[Lkdog]

Probably stupid question and I apologize if covered before.

I have a VAC Standard LE preamp.
It uses four tubes in the driver section (12AX7 and 12AU7 pairs). Also some in phono stage.

I see tube life often  listed in hours like 10,000 for small preamp tubes.

If I leave it on 24/7 that is 8760 hours a year.
Of course they are sitting idle except for 2-3 hours most days.

Do they degrade over time? How does one know?

As a guitarist- I turn off the amps when not playing and small preamp tubes last forever unless they go bad.
I was not sure what happens in high fi audio world.

Thanks for info.

[mick wolfe]

Turn it off when not in use. No advantage to leaving it on from a performance standpoint. A tube pre-amp will warm up and sound just fine within 15-30 minutes. All you're doing is shortening tube life.

[jjss49]

yes they degrade if left on, regardless if music is played or not through the preamp

iirc vacs run tubes are the hot/hard side

i would say retubing will be needed in under a year

but why leave on when not listening?  not a good idea with tubes

[Speedskater]

A half century ago, at the radio stations, almost everything used vacuum tubes. While it depended on the circuit design, most small tubes lasted a few years 24x7x365.

[JakeJ]

There is absolutely no good reason any vacuum tube equipment should be left on 24/7/365.  I can think of one good reason to not leave tube gear on all the time is the possibility of a component failure causing a fire.  Never leave tube gear on unattended and if you are sleeping that's unattended.

[nature boy]

Depends. Some of the NOS preamp tubes could give you 10,000 depending on the preamp design. Modern reissues maybe 5,000 - 6,000 hours. I would not run tube equipment 24/7 personally, it's just asking for trouble.

NB

[richidoo]

Audio Research used to recommend changing small signal triodes (6922) at 4000 hours. It starts to lose body after that. Even though it might work until 10,000 hours, the performance level needed for high end audio is gone and it will get more thin and strident over time.

Since preamps don't have output transformers it doesn't take a long time for them to warm up and sound good, so it's better to shut it off when not listening.

The performance requirements of hifi tubes is far greater than for instrument amps. A slight degradation in the stereo is very noticeable, but a guitar amp can tolerate more tube wear before becoming a problem.

[FullRangeMan]

Run tubes around the clock is real dangerous, not tô mention a lighting during a rain or a fire. Also small transformers cant run many hours, they get hot due small cores.

[Lkdog]

Thanks for the input.
Have not noticed any apparent sound degradation, but I also may have just adapted to the sound over time.
I have extra tubes I can swap out so I might be surprised.




EDIT- Ok, I stand educated. I had some time tonight to take the lid off and swap out the 12AX7 pair (Chinese) and the 12AU7 pair (NOS CBS 5814s)  in the line stage which had been on 24/7 for better part of the last three years.

First thing was the very low level hiss that was present in the noise floor if you put your ear up next to the speaker was gone. Dead silence.
Overall sound quality change was apparent across the spectrum, especially low end extension. I will not bore you with audiophile terms. It is better.

The 12AU7 pair is a decent NOS Amperex miniwatt pair. I think I paid about 100$ pair for them a few years ago.

The 12AX7 are a TAD select pair I had laying from some guitar amp build. As noted they are quiet.


Thanks guys. I will turn it off from now on.