Plexi Mods - Marshall Amp Modding Secrets!

2205/4210 Gain Mod

You may know changing component values in your amp can radically alter tone. But changing component composition can also change your amp’s tone. These mods will increase the overall brightness and perceived clarity of your Marshall amp. Do them one at a time and judge the difference for yourself at each stage.

1. Changing all the 12AX7’s plate resistors to 100K’s except the Phase Invertor & Reverb tube. This will make the amp more “touch-friendly” and more Marshall’esq. This will also take the “buzzy” tone out of the amp. It does reduce the gain so if you want more gain see #2 and #3.

2. Locate the 10K cathode resistor (R13 found on V2) and place a .68uf cap across it. This will increase the gain A lot!. It also boosts the mids nicely to get that sweet Marshall “crunch”. If you’re into classic rock, you may not want this cap on there. If you like “heavier-tones” then run with it.

3. Locate 1.5K cathode resistor (R16 found on V2) and replace it with an 820ohm. This will increase the gain slighty and make the amp a bit more responsive (depending on if your amp matches one of the two 2205/4210 schematics avalible)

    Note: All resistors are 1/2watt unless otherwise specified and caps/resistors are marked according to the Marshall schematics.

thanks to schematic heaven for the above mod

Related posts:

  1. 2203/2204 Tone Mod
  2. 2203/2204 Tonestack Mod
  3. V2a Cathode Switch
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