2. amps-preamps
  3. 1218975014

tube burnout

I have owned a tube pre (Grant 100) for a few years and have been satisfied with the sound generally. My concern is that it eats up tubes. It takes six 6922's
with two of them in the mm phono and the others in the linestage. I have gone through about two dozen tubes in the last few years, and it does not matter what brand tube it is either.
This almost always happens to the phono tubes where they start out fresh, only to discover a month or two later these tubes start to get noisy. When replaced,
I get a month or two again before the noise starts up again and they must be replaced. While this is going on, the other four tubes in the linestage are not affected and play fine on any source other than vinyl.
I have tried 6922 from most manufacturers including new and NOS.
I had the pre checked and they said it was fine, just bad tubes to be replaced.
Which I did, and did, and did. All to no avail.
Still the problem persists. I can't believe that all the tubes I keep installing
are 'lemons'.

Does anyone have any suggestions?
tessera
blindjim
2,837 posts
 
Changed tube vendors? Changed tube makes? New ones and used ones, and still it doesn't seem to matter as the results persist?

yep... I'd say the pre is a lemmon... despite the statements of the maker.

If it walks like a duck, and looks like a duck, and swims like a duck, it ain't a water tight chicken... it's a duck.

Sorry to hear it, but sure hope it works out for you.
tessera OP
20 posts
 
Hi guys,
Rar1
I allow the pre a few minutes before playing music, at low volume for the first twenty min to half an hour. This goes for the amps as well.
Spencer
I am leaning towards this way of thinking also. I believe that somewhere, something is feeding the phono tubes more voltage than necessary causing them to slowly deteriorate.I am not an electronics tech though.

Tessera
tessera OP
20 posts
 
Blindjim

Yes I tried different vendors
tube makers
new ones,NOS, used
still it does'nt matter
rleff
1,065 posts
 
Are you on conditioned power? If it were me; I would be looking at ac power or the pre amps' own power supply.
tubeo
72 posts
 
You might try a 7DJ8 . It's 7 volt rating makes it more robust and may withstand being pushed harder better . Also Tungsram 6922/6DJ8 type tubes are known to last longer than others of this type when pushed hard .
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