' in that sense and heat is not only a byproduct but a vital part of its operation. I could imagine that it might help to perform extreme heating on the cathode of the valve before applying the coating due to thermal expansion, but that's a guess at best. As for freezing them after they've been put together, de-gassed and sealed it seems pointless - in fact *if* these companies are really giving those valves the treatment (and that's nearly impossible to prove, ultimately... [wink]), it might have a negative effect on the plastic bases or the adhesive used in applicable types (6V6, EL34, KTxx, etc, etc). Hmmm, next time I snag a base off an old one, I might just try some liquid nitrogen... the last one involved a lot of hacking at bits of glue and broken glass before I could remove the wires...
 
PelliX said:
This is why I don't have single ended amps. There's something disturbing to me about one big output valve and two little preamp ones. Prefer a pair of big bottles anyday.
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My single ended Victoria eats some of the NOS power tubes for lunch. I can get anywhere from weeks to months, Sometime a year if I
m lucky. That combo amp is like a torture chamber for tubes. I think there are a few different reason for this that I can expand on later.

There is nothing wrong with the amp. I got 3 years out of the Tungsol reissue 6V6 before I started to loose it's steam. The
JJ 6V6 lasts a while too. But I prefer the TS reissue.
 
Ouch, have you taken a voltage survey and/or checked the dissipation? Is it cathode biased by any chance?
 
PelliX said:
Ouch, have you taken a voltage survey and/or checked the dissipation? Is it cathode biased by any chance?
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The 5112 only runs one power tube. It's cathode biased. The wall voltage runs between 119 and 122. The amp
is supposed to handle 125.

I talked to Mark Baier about this,he thinks the amp is okay. It's the older NOS type tubes that are hit and miss. I think
some of those tubes may be rated for 110 volts. But they should be able to handle a little more.

The tubes will start to rattle. Sometimes the low G note would sound like the speaker is blown. But it's the tube. I'm
talking about those old RCA smoked glass tubes from the 40s. Same with National from the same era. Sylvania too.

Some last longer than others. I've had better luck with the big bottle Marconi. They seem to last a littler longer. I'm fine with the new
production Tungsol reissue. No issues with the JJ.

My amp can also run a 5881 power tube with a 5ar4 rectifier. Here I use real USA tungsol. Never an issue. I push the crap out of the amp
too.

Oh and one for the tech guys Fryette has an interesting take on the old NOS. I don't know if it's ok to copy and paste from another forum or post a link. Until I find out I can send you a PM.
 
blues said:
The 5112 only runs one power tube. It's cathode biased. The wall voltage runs between 119 and 122. The amp
is supposed to handle 125.
Click to expand...

OK, the real question is what input voltage is required to get the filaments at 6.3V. That's the best reference. To be honest, +/-3V from your wall supply is very little, consider yourself fairly lucky, hehe. Have you checked the filament voltage at all?

blues said:
I talked to Mark Baier about this,he thinks the amp is okay. It's the older NOS type tubes that are hit and miss. I think
some of those tubes may be rated for 110 volts. But they should be able to handle a little more.
Click to expand...

The limiting voltages would be the heater and anode, really. "NOS" just means unused, it's not an indication of any spec or quality. If we can determine which factor is causing the faster failure rate, it might be that a given type of valve may provide a longer service life.

The key factors here are plate voltage, filament voltage and dissipation. Cathode biased amps are often biased relatively hot to accomodate a wide range of valves, but with the downside of running others extremely hot, particularly single ended. In some cases swapping the cathode resistor is the best move overall, but to comment on that we would need the numbers first.
 
Purpleplexi said:
It's said that Walt Disney or a least his head has been cryogenically frozen and sits in storage waiting until technology can bring him back to life.
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He’s in my freezer next to a pound of bacon , I leased a spot for him to mini mouse. (What a piece of….oh, never mind) About a month ago I hit the plug vacuuming, although he has kinda a droopy (no pun intended) shocked look on his face now, I think he’s ok. I’m no doctor, but I did comb his hair and put on a new zip lock freezer bag.
 
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