Pre-amp tubes life span

[JulesDB]

Hello,

according to some people you must change 12ax7 tubes every two or three times you change the power tubes.

I read on a site that their life span cannot be determined and could be almost infinite so that they could be changed only when you want to change the tone of the (pre)amplifier.

Who's right?

 

[psychodave]

Depends on the tube. NOS can last 10,000 hours. They had stricter standards and tolerances. New tubes are a crap shoot, but I understand they typically last 5,000 hours (??). Their manufacturing standards are a lot lower and thus, performance will vary.

 

[Dave L]

Preamp tubes can get noisy or weak at any point from the second they were made, so you often have to switch them out for other reasons than actually breaking down or nearing the end of their considerable life span. There´s no reason to switch them out regularly as a sort of scheduled maintenance, though, unless you hear a problem they´re fine.

 

[CornNutz]

Just keep an extra set on hand. Switch them out only when needed.

Signs of a bad pre tube:
crackling
poping
lower volume
no volume
flub
screeching/microphonic

If you get any weird stuff like that its easy to take 1 new tube, and try it in each spot to see if it make the problem go away

All modern 12ax7 tubes will fail at different rates, i.e. you might buy a new set and 1 fail in weeks, while the others last 10 years.

Just replace the one that goes bad.

 

[311splawndude]

only replace when needed or to mess around with tonal changes

 

[maddnotez]

Probably longer than youd have the amp. That's why to me spending $100 on a really good NOS 60s tube isn't so bad.

 

[311splawndude]

Probably longer than youd have the amp. That's why to me spending $100 on a really good NOS 60s tube isn't so bad.

That's my man. Posting like a true gear head

But just make sure you pull those NOS tubes out when you sell/trade away right?

 

[psychodave]

Probably longer than youd have the amp. That's why to me spending $100 on a really good NOS 60s tube isn't so bad.

That's my man. Posting like a true gear head

But just make sure you pull those NOS tubes out when you sell/trade away right?

Steve K and I would talk about how stupid we were flipping amps and leaving in the Winged C power tubes.

 

[Samhain]

Every amp ive sold had 100's of $$$ worth of NOS/CP glass.
I know folks usually put crappy tubes in an amp when selling but when i voice an amp & get it where i like it thats how its sold.
But thats me.
Another reason why i retube every amp i buy regardless of what the owner sez.

 

[311splawndude]

I'm not a flipper but if I was - I'd keep my NOS and just put in a known good array of JJs. Pretty much can't go wrong there and of course, I'd make sure it sounds good. Sometimes, if I'm tube swapping (for tone) and I get wrapped around the axle I know I can always revert back to a JJ.

Are they as awesome as NOS? No.
Are they a great base standard? Yes.

PS: Just noticed my Phillips JAN 5751 that was a PI in my Splawn has black getter so that's about 10 years. Light use I'd say too if I'm honest. Can failing power tubes cause a PI to die faster?[/u/]