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 even needs to be plugged from the Low input into the High input! Not very user friendly. The Clean (Low) channel doesn’t quite sound a like a true Plexi.

What is the 2 Channel Mod?

The popular Dr.Tube 2 Chan­nel Mod elegantly solves all 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 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.

Which Amps are suited for the 2 Channel Mod?

The old Dutch London City and Power City (and in some cases Super City) amps are very well suited for this mod. We’ve even designed a new front panel for these amps, giving this mod a very professional look. 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.

A very transparant serial FX Loop can also be installed, which ofcourse can be switched in and out with a footswitch.

Prices from € 550,-.