ralph, curious to know what is your take on auto biasing... now increasingly employed in high level tube amps, audio research’s newer amps for instance
the feature certainly offers a major convenience factor for users, but what do you see as the tradeoffs or downsides sonically or operationally, if any? (of course we note the obvious add’l cost and complexity of the feature)...
also, does auto biasing get the power tube biasing as precisely correct as manually biasing via multi meter (as arc used to do it for years?)
I see automatic bias as a good thing. The less the user has to fiddle with the amp the better- makes it easier to live with.
If designed right there's no downside except the additional circuitry itself. How precise it is depends on the design; in some circuits the precision is more important than others. So its a case by case basis.
The downside of manual bias is the tube can drift while you're not looking, assuming you got it right in the first place. An auto bias system takes care of that. FWIW, cathode bias is a form of automatic bias. This can makes things confusing, because many autobias systems typically use some sort of monitor on the tube and adjust the bias via the grid rather than the cathode of the tube. For this reason, most modern autobias systems are considered 'fixed bias'.