This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Tuesday, December 16, 2014

Wampler Plexi-Drive

Here's Wampler's Plexi-Drive, another Marshall-in-a-box pedal. The original unit uses a 470µ capacitor for power filtering, which seems like overkill to me. I've replaced that with a 100µ cap that should do the job just fine.

Some build reports on FSB say that the 15k resistors from 9V to the drains of the J201s might need to be tweaked to bias the JFETs correctly (4.5v), so either socket those positions or use trimpots. Also, if the tone control is too dark sounding for your taste, replace that A25k pot with an A500k to brighten things up.


  1. i fitted mine with trimpots for the drains of those j201's, i had breadboarded something like it just before and figured it was very sensitive to bias in order to get good tone out of it, but when you come around the good numbers its awesome. ill try the tone pot swap and might thinker with the bass switch...we can never have enough options can we ? :-p

  2. Hi, I have a 3 pin on/off switch. Is it possible to use it instead of the spst by connecting the middle as SW2 and an outer leg as SW1? Thanks for the great posts. Having fun with some of your layouts.

  3. Hi :)

    First, thanks for your blog, it's amazing !!! :D

    The stock tone control is very useless, i recommend to put a 47nf for the tonality condensator (10nf). It works very very well ;)

  4. I make a tweak i remove the bass switch, and I put 1M Log potentiometer to control the amount of bass, like the original two channels from Plexi, Normal and Bright.

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