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, September 5, 2017

Valve Wizard Engineer's Thumb

A little blog update: You may have noticed there wasn't a post yesterday and that there is one today. Why on a Tuesday and not a Monday? Some big-ish changes are coming to the site in the near future, which (along with a bunch of other small things) is taking up a lot of my free time. So don't freak out. I'm still here. Layouts are still coming. Just not quite as frequently (2 a week instead of 3). Now that that's out of the way...

Here's the 5-knob version of the Engineer's Thumb compressor. Been meaning to do this one for a while and decided to do it in Eagle. It's generally considered a Dyna-Comp/Ross Comp killer, and uses one side of an LM13700 chip in place of the old CA3080. This one will fit in a 125B with all 5 pots board mounted. The Bright switch is off board, but that's just 2 wires. If you don't feel like etching, you can get a board fabricated off OshPark. Original info on the circuit by the designer can be found here.

Build doc here with schematic, BOM, and drilling template.


  1. Thank you so much (this phrase is very weak !)

  2. I'm interested to know how this turns out for people, I did not have a very good time with this circuit (two knob)

  3. Verified. Since I wanted to make signal paths bolder rather than ground, re-made a pcb by hand drawing based on the above PCB layout. Works very well. Thank you for great layouts!

  4. Could we get a layout that uses a ca3080?. If i were to build this, could I ommit pots that I don't plan on using?

  5. Stunning!!! Threshold, Ratio, Attack, Release, & Level !!!
    What more could you ask for?
    Look anywhere & everywhere and you won't find anything nearly as precision as this. This is truly remarkable.
    To have a compressor with these features and obvious potential quality available to the DIY community is simply phenomenal! I personally have been searching for several years for a compressor that I could build that has this kind of precision and quality. Now I've found it. Thank you so much!!

    To Jose & Kevin:
    There are lot's of simpler DIY Compressor circuits available here & elsewhere. Just click on the Compressor link under the "Type" heading above & to the left. You will find several very fine compressors that are not nearly as complicated.

    As for me I can't wait for my boards to get here from OSH Park!

    Thank you again! You guys Rawk! And for free ?!?!

    Will Kenworthy

  6. Yesterday I built it, in guiatrra it works very well, today I try it with bass. I could prove that the release to the maximum distorts noticeably.
    Excellent project, thank you!

    1. Hello, I also finish it and the release control when I take it to the maximum also saturates a lot, and also happens to me but a little less with the control of the threshold, could you solve it?

  7. Yo, is it just me or is that ratio pot reversed?

  8. Can I use lm13600 instead of using the lm13700?

  9. Any chance of a perf board version?

  10. Salve, complimenti per il tuo grande lavoro!
    Quali modifiche per adattarlo meglio al Basso ?
    Grazie in anticipo.

    Hi, congratulations for your great work!
    Which changes to better adapt it to the Bass?
    Thanks in advance.

    1. From my understanding it works fine on bass as is.

  11. Hello, after having finished the scheme it seems to work correctly, but I have a problem with the release pot, when I put it to the maximum the sound is distorted or saturated. Does anyone know what the cause may be?