Hi Rowdy, fully agree with you.

In fact, I
do use Fets a lot, and have for years.
But I spend all of 30 seconds extra and
bias them.
My heart hurts when I see somebody "copies" some classic tube design (hey, the idea is excellent, by itself)
but places a 1k5 resistor source to ground "because Fender did that" or a 2k7 "because Marshall did that" or even worse, 820 ohms, which is poor biasing (too hot) even on a tube amp.
That's just magic thinking.
Then everybody lies to himself thinking that they have a 100K "plate" resistor, "just as the original did".
Fact is, that is a 100K
trimmer, and the actual resistance value they set to "bias" (really they do not set bias but load) is way below that.
I encourage you to build any of those stages, and post the actual "plate" resistor value set. You'll see it's nothing like 100K.
Fender , in fact, did get those biasing values from 12AX7 datasheets, which precisely state, for around 250V supplies, 1k5 cathode and 100K anode resistors.
You change +B, you change those values, there's nothing magic or immutable about that.
You change tube type, they also change (just read the datasheets).
Imagine what happens when you do not even use tubes but Fets, which to boot vary a lot from unit to unit, and to change things even further, use 9V !!!
Then those 820, 1K5 or 2K7 resistors lose all meaning.
Of course, the allmighty 100K trimmer comes to your rescue !!! ... sort of.
I fully agree with "spending a little time biasing a FET stage or two ",
precisely that's my point !!I think that the right place for those trimmers is source to ground, because there they become real "bias" trimmers; of course I suggest using 10K trimmers.
Another way to do that (which I use) is buying a few extra Fets and Protoboard a simple test jig and get the
actual bias voltage needed , then label them, and later use the right source resistor to get that voltage.
It takes 30 seconds per Fet.
As you see, I encourage
actual testing, not superstition or Mojo .
There's even a simple sound test I suggest:
build a 12AX7 stage, with 1K5 resistor on its cathode (bypassed by 10uF), 100K on its plate, +250V (the real Mc Coy); and a 9V powered Fet stage, with the same value resistors (well, using a 100K trimpot) , with grid and gate connected to the same 1M resistor to ground and an input jack, outputs taken from identical .047uF x400V Polyester caps , DC discharged to ground through 1M resistors to avoid popping; then hook your guitar, play a chord and switch back and forth between both outputs. An MP3 or even a You Tube video would be very useful.
Good luck.
