My first question would be........why 70%?
Different amps seem to like different bias settings. I'd never set a Fender at 70% or anything close to that; they seem to sound their best somewhere between 50%-60%. Some other amps like to be close to 70%. Some are just fine running at 50%.
My advice would be, adjust the bias, listen, go 5% one direction or the other, listen again, then go the oposite direction, listen.
That 70% number is just a "whats typically safe for class A/B" number. Its not a magic number for good tone, and often its not the number at which the particular amp sounds its best.
I'll usually try not to bias any hotter than I have to in order to get the best tone out of the amp. If the amp sounds equally good at 55% as 60%, and worse above or below that, I'd set it at 55%. It will run cooler and preserve your tubes.
Just because you CAN set idle current at 70%, doesn't mean you SHOULD.
Different amps seem to like different bias settings. I'd never set a Fender at 70% or anything close to that; they seem to sound their best somewhere between 50%-60%. Some other amps like to be close to 70%. Some are just fine running at 50%.
My advice would be, adjust the bias, listen, go 5% one direction or the other, listen again, then go the oposite direction, listen.
That 70% number is just a "whats typically safe for class A/B" number. Its not a magic number for good tone, and often its not the number at which the particular amp sounds its best.
I'll usually try not to bias any hotter than I have to in order to get the best tone out of the amp. If the amp sounds equally good at 55% as 60%, and worse above or below that, I'd set it at 55%. It will run cooler and preserve your tubes.
Just because you CAN set idle current at 70%, doesn't mean you SHOULD.
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