I don't like the tone of no negative feedback in a plexi circuit, but I
do like playing with reduced negative feedback. I've used pots to
dial in my favorite NFB settings then hardwire a switch to go
between 2 settings, I call it the "viscosity switch". I settled on the
values of 47K standard setting and 150K inserted into the line for a
total of about 200K for the high viscosity sound. I found with less
NFB than that it just all turned to mud, in my opinion. For a great
clean setting I like a 33K NFB resistor, 27K makes it too sterile.
 
Kelley