How many times do you guys bias your Herberts?

[steve10358]

It seems to me, all I have ever done is bias my amp. I can get it to sound killer, and then like a frog in boiling water... I realize months later that it doesn't sound the same.

So I hop in there, and have to set the bias again. I've got matched tubes (Strb's) and have always had to do this regardless of tubes. I always have to tweak to make it sound how I want it.

Any suggestions? Is something wrong?

S.

 

[scottph]

No suggestion really, but I'm still on my first set of tubes after a year...maybe there is something wrong with yours?

 

[itsme]

Once when I put new tubes in, and then once again a couple weeks later after they burn in. The bias always seems to drop after they burn in. Mine sounds great until they start to go.

 

[guitarobert]

So I hop in there, and have to set the bias again. I've got matched tubes (Strb's) and have always had to do this regardless of tubes. I always have to tweak to make it sound how I want it.

Question, do you find that the current measurement has changed and that you have to raise or lower the bias trim to get back to the original setting (33mA or whatever it was)? Also, after re-biasing do you find that you can get the same sound you had when you originally installed the tubes?

I'm finding I have to change tubes regularly in my VH4, but I never considered that the bias setting may have drifted and can be reset. I figured the tubes were reaching the end of their useful life quickly. If it's just the bias that needs to be adjusted I'd rather do that - it saves money on buying new tubes!

 

[steve10358]

Yeah- I usually have to rebias every month or so. I can hear the amp start to get nasally and know it's time. Happens no matter which tubes, etc...

Peter- any suggestions??