biasing amz mosfet boost?

[rpjones]

A beginner's question: I read somewhere that when biasing the mosfet by adjusting the 100k trimmer, the bias voltage should be 4.5 volts with the circuit idling (no signal present). Does this mean that the circuit is turned on by plugging a jack into the input but the bypass switch is in the off position? I ask because when I have 4.5 volts with the pedal bypassed, I get about 4 volts when it is switched on. I know this may seem like an obvious question, but I am new at this stuff, so I appreciate your indulgence.

Thanks

[Jay Doyle]

Bias it when it is in the 'on' position. You may also want to mess with the trim a little while playing with it, you may find a sound that you like better a little off of 4.5V.

Jay Doyle