Driver Tubes 6922

Unfortunately I have also received tubesI thought were used ....  not from Brent but another well respected dealer.   

The truth is that a lot of "NOS" tubes are "pulls" , tubes that were lightly used but still test stronger than new.  In the 50's and 60's tons of test equipment and medical instruments had tubes.   When these instruments were decommissioned those tubes were pulled and went into someone's stash.   

I repair medical equipment and still occasionally come across really old power supplies that are tube rectified and filtered.  It was common practice to pull tubes out on a lot of stuff before trashing it 

You could have and probably did receive NOS from Brent but another problem is that after 50 or 60 years the silkscreen flaked off.   Sometimes just touching the print will wear / wipe it away.   

The only way to know you are getting a good tube is to test it.   I ultimately ended up buying a tube tester.   I have a buddy who does clean outs and occasionally he will drop off some tubes.    The last tubes he gave me that I believed to be NOS was a pair of early 60's RCA 6v6.   The boxes were rough but the tubes tested strong , better than min.    Were they used briefly and put back in a box ?   No one will ever know...   

Personally for the 6922 I would just buy a pair of Gold Lion or JJ that is matched and tested for noise.   Its only a few bucks more but you know you are getting new, strong tubes.  

I'm sure Brent will take care of you.   I have had a few tubes from him and they were always as described.  

I bought a tube tester last year and it was an eye opener.   Most tubes I got from trusted dealers were as advertised but I had a number of tubes that were duds. 

Mismatched triodes, weak,  also had a bad 5r4gy (shorted) that would have damaged my new 300b amp.    That tester paid for itself that day.  

My reasoning to buy it was because I was starting to play with antique tubes like 300b and 274b / 5r4gy  types .    That amp also uses e180f  which is only available as NOS or used.    Fortunately that tube and it's variants are easy to find NOS but I want peace of mind before using ANY tube.    That said, even brand new tubes get tested before going in any of my gear 

OK,

I have been in contact with Brent and I trust he is a professional. I tried the tap fix for flake and it did not change anything. I will try that one more time.

And my 6922's are GL's.

Next time Im at the cabin, Im going to visit this junk yard up there and look for tubes :-)

T

Tony, There are a lot of tubes sold on ebay as NOS that aren’t There are a lot of lightly used tubes that still test above average new.

Without going too far into the weeds, tubes are usually tested for transconductance to determine how long they will last and to match them. Tube testers, Hickok is the most common brand, come with a scroll that tells you what the average transconductance is for a new 12AT7 tested on that machine.

Nobody has kept track of which tubes have been used and which haven’t. So if a tube tests above average new and the glass and pins look clean, many sellers will sell it as NOS. Others will sell it as "tests above new" but not call it NOS. There have been discussions about how to categorize old tubes that test above new but probably have some use as ANOS, i.e. almost new old stock., but that never got anywhere.

Tube dealers like Brent Jessee or Vintage Tube Services (Andy Bouwman) use more sophisticated testers than the Hickoks I mentioned above, although Hickok did make lab grade testers which are much more precise than the more common Hickok 600s or whatever.

Even with all the uncertainty, many people still feel it is worth it to buy vintage tubes because they had the same experience you did. They like the sound better. There is a LOT to know about vintage tubes, so you’re better off dealing with someone like Brent or Andy than trying to learn it all yourself.

I read about a test someone did on the web, that had several calibrated Hickok testers and got a different reading from ever one of them.