Originally Posted by: RazboWhat does NOS mean with regard to tube amps?

Acronym for New Old Stock.

http://www.audiotubes.com/nos.htm

http://www.davestechshop.com/pages/faq.htm#q3

I've heard this is supposed to apply to only old tubes that were manufactured years ago (pre 1970s), are currently out of production, but are "new" because they were never actually used. But I've heard engineers complaining about some shysters claiming they have NOS tubes, when in fact it is newly manufactured stuff made to look like actual NOS.

I am not sure how much difference it would make if you could actually make something brand new that mimiced precisely what an old tube did. But obviously I wouldn't trust someone that was not honest about their product anyway.

In my experience, guys that work with this stuff frequently use an old tube model or stock as a standard (6L6, 12AX7, etc.) to measure a new tube by, but aren't above or against using a newly manufactured tube.

However, the NOS issue can be the cause of much debate & discussion!

http://www.thegearpage.net/board/showthread.php?t=713301