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What would happen when you under Bias your tubes?

Hi, I am a tech noob and I always wanted to ask if it is safe to under biasing tubes and especially the power tubes? Will that affect performance or will that do damage to the amp? I am asking because my power amp which is the Lamm ML 2.1 has manual bias and when I left the bias unchecked for awhile. It somethings jumps much too high then originally set and those 6c33c doesn't last! I mainly set the bias to 70%. Is that OK? Thanks.
luna

Showing 2 responses by mozartfan

mozartfan
2,143 posts
 
 I mainly set the bias to 70%. Is that OK?

Yes ALWAYS under bias. 
= Better tube life, less risk at blowing a  power tube. 
70 is OK
mozartfan
2,143 posts
 
no

not if you want proper sound the amp maker intended

~~~~~~~~~~~~~~~~~
At the risk of buring tubes faster than he wishes. 
I tell my tech guy, bias  low, 
Richard beinga   tech perfectionist, does not like  biasing low, So we compromised after his *as specs biased* blew a  cap (Mundorf $50!!) + had to buy a  pair of tubes,, although only 1 tube went bad due to blown cap, . He said order  a  matched pair. 
My amp sounds perfectly fine biased a bit lower than specs require.
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