Tube bias...

Wolfenstein98k

Wolfenstein98k

Power User
Long story short, I read an article about some amp tricks employed by a certain scrappy young guitarist to get his Super Lead to have the gain and tone he needed... One such seeing was "diming the internal bias setting".

What seeing in the Axe would replicate turning up to full the bias knob on an amp?
 
Tube bias in front panel controls next to sag or Power Amp Grid Bias in axe edit. Increasing tube bias increases idle current to virtual power tubes giving smoother distortion and fuller clean tones, Reducing tube bias to make the virtual tubes "colder" results in a thinner tone and edgier distortion. EVH is rumoured to bias his amps cold! Many prefer the fuller sound of hotter tube bias
 
I think one needs to distinguish between two things, that are named bias concerning power tubes. On the one hand there is the idle current running through the power tube, when no signal is present (Anode current) and on the other hand the voltage between grid and cathode (when no input signal is present), where the grid has a negative pre (bias) voltage. So it's better to avoid the term bias, because it's sometimes misleading. Either idle current or grid to cathode voltage. My guess is that the Power Amp Grid bias on the Amp Block settings refers to the grid-to-cathode voltage, whereas Power Tube Bias sets the virtual idle current.

Hot biasing is: a higher idle current and a less negative grid to cathode voltage (e.g 80 mA, - 40V)

Cold biasing is: a lower idle current and a more negative grid to cathode voltage (e.g 10 mA, -60V)

There is no nominal cold or hot bias setting in general, the values depend on the surrounding circuit.

It is worth reading the Tech Notes thread on Power Tube bias: http://forum.fractalaudio.com/threads/understanding-power-tube-bias.79049/
 
You must log in or register to reply here.
Back
Top Bottom