Marshall Plexi

This particular amplifier was initially a '93 Marshall Plexi 1959 MK2 Reissue. The amp sounded pretty good stock but i felt there was room for improvement, so i decided to take action. Ironically, the circuit used on plexi reissues produced in '93 specifically was different than all other reissue models and actually sounded better. However, i still felt the need to make it more authentic.

I replaced the pcb circuit board with a nice hand-made turret board. Like the JTM45, i populated the board with NOS Allen Bradley carbon comp resistors in selected places and Sozo Mustard coupling capacitors (unlike the JTM45 where i used the vintage series caps, in this one i used the regular sozos as i wanted a less smooth sound than the JTM45). I also used F&T filter caps, alpha pots and ultrafast diodes for the bridge rectifier in order to help tighten the bass a bit. Again, special care was taken in the grounding scheme and the lead dress to keep the amp as quiet as possible.

In this amp i added a couple of mods to add variety. The first one is a push-pull pot that engages and disengages the dreaded bright cap of the treble channel. Especially useful when overdrive pedals are involved, it takes the harshness away and can be switched back on when extra sparkle is required. The second one is a push-pull pot that toggles between split and shared cathode for the V1 tube. That is the main difference between a '68 (shared) and a '69 (split) plexi. Tonally, the difference is that a '68 plexi sounds smoother, a little darker and rawer while a '69 sounds tighter, more aggressive and brighter. The switch adds a lot of tonal flexibility. In the following picture you can see both pots pulled.

I also added a post-phase inverter master volume of the LarMar variety to tame the amp - it is one of the loudest amps for guitar and some kind of volume control is required to make the amp usable in this age. This particular design is the most transparent and does its job great. I removed one of the two speaker jacks and placed the pot in its place as i didn't want to drill a hole to the amp.

  

Lastly, i replaced the original dagnall output transformer of this reissue with a great Classictone paper-bobbin plexi output transformer. The output transformer plays a great role in the feel and sound of this amp and the replacement made quite a difference.

Sound Files


Marshall Plexi into Marshall 2061cx w/ Scumback M75/H75
Lead Section: Tokai ES160
Rhythm Section: Rickenbacker 330
Recorded with M-Audio FastTrack C600, AKG Perception 420 & Shure SM57. No post-processing.