: Marshall Amp Mods
 

what are you looking to accomplish? I like to do the following (but it varies from amp to amp)
 
1) change the bright channel coupling cap to 0.02 uf (darker/warmer tone)
2) either remove the bright cap or change it to a lower value like 250pf of 500pf
3) change the 'dark' channel bypass cap from 330uF to s something lower (anything from 10 to 100 uF)
5) change the 10k resistor in the PI to something like a 22k or more to balance thigns a bit more
6) use smaller value filter caps, such as 32uF instead of 50uF
7) make sure the .68uF cap is on the cathode of the cathode follower stage...
-- if you have a 70's superlead, or newer (such as a plexi reissue)... throw in an OEI output tranny.
 
.... another one I"m playing with more these days, is changing the 220k bias feed resistors 1o 100k or so
 
Other mods people have recommended on here:
1) change the presence cap to .68uF
2) play with different value feedback resistors
3) bigger coupling caps to the power tubes
4)If the person uses strats/tele's almost exclusively, you may want to change the tone stack to match the bass amps (56k slope resistor, 250pf treble cap)
 
 
 
.... do one at a time, and notice the results, and go with whatever your ears tell you is best!