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Biasing signal tubes on a tube power amp/Quicksilver M120

Took possession of a new pair of Quicksilver M120 power amps with the KT150 tube upgrade a few weeks ago, am in the process of break in with about 70 hours so far. About 30 hours in I noticed that a 12AU7 tube had started to flare up when that amp was turned on so swapped that tube to the other amp and it followed the tube, I contacted Quicksilver and he told me that this is not a concern but to please switch that tube back to it's origional amp as the amp was biased for that specific tube, now my question is if I wanted to tube roll these 12AU7 or 12AT7 tubes am I out of luck and what happens when it is time to replace them as they wear out, are my tube rolling days over or are they just limited? What say you?
tooblue
tooblue OP
787 posts
 
@tubegroover , I am replacing a pair of VTL MB125s that are 21 years old, would have replaced with a like set but were out of my pay grade and took a chance on these, am very happy, just really hate break in time but so far have already showed themselves to be keepers.
glennewdick's avatar
glennewdick
702 posts
 
You may want to double check as I do believe i read in another thread that the QuickSilver amps do need the small signal tubes biased when replaced, also if quicksilver told you to put the original tube back into the original spot in the original amp because they biased it for that spot then it would indicate to me that they are biased. I do know many(most) tube amps do not need the small signal tubes biased but you may want to double check, and i'm sure your dealer can do this work for you.
tubegroover
2,279 posts
 
There is no biasing required for the small signal input and driver tubes. 



seikosha
205 posts
 
There is nothing in the manual for that amp about having to bias the input tubes.  Perhaps the output tubes would need to be biased when the input tubes changed and that's what Mike was referring to.
audioconnection
1,015 posts
 
   (((You may want to double check as I do believe i read in another thread that the Quicksilver amps do need the small signal tubes ))

  Balance adjustment for the small tubes should be done by a tech
  using DC voltmeter.
 Best JohnnyR
   
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