2203/2204
Find the 68K input resistor (R3) and place a 330pf 1kv ceramic cap across it. Beefs up the
mids and lows
Change the 10K cathode resistor (R6 found on V1B) and replace it with a 4.7K resistor. This
will give you more gain, but if you want more still, try a 1.5K.
Locate the 820ohm cathode resistor (R9 found on V2A) and place a .68uf cap across it. This
will increase the gain a little, but will mostly give you a mid range boost.
I personally find that just changing the 33K tone slope resistor (R15) with a 56K sounds
awesome in almost any Marshall. JCM800's are certainly NO exception! While you're at it,
change the treble cap from a 470pf to a 250pf. Both of these bring the brightness down, and
bump the bottom and mids up.
If you want a darker tone overall, try this one:
Change C1 (.68uf cap) which is found on V1A and replace it with a .47uf cap. This alters the
midrange response.
You can also:
Replace the 470k Ohm resistor that is tied to the input tube grid with either a 68k Ohm, 34k
Ohm or 10k Ohm resistor. The lower the resistance, the darker the tone, but 68k is the
"classic" value. (Don't be tempted to remove this resistor altogether). It has to be there to
attenuate the grid circuit and prevent excessive overload conditions.
Remove the 470pF cap which bridges the 470k Ohm resistor you just removed.
