Concern about Voltage/bias with 5998 tung-sol tube

[Veri]

Hello everyone. I have been listening to the amazing bottlehead crack for months but have recently upgraded to a 5998 tung-sol tube.

The seller sent two 5998 tubes, one sounded perfect/amazing/divine, the other was in worse shape, had glass parts inside it and sounded noticeably worse. With both tubes tough, I had a few gassy sparks the first time I used them, but now it hardly ever happens (burn-in?). I ask him to get a refund/partial refund for the glass shard damage and he is saying that my amp (the bottlehead) "is designed around the 6080 which is not equivalent to the 5998. The bias set up needs to be different. The sparks are not good and can damage the amp, tubes, your phones or worse your ears. The newer 5998s from svetlana (winged c) may handle more voltage."

I thought the 5998 were the preferred tube for the bottlehead though? (if one can afford/get them at least). Is the tube seller right / wrong? Can bias be adapted for safer usage with the 5998 tube?

Thank you for any help,
Regards and thanks

[Paul Birkeland]

Glass shards loose in the tube isn't damage and I wouldn't ask for a refund for that.  This is something that isn't uncommon in tubes, and it could be a little piece of glass between the bottom of the tube and the octal base.  There isn't anything wrong with this really.

How about performing a voltage check on the amp to see how it's biasing up?  No changes need to be made to the stock circuit for the 5998 to work just as well as the 6080. 

[Raymond P.]

Veri,


Would you mind describing how the problematic tube sounds worse? Curious.


Thanks,
Raymond

[Veri]

I can't rule out 100% that it is in my head, but one has much more pleasing sound than the other. Low end is the same, but detail/smoothness of sound is different. The seller admits that he used them himself for a "really long time" so one might just be in better shape than the other?

A voltage check has been done before on this unit and everything checks out. And huh, didn't know loose glass isn't uncommon. Never had a tube before with loose glass.

[JamieMcC]

Small bits of glass in the bottoms of 5998's are quiet common and it should not effect their sonics. You could check that none of the bits have gotten stuck in the plate structure whist they have been rolled about during shipping.

[Veri]

Thanks for the information. Note that I bought them for quite a hefty price, which makes me feel like the loose glass could have been mentioned in the auction before I paid for and received them. But glad to hear it should be fine. I'll do some more A/B testing to see if they really sound so different, or that I'm going insane I could send one of both back I suppose, but I figured I could use a spare. What's the lifetime of the average tube, before it no longer functions? Does one need more than one in a lifetime