Re: Fender Bassman and Sunn 200s preamp pedals.

Posted by Frank_NH on Feb 04, 2016; 12:52am
URL: http://guitar-fx-layouts.238.s1.nabble.com/Fender-Bassman-and-Sunn-200s-preamp-pedals-tp25184p27775.html

According to my JFET spreadsheet, for a 1.5K source resistor, the optimal drain resistance for a "typical" 2N5457 is only about 7K!  So a 100K trimmer is overkill.  You can use a 20K (or even a 10K).  Try to get about 4.5V - 5V on both drains.