Disappointing short life of NOS preamp tube

Being sarcastic really.

I only got 7 years out of  50's 12au7 RCA black plate. That may indicate 5 more randomly futzing out the rest of this year.

With the state of tube pricing now, tubes definitely not on my list of unnecessary audiophool spending.

I was really hoping these things going for 20, especially them just being preamp tubes, not a power tube. Fortunately, I have one more for backup, plus the 6 stock tubes in the shoebox.

Such is life. I'm more impressed by my relatively quick troubleshooting, avoiding severe neurosis. Less than 5 minutes-patting myself on the back, and praise from the boss.




I've never  cared/paid attention to tube hours, but the amp /tubes have served me well.

Over the 6 year period there have been random marathon weekends of near 24 hour service, after work, almost daily 2  hour dinner sessions, random times the amp has been accidentally left on weekends(not recommended, of course) and BLAST your ears sessions with friends. 

Whatever it equates to, I consider the tube serving  it's purpose. I have a daily driver 67 Mac tuner  with a couple of original tubes. 

USA NOS tubes for the most part are indestructible, but not 100% like anything manmade.




good old stock 12au7’s are still plentiful and pretty inexpensive, your complaint falls on deaf ears with me... and if you only got 7 years out of your pair, you must be abusing your gear

he he he

As George Harrison said, All Things Must Pass.

I guess you should be glad it was just a tube and not you.

tablejockey - I may be wrong but my impression has been that preamp tubes are rated at 5-10,000 hours. Given your described usage you may have reached that over the 6-7 years

It sounds like around 5,000 hours.

I have heard NOS have long lives… but as a kid also remember taking tubes down to the tube tester at The local drug store. I suspect some over romanticizing. And of course “average life” has a bell curve distribution.

Fortunate that your pre is not pushing tubes hard, considering also the on off cycle.

Sad moment when they go and wonder if the new pair will sound the same.



7 years is a long time for any tubes , plus you don’t know how your amp company bias the voltage or run the Ma voltage , power tubes 3-4000 hours 

small tubes like Tele , Siemens are 10,000 even bendix,  some ge 5 stars are tough military speck,  but nothing guaranteed with tubes , todays tubes far worse.

In 2003 I ordered three NOS Mullard CV4003 (12AU7) for the preamp I was building. Average about 16 hours per week for roughly 16000 hours to date and still going strong. I tested all my tubes last month and these three still have close numbers. I have a backup set of Sylvanias that I'm not sure I'll even need in my lifetime. 😀

"It sounds like around 5,000 hours."

ghdprentice- I''m  thinking the tubes are now somewhere in the 5-7K zone, so yeah

I'm not surprised to see one futz out now. 

Anyone remember buying the 5 pack when they were "new?"


When you look at it from that perspective, This journey and or hobby isn't really that expensive, When you add up all the hours years of enjoyment you get from a component that you love the sound of, or the synergy of a well balanced complete system, I think it's well worth it,,,,,,,Then again I don't want to pay for any exorbitantly high.prices.

7 years / 5,000 hours is OK. Where’d you get the tube from? Any chance it wasn’t really NOS? To be fair, 12AU7's get a lot hotter than say 12AX7.


Yeah, I figure it was in the upper range nearing 10K hours. As said in the opening post, I'm just goofing on the fact they lasted "only 7 years."

I get most of my tubes from Brent Jesse, and trust his listings. If he say's their NOS, I rely on that.


I get most of my tubes from Brent Jesse, and trust his listings. If he say’s their NOS, I rely on that.

I actually wonder that. Not sure there’s a guarantee of being "NOS", or whether that would even matter except for power tubes. That said, I’ve bought many, many tubes from Brent over the years and I appreciate his service and selection. He’s got lots of really nice exotics you can’t find elsewhere, except for taking gambles on the ’bay. Brent’s tubes always test good and sound great! He doesn’t make mistakes. No bum tubes. He even takes care to generally select clean looking tubes.

If you got 10,000 hours on a 12AU7 I think that falls into "great job, little tube" territory :) 

"I actually wonder that. Not sure there’s a guarantee of being "NOS", or whether that would even matter except for power tubes."

mulveling- yeah, the "NOS" thing is roll of the dice. With preamp tubes, it may not be such an issue whether or not you're getting a genuine, unused "NOS" tube.

True NOS is something you actually purchased  from the local hardware or drug store for $1.87, tossed in a box in storage for the next 60 years, and you "discover" it.

I've been using some 50's  RCA 6L6G's (the low voltage coke bottles) also from Brent that were installed just weeks after the 12AUf7's. One just died the other day.

I'm  hoping to get another batch from him, and refresh all 8 needed. 

I had a pair of 1964 Mazda 6dj8 that came from Brent Jessee and they were matched section, matched pair.   They were some of the best sounding tubes I have ever owned.   Unreal tone , unfortunately the preamp they went in is tough on tubes so they didn’t last as long as expected but man did they sound good 

About six months ago I bought a 12at7 from Upscale, from Kevin’s Stash    It was a Mullard 6201 and it sounds incredible.    

The above dealers are a safe bet   

I have an amp that is a hybrid, It uses both sides of one small signal tube a 6DJ8 on the input (no need to match tubes) and the output uses power transistors. A ridiculously good sound. In this scenario the tube will and does last a very long time and the amp has been powered up 24/7 for best possible sound. Initially I have tube rolled with different brands that have produced dramatic results. It is nice to be able to tailor the sound for my speakers and for my own own tastes.