Preamp Eats tubes..


I own a sonic Frontiers line-3 preamp.The unit eats up NOS tubes.I tried Brimare and matsushita's both within 2 or 3 months the tubes started going microphonic on me.I put in the origanal Sovtek tubes and they work fine.Why does this happen with older style tubes?Are the sovtek tubes built for a tougher demand?
spaz
it's possible that the NOS have slightly different specs and aren't a good match for the SF circuit. my CAT pre is picky that way - it also likes the Sovteks better than some NOS I've tried.
It could be that your preamp does stress the tubes, so that only truly rugged tubes, like the Sovteks, can handle it. It may be that your preamp, is similar to the Audible Illusions preamp that is mentioned by Joe, of Joe's tube lore fame.

The following is a portion of Joe's Tube Lore, which is on Audio Asylum.
(I hope it is okay to post this hear, as it is only a portion of an article, and I gave proper credit, I think.)

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Special warning to Audible Illusions preamp users:

The one you can say for the Sovtek is that you can run it hard and it can take it - and apparently that’s exactly what AI does. Unfortunately the classic NOS tubes in this family just cant take this kind of treatment and will rapidly fail when used in these units (and some of you guys have the fried tubes to prove it!). So you AI users are probably best off limiting yourselves to the Sovtek, the Russian 6H23N & 6N1P, the 7DJ8 and the E288CC. There may be others the range of tube types and variations is quite literally bewildering but these are the ones I’m aware of that should be able to handle the higher stresses of this brand of preamps. I review the Edicron, Siemens E288CC and 6H23N here but there are other brands for some of these. I’ve seen Phillips E288CCs & Amperex 7DJ8s advertised on some web sites in the past and there are probably others. It might be worth your while chasing them down & evaluating them for yourself to increase the number of alternatives for use in your AI.
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(I don't know for a fact that your preamp is over stressing the tubes, but it sounds like from what you write. Good luck in your search for the magic tube for your use!!)
i know there are big changes nfrom my SFL1 and your unit, but I leave mine on 24/7 and have atleast 8 months on a used tube a fellow Agoner gave me.