Go here to read about and download the Tone Stack Generator (TSC).
http://www.duncanamps.com/tsc/ When you first run the TSC, click on the Fender tab. Next you need to make two changes:
Double click on C2 and change its value from 100 to 47.
Double click on C3 and change its value from 47 to 100.
I believe those are the correct values for the F-1X; I got them from a prior post here in the forum. Don't forget to save this setup once you've made the changes.
I have found this tool to be very helpful in understanding what the settings are doing and how they work interactively.
/Edit
Also; the next time you run the TSC, it will open with the default setup; so you will have to open your saved file to restore the F-1X settings.
(Message edited by davehouck on January 10, 2005)