Hi there,
Just wondering, would it be ok to run -12/13v to an EL84 and then never touch the bias again? I know some amplifiers do this with EL34s/6L6's (eg mesa boogie) but would it do for EL84s? I have a 15w PP amp on a PCB that has no easy way of setting any kind of bias, but it wouldnt be hard to modify the bias supply with a 12v zener instead of a trim pot.
Ricky
Just wondering, would it be ok to run -12/13v to an EL84 and then never touch the bias again? I know some amplifiers do this with EL34s/6L6's (eg mesa boogie) but would it do for EL84s? I have a 15w PP amp on a PCB that has no easy way of setting any kind of bias, but it wouldnt be hard to modify the bias supply with a 12v zener instead of a trim pot.
Ricky
OK if you are happy with one or both of: short valve life, poor sound.
Alternatively, use a bypassed cathode resistor. This is the established engineering solution for reasonably accurate, emission compensating, zero-adjustment biasing.
Alternatively, use a bypassed cathode resistor. This is the established engineering solution for reasonably accurate, emission compensating, zero-adjustment biasing.
ok, why would colder biasing make valve life shorter? if never found the sound of biasing slightly colder (a few mA) that bad.
Fixed bias means the valve is likely to be either too hot or too cold. Either can cause poor sound. Too hot also means shorter life.
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