"adjustable bias" - this is actually called Fixed Bias (yeah, great naming convention, I know).
within the realm of 'auto bias' there are many possible ways to do that concept. Same with fixed bias - eg. separate bias power supply, winding, or tranny, various rectification schemes for bias supply, battery-biasing, etc.
bin:
biased with a scope? What the hell are you talking about? Bias is a voltage, nothing more or less. A good voltmeter is all that is needed. it's either accurate or its' not. There's nothing to graph on a meter. Tech's must have been having a laugh at your expense, methinks.
-Ed