Question about replacing tubes in amplifier

[Vlad_demokrat]

Hello everyone!
I want to know by what signs (in addition to time intervals) can you understand that it is time to change the tubes in the amplifier?
And how do I know if the tubes in the preamp tubes or amplifiers are out of date (in my case with Diezel vh4, can I diagnose this by inserting guitar into a common loop or loop for each channel separately and thus separating the preamp tubes)?
Thank you all in advance for your answer! ;-)

 

[Ventura]

Mmmmmmmm, no true methodology other than a) a tube red-plating/arcing/blowing during play (noticeable), or b) swooshes and swishes and volume fluctuations (usually preamp related but not always) and thirdly c) age and number of hours (and intensity of those hours) in use. Often one doesn't really realize they need new tubes until they put new tubes in only to realize how much crisper the amp sounds and reacts. But that's also assuming good tubes were chosen for the job. I've got some amps that are regular players that have had the same tubes in them for almost 10 years (true story), and others where I'm still mixing and matching the glass to get the sound I want.

Physical failure or signs leading to such are swooshes and swishes in the sound with no playing needed to hear it, popping and crackling that's quite loud (power tubes), or just a dullness/muffled kinda feeling you get when playing which is just age.

(One can also always de-chassis the amp and check bias points for drift and see that all tubes are within range - but this is power tube related more so than preamp; preamp is the swish and swoosh test - usually)

 

[CornNutz]

We'll they work until they don't. No real "out of date" concept.

Now that being said they will degrade overtime, and become weak, or noisy, and as mentioned above power tubes can redplate, but they can do that new as well.

My advice is replace them if/when there is a problem.