Look at the C2, R5, R1, R2, R3, R4, R6, R16, C1, C7 and Q1 section. What I am sharing is a high input resistance NPN transistor gain stage that can be used instead of a JFET stage. I adjusted C1 to .68uf for more a low end bump note the change with .68uf to 10uf in the graphs. I even have the gain controlled to about x14.4. The tone pot is being simmed at different places in the rotation for the different curves. You could adjust the gain up by swapping R2 and R16 about x26
IMO a well designed bootstrapped BJT circuit is more repeatable without transistor selection than simple JFET circuits.
You can often drop in different transistors Si and even Ge and the bias should be in a workable range with out trimming if you need to trim you can adjust one resistor in the bias section.
I have posted other circuits at this forum with sims and do not seem to get much of a response.
If R.G. or Mark posted something like this would there be more response?