2 Channel Mod

The Marshall 2203/2204 Master Volume amps, introduced in 1975, were a big step forwards for Marshall. A clean and a distortion channel in one amp! Unfortunately channel switching isn't possible, neither on the amp nor with a footswitch. The guitar plug needs to be plugged from one input into another input. Not very user friendly. The Clean (Low) channel doesn't quite sound a like a true Plexi. The popular Dr.Tube 2 Channel Mod elegantly solves these problems. The amp is modified to two channels (Plexi and Lead), each channel sporting its own Gain and Master Volume, switchable with a footswitch with LED indication.

The Dr.Tube 2 Channel Mod installed on an old London City DEA100 amp.The Clean channel has the authentic Plexi crunch and the Lead channel clearly has the 2203/2204 overdrive, but better. The amp is further tuned and voiced to the per­sonal wishes of the guitar player. The amp can be voiced subtly like a blues amp or more aggresively like a rock amp. A good early EVH "Brown Sound" tone is no problem with this mod.

The Clean Gain potmeter has a Pull Bright function so that the tone can be brightened a bit. The Lead Gain has a Pull More Gain function which kicks in some more gain for a more intense overdrive. The Lead Master Volume has a Pull Channel Switch function just in case you would like to switch channels without the footswitch.

On (Marshall) amps with 4 inputs no extra holes need to be made, except for the LED indication if so desired. On the (Marshall) Master Volume amps with two inputs (2103/2203/2104/2204), two extra holes need to be made in the front panel.

The Dr.Tube 2 Channel Mod can be applied to the following amps:

  • Marshall JTM/JMP 1985 / 1986 / 1987 / 1989 / 1959 / 1992
  • Marshall JMP 2103 / 2104 / 2203 / 2204
  • Marshall JCM800 1987 / 1959
  • Marshall JCM800 2203 / 2204 / 4010 / 4103 / 4104
  • London City / Power City DEA 50 / 70 / 100 / 130
  • And many other classic Marshall like clones...

It is ofcourse very important that the tubes and electrolytics are fresh and in order. If this is not the case then these (and other worn parts) will need to be replaced. Some electrolytics will be replaced anyway by other values. Sometimes it is necessary to replace some or all of the potmeters if the old ones have drifted too much. This mod does require some work to perform but is a relatively subtle modification where a maximum effect is attained without adding extra tubes. The resulting tone is excellent and versatile!

The end result also depends on the quality of the transformers as present in the amp. Usually the transformers in the amp are re-used, which can be a limiting factor, especially in the more modern amps. Better transformers can be fitted ofcourse but that will drastically increase the price of this mod.

Prices from € 500,-.