Can you play with the "bias" to alter amp sound ?


Standard Member
My local technician was telling me that my Rotel power amp could use some " bias fine tuning " after few years of use, and that will improve the sound . That's first time I hear of such a thing. Either recession is hitting that tech really hard, that he's coming with new ideas, or just me, missed that info and never heard about it.


Distinguished Member
He's talking about altering the amount of standing current passing through the output transistors,to adjust the amount of Class A operation the amp runs in.

Usually,this is at the level of a few watts or less,as the heat dissipation issues obviously increase rapidly,and with some amps,fan cooling becomes a neccessity,as in the older Krells.

Some current Class A amps use adaptive biassing where the input signal is tracked,and the bias adjusted accordingly,to keep the output stages in Class A at all times,but only using as much current as is required.

This may help...

Adjusting the Bias Of Your Amp [English]


Active Member
If you are interested why not make a deal with him.

Maybe along the lines of -

Fine do the work but if we can't hear the difference then it is free :devil:


Standard Member
Well, what do you know... That report shows that after few years of use , bias could be offset, and affects sound clarity. Even if mine was offset, my ears got used to it gradually over time . So I would rather not mess with it, but now, that I know that there are fine adjustments, I have that thing in my head " you could improve it.... you could improve it..."


Active Member
See if he will chuck in a general service and clean it all up/check everything is as it should be. The only thing is if it's got better with time :D what then!? You'll have to wait another few years to get that back!! Seriously though if I had a nice amp getting old that I intended on keeping for a few more years, I'd pay to get it looked at once in a while, peace of mind if nothing else, so long as it didn't need parts I can't see it being much over £50 or so...

edit: Don't know how I got to this but I just realised it's quite old... Sorry.

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