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Lifespan of NOS telefunken 12AX7?

Hello,
I just purchased a quad of NOS telefunken smoothplate 12AX7's from brent jesse. I have seen some 12AX7 tubes rated for up to 10,000 hours. These have been some medical grade tubes such as the mullard 10M series. I have some mullard longplate 12AX7's and 12AU7's that I have been using on a regular basis for the past two years. I would say they are getting close to 1200 hours on them. They are still going strong and sound good. I was just wondering what the general lifespan of a standard telefunken 12AX7 tube was. I am using them in a rogue ares phono stage. How many hours would you guess they should last. I understand there is no set number of hours but, I am interested in knowing a tubes useful lifespan. I tried to find some info on google but, I couldn't really find anything that stated a lifespan of standard telefunken tubes. Thanks in advance.

Andy
andyprice44

Showing 3 responses by rrog

rrog
1,958 posts
 
Of course some tubes are hardier than others, but the lifespan will be determined by the equipment and how it is used.
rrog
1,958 posts
 
"Alan- that is quite a surprise. I didn't think a tube could last that long. Interesting."

Audio Research rated the tubes in their hybrid preamps to last 10,000 hours. However, I have never seen a tube manufacturer give their tubes a lifespan. It really depends on the application. That same tube that lasts 10,000 hours in the Audio Research preamp may only last 500 in another preamp.
rrog
1,958 posts
 
Sp-14 is a solid state line stage with hybrid phono using one 6DJ8. As I mentioned previously, Audio Research rated those tubes to last 10,000 hours and the original tubes were Chinese, however, sorted by ARC. All of those hybrid preamps were slow to warm up, but because of the long tube life you could leave it on 24/7 for the best sound and you would only have to replace the tube once a year.
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