2. amps-preamps
  3. 158704-127647

signs that tubes need to be replaced

I have a pair of Cary Audio Six pacs which i bought used about a year ago. They mate well with my tube preamp and i couldn't be more pleased with the setup i have.  I dont know the number of hours on the EL 34s that came with the amps. The previous owner may have replaced them at one time since they look like they were sourced from Tubeco.I have them biased at the recommended 220 ma. and put about 300 hrs/yr on them. Question is, what should I be looking for (sonically) besides obvious tube failure that would signify the tubes are nearing the end of their useful life? Will inability to maintain bias be any indication?

Thanks,
J.Chip
128x128jchiappinelli
decooney
2,033 posts
 
@jchiappinelli 
Look here for additional signs...
https://www.thetubestore.com/how-to-tell-if-your-tube-is-bad

@oddiofyl 
Interested in your update after you fully burn in the Genelex GL KT77s in your QS amps.  I'm recommending them to a friend for his QS mono 60 apmps in place of the stock JJ KT88s.  
rshak
419 posts
 
My PrimaLuna DiaLogue Premium told me when I had a bad KT88 via the "Bad Tube Indicator" feature.  When a power tube goes bad, the amp goes into protection mode, sound cuts off, and a red LED indicates which tube is the culprit .

I knew about this feature when I bought the amp - and wondered if it really worked.  It does and now I'm a believer.  I don't know if this feature is available on other brands, but I'm glad I've got it on my amp.
ebm
9,311 posts
 
No highs no bass and crappy sound this is why i only have tubes(12ax7,6dj8) in my TW phone stage only.Good luck!!
roberjerman
4,319 posts
 
When the silver getter flashes start turning brown at the edges! Eventually all the silver will turn to brown. That is the sign of "old age" - even though the tube will still work!
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