Einstein pb : bias value not constant.

  • Thread starter Thread starter kunfi
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kunfi

New member
Hello everybody,

I controled the bias of my Einstein. I found it was not setted to 65mA for a pair of EL34.
So I adjust it to 65mA.
The amp sound better it had ever sounds. More thick, more dynamic, more punch on attack.
I control the bias 3 days later. It has decreased to 53mA.
Is there a problem with the tubes, with the amp, with the external bias ?

Thanks for any reply.
 
When replacing power amp tubes I usually bias them up, let it run for an hour and rebias. (It often changes by a couple of mA) Then I retest the bias after a couple of days...
But your reading is pretty much of. It could be a faulty tube. Are you sure the DMM is connected right and has good contact? Please use banana plugs for that. Rebias and let it run. Recheck after an hour or so.

Best.
Stefan
 
It is also a good idea to bias the amp twice. If it was at 53 mA and your adjust the outer pair to 65mA and then adjust the inner pair to 65mA there could possibly be a shift in the bias to even out everything initially. Let it run for a bit and recheck. It will eventually settle in and be fine. :thumbsup:
 
Thanks to everyone.

@Duolos
My einstein is 50W, only one pair.
 
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