Xcalibur255
Headphoneus Supremus
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Nearly all of this seller's test values are at about this range so I have to wonder if perhaps they're not using/reading their tester correctly.
The Reference 6J5 Thread (L63, 6C5, 12J5, 6P5, etc.)
- Thread starter chrisdrop
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mordy
Headphoneus Supremus
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I do want to point out that measuring tubes is one reality and using tubes is another reality. Recently a fellow headfier, who owns a newly refurbished and calibrated tube tester, bought a lot of 8 NOS tubes. All tested very good, except for one tube that measured below minimum good.
Based on my own personal experiences, I asked him to put in the best measuring tube and the one that measured below minimum, and do a listening test to see if there was a difference between the tubes.
To his own amazement he reported back that he could not hear any difference! This accords with my own experiences. Unless a tube suffers a catastrophic failure such as arcing over, losing vacuum (turning white) or being dropped and broken, vacuum tubes are pretty hardy and can last a very long time, especially by people who frequently change the tubes lol. It seems that even poor measuring tubes can function well - perhaps such pairs need more volume after a long time, but they may not be ready for the dust bin so fast.
I know of people that have used the same tubes for 10 years or more, and there was still life left in them.
It appears to me that most amps do not drive the tubes that hard so as to wear them out quickly. Personally, I am not afraid to buy untested old tubes - it is rare that there is a real dud there. After all, if somebody has been saving a tube for 50 years or more, it may be safe to think that they did not save a defective tube.
There is one exception though - old tubes used in TVs. Human nature being what it is, I think most people left the TV on the entire day with the resultant excessive wear on the tubes.
I would be interested in other people's opinion regarding this topic...
mordy
Headphoneus Supremus
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The amps that have the C3g pentode sockets can easily accept adapters for 6J5 family and 6J7 family (different adapter) tubes and thus become very versatile.I've only read 23 of the 69 pages so far but noticed a few folks that had their C3G sockets swapped out. Are the C3G yesterday's news and displaced by some new (I should say OLD) tube(s) or shiny objects?
The C3g tubes are great tubes but require careful power tube matching to get the right synergy.
bcowen
Headphoneus Supremus
I don't disagree with you on this -- the proof is always in the listening. But I've also had situations where the musical presentation sounds "off" (lifeless, dull, lacking dynamics, etc) and after testing the tubes in play found one or more that were testing close to or below minimum (GM-wise). Replacing with some fresh ones returned the music to its former glory. I think it's dependent as well on the amp or component in use -- some are more sensitive (or are more dependent) on the tubes amplification than others. On the flip side, the KR 300BXLS's in my Jota amp are the original tubes that came with it....20 years ago. Probably close to 10k hours on them. They still test above minimum at this point (although the Hickok doesn't do a very thorough job at testing a 300B), and I have a replacement pair that I pop in every now and then just to see if there is any marked sonic difference. As of now, I can't tell any difference at all.
mordy
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Wow!
CAJames
500+ Head-Fier
I'm not an expert, but since this is the internet it isn't going to stop me from expounding.
The thing with transconductance tube testing is you're basically asking the impossible: pick one measurement at one operating point from the entire phase space of possible cathode currents and plate voltages to determine if the tube is "good." And in the case of the audio tubes we all love so much this is especially tricky because in most (all?) cases audio was an afterthought and the tubes were designed with some other application in mind. In general I'd say the engineers at Hickok etc. have done a remarkable job solving the impossible problem, but I think it is fair to say that the results from a tube tester are more a guideline than a rule. No one is going to die if one of the tubes in our headphone amp fails, so I agree the best test is to swap with a new tube and listen for differences. That said, I'm not buying (or at least not paying full price) for tubes that test close to or below the good level on my TV-7.
The thing with transconductance tube testing is you're basically asking the impossible: pick one measurement at one operating point from the entire phase space of possible cathode currents and plate voltages to determine if the tube is "good." And in the case of the audio tubes we all love so much this is especially tricky because in most (all?) cases audio was an afterthought and the tubes were designed with some other application in mind. In general I'd say the engineers at Hickok etc. have done a remarkable job solving the impossible problem, but I think it is fair to say that the results from a tube tester are more a guideline than a rule. No one is going to die if one of the tubes in our headphone amp fails, so I agree the best test is to swap with a new tube and listen for differences. That said, I'm not buying (or at least not paying full price) for tubes that test close to or below the good level on my TV-7.
CAJames
500+ Head-Fier
I like 6C5G Fivre (black base) tubes
Bella!
CAJames
500+ Head-Fier
I've said before I think the Fivre tubes look like Spumante bottles, so it seems like we've got something for every taste. 
Looking for a quiet pair of metal base Sylvania 6 or 12j5s. If anyone has a pair they can part with lemme know.
Have you checked around Ebay yet?
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