2. amps-preamps
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One of my Tubes on the Jolida 301A flickers

I was playing an LP today and noticed that each time a low frequency measure was being played, the sound was distorted. I played the same measure over again several times and confirmed the existence of distortion not previously heard. I watched the tubes while tracking through this measure and noticed that one of them was getting brighter. Thinking that maybe a tube is ready to go, I swapped it out for the adjacent one to determine if this is a tube issue. The same thing happened with the swapped tube. I tried another tube and again the same thing happened.
Has anyone had the same happen to their amp? Can you share what the root cause was?
Thanks in advance.
switchback
switchback OP
19 posts
 
I'll check the bias tonight. Hopefully this will fix the issue.
Also, thanks for the information regarding a lower bias setting translates to more bass.

Thanks
jerrynsr
14 posts
 
switchback,
did a bias adjustment correct the problem ?
switchback OP
19 posts
 
Jerrynsr
Thanks for the advise, the bias adjustment seemed to have corrected the issue.

Thanks again
jerrynsr
14 posts
 
Cool.

I don't know if you tried different preamp tubes in your amp but upgrading the preamp tubes was the first thing I did. I upgraded the 12AX7A tubes to JJ ECC8003 gold
and the 12AT7 to Jan Phillips 12AT7WC.

The results are incredible! The upgraded tubes cost me $81.00
switchback OP
19 posts
 
Jerrynsr, thanks for the info on the tubes. I'm currently running my source to a CJ pre-amp and I believe (need to check) that I may be bypassing the amp's preamp section. I'm wondering if I should use the tubes you recommended on the CJ unit?
Thanks
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