Life span 6BQ5 tubes
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trainbuftony
Electron Herder
I would think that after 3 to 5 years of regular use they should be checked more closely for bias, and at that point it would be prudent to have a new set in hand in case they start to show major differences.
62vauxhall
Addicted Member
Jim McShane sold me a cold matched quad of Sovtek 6BQ5’s. But that was before Putin began flexing his weenie.
trainbuftony
Electron Herder
Try them all they're still relatively cheap in comparison with the octal power tubes.
AmadeusMozart
Well-Known Member
And depending on how it is being used it can be a lot less. Some guitar amps barely make the evening.
Many do not realise that for a constant pure sinus signal the maximum Pa is 9 Watt continious. Due to these tubes being about the cheapest in the past (as a result of mass production) many amplifiers run these tubes beyond their ratings. (Buyers always look for more power - bigger is better: NOT! Biggest nonsense there is, most listen at 1 watt or less...)
Using Pearl-Hifi or IERC tube colloers you can extend the life of those tubes 50% to 100%, it can be even more if you use a stabilised mains +/- 3% of the filament voltage with slow start (gradual warm up of both filament and afterwards of B+) Very worthwhile on something NOS that is rare, e.g. 7591, 7868. I'm up to 6000 hours with some 7868 with no sign of deterioration and have read of people having them already running for 20000 hours with no sign of deterioration.
The 300B was designed for 100 000 hours (when not switched off and run within specifications in class A).
Metal fatigue happens with continual bending of metal, and the same with tubes: With quick heating up and cooling down you get metal fatigue of the internal materials. Slowly does it.
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You can still get those Soviet tubes for not too stupid costs. Mostly they come from Ukraine or one of the other former USSR satellites now. The 6P14P or 6P14P-K are the less spendy ones, the -EV cost more because they are rated for a bit more abuse. If you've been running these for years without them dying I'd say you don't really need the heavy duty version. Prices are all over but I've seen matched quads for 50 bucks shipped, and "used, tested, strong" quads for under 20 shipped.
no idea how well matched they are. The ones I got years ago were matched in the sense that the boxes were all the same. Date codes and internal construction wasn't quite identical and electrically they were all over the map. I've had that with other tubes too though, so its not uniquely a Soviet tube seller thing.
no idea how well matched they are. The ones I got years ago were matched in the sense that the boxes were all the same. Date codes and internal construction wasn't quite identical and electrically they were all over the map. I've had that with other tubes too though, so its not uniquely a Soviet tube seller thing.
Lavane
Lunatic Member
I would think it depends on what soviet Era tube you use. Same with Tube depot or anywhere else, it probably depends on The tube manufacturer.
The Russian tubes I bought to replace the same with in a guitar amp seemed to uave held up well. The Sovtek EL84M's in my ST-35 are doing great. That amp gets a lot of use too. With the Russian tubes you do have to pay attention to the lettering after the tube number if your looking for the more rugged versions.
The Russian tubes I bought to replace the same with in a guitar amp seemed to uave held up well. The Sovtek EL84M's in my ST-35 are doing great. That amp gets a lot of use too. With the Russian tubes you do have to pay attention to the lettering after the tube number if your looking for the more rugged versions.
AmadeusMozart
Well-Known Member
IIRC: The -K has the shortest lifespan of 1000 hrs.
Lavane
Lunatic Member
Someone posted hours for the various 6P14P tubes in post three in the link below.
https://www.diyaudio.com/community/threads/russian-6p14p-tubes.106326/
https://www.diyaudio.com/community/threads/russian-6p14p-tubes.106326/
AmadeusMozart
Well-Known Member
As far as I know the K was vibration proof. It may be that the vibration shortens their lifespan and that in a non vibration environment it lives longer, don't know.
See also my previous posting of datasheets
https://audiokarma.org/forums/index.php?threads/using-7189s-in-place-of-6bq5s.1011994/#post-15994471
https://www.diyaudio.com/community/...cation-of-various-brands.298616/#post-4871419
Lavane
Lunatic Member
The 6P14P-K is probably pretty much the same as the 6P14P, just made to handle more vibration. I've seen the 6P14P-K's listed as a special audio version of the 6P14P. Whatever that means. They do sound nice though. I saw one listing claiming the K's being sold were used in Ukrainian submarines.
