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.

Thursday, February 19, 2015

Jen HF Modulator

Jen was an Italian electronics company that produced a lot of OEM stuff for other companies (Vox, Gretsch, etc.) as well as marketing their own line of effects. For instance, the HF Modulator was the same effect as the Gretsch Playboy.

This effect is a ring modulator and sounds fantastic with a fuzz pushing it. The original unit used 2N5172 transistors (which have BCE pinout), but I've laid this out for more common 2N3904 or 2N5088 transistors (that have CBE pinout). I've also added pulldown resistors, polarity protection, and power filtering.

Here's the schematic if anyone needs it. Most of the ones online have the tone section wrong.


  1. Replies
    1. Not yet that I know of, but it should be fine. Give it a shot!

  2. On the PCB layout the capacitor across B C on Q1 is marked 2.2nf and on the schematic below it is marked 220pf. Swapping out for the 220pf reduced volume drop.