nos vs current

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Mark II
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nos vs current

Post by piggyboy » Tue Apr 03, 2012 7:25 am

When i see current production tubes for sale they usally have various options like 'premium tested' etc.
when i see nos tubes for sale they never have these options.
Is this because nos tubes are better built so they are basically as good as the premium selected tubes of today.
and is it safe to swap a 12ax7 for a 12at7
is a 12AT7WA the same as a 12at7


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Re: nos vs current

Post by stokes » Tue Apr 03, 2012 10:37 pm

Any good supplier will test tubes before they sell them.And more likely to test nos than current production,with preamp tubes at least.Current production preamps are usually bought in larger lots and less likely to be tested by the guy that sells them to you.They undergo some testing at the factory,but judging by the amount of failures you see,that testing is questionable.Power tubes are a different story.They are usually sold in pairs,quads,etc so they are at least tested for current draw so they match.A lot of suppliers also grade them for certain amps,like Mesa.Just because a tube says it is "premium selected" as you say,merely means it is selected to draw a given current in a given circuit.There are only a handful of manufacturers today and the tubes are then labeled as different brands,but are all from one of these manufacturers.There are absolutely no tubes produced in the USA anymore,GT was advertising a line that they led people to believe were being USA made,but it was a gimmick.Environmental issues made them stop back in the '70's.
The "12AT7WA" is just a more modern version of the the one marked 12AT7,there is some difference,but it is inconsequential in an amp.The "WA" is merely a suffix used to denote a later version.You will see it in the 6L6 line as well.A 6L6 is the original,metal envelope tube.Then came the 6L6G,the G denotes a glass envelope.Then came GA,GB and finally GC.The GC being the latest version is the one that has the most marked change,being able to take much more voltage on the plate and being able to put out a full 30 watts as opposed to around 25 or so for the others.Shouldnt use a G,GA,GB in a modern circuit designed for the GC.It is safe to swap a 12AX7 and AT7 but it will sound and perform much different.

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Mark III
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Re: nos vs current

Post by crane » Wed Apr 04, 2012 1:20 am

W = reliability (that's why you see that code a lot on JAN tubes)
A = low noise tube, or could simply be a revision version
These are codes for 12A_7 familly
PRS McCarty Soapbar with BKP Pigs90, PRS custom 22 with BKP Rebel Yell
Mark V Head, 1x12" Mesa 1/2 closed (EVM-12L)
Triaxis 2.0 noFat - Quad preamp
Deep modded 20:20 - Bias modded 50/50 - SimulClass 295
Home made amps/speakers/pedals

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