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.

Wednesday, September 14, 2016

Jen Harmon Booster

Here's a really unique overdrive from the Italian manufacturer Jen from the late 70s. Think Tube Screamer meets Big Muff. It sort of reminds me of a DBA design (only more stable and not as over the top) with a whole mess of transistor stages pushing a BMP style tone stack. Originals used BC318c transistors, but others in the 400-500 hfe range can be used. Here's the schematic for reference.


  1. Hi Pedal Builders! I'm really interested in this pedal. Could you please tell me some advice about the transistor? I would like to use BC549B. Thanks in advance!

    1. If you look at the datasheet of the BC549B the hfe ranges from 240 to 500, but typically around 330. So measure what you have to see if they fall in the 400-500 range described above. But really, just use sockets for the transistors and try different ones out. See what sounds best to you.

  2. How about 2n5089's hfe range around 550?

  3. verified, used 2n5088! Sounds like a Typical Fuzz.