OK, so I'm having some issues, maybe, with biasing. I'm ending up with some strange results, seems to me. I'm basically seeing max headroom with max source resistance (20k). I am never able to see symmetrical clipping, regardless of trimpot settings. It's always the bottom that flattens out first, and backing off the source resistance only makes the bottom of the wave worse, all the way until the FET shuts off.
If I back the trimpot off to about 18.2kOhm, I can improve the distortion such that for a 200-300 mV input signal, or thereabouts, I see below .5% THD on the output, which seems reasonable enough to me (but then again I'm a bit clueless as to what to expect). Moving off of this particular bias point it either direction results in more distortion. The source-ground voltage I'm seeing at these higher source resistances is only about 4.5V, which is miles off of the 10V or so I thought I should be expecting.
Any of this seem reasonable to anybody, or should I be hunting for problems somewhere in the build? Should I seek a different FET that might be closer in spec to what one might usually expect? Any comments/advice will be appreciated.
It seems to me that i had the same experience. Just set for minimal THD as you did before and you should be good.
Thanks. I appreciate your input. Right now, adjusting for minimal THD is the plan.
I'd be interested to hear whether anybody else has ended up with this seemingly extreme trimpot setting and/or low source voltage.