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.

Monday, September 7, 2015

Mona Lisa Overdrive

Here's a light-medium gain overdrive designed by RNFR from the Apocalypse Audio blog. Here's what he had to say about it:

I thought I would build something that would turn on the guys that were into the lighter side of things- something different than my usual wall of fuzz tones.  With the MLOD, you can get a heavy boost, or a light overdrive reminiscent of vintage microphone preamps.  The fancy thing about this circuit is the lack of coupling caps in the audio path- something usually reserved for mic pres and hifi circuits.  This lends itself to the "transparent",  uncolored sound happening here.  If you encounter any oscillation at the highest gain settings, simply raise the value of the 100 ohm resistor near the gain control to lower the amount of maximum gain. 

Use sockets for the transistors. I'd start with J201s or 2N5457s for Q1 and Q4, and 2N2222 or 2N3904 for Q2 and 2N2907 or 2N3906 for Q3.


  1. Verified.

    The effect is indeed very transparent. Even with the the gain at max, you can get clean sounds by plucking the strings softly. Since the circuit is emulating an over-driven mic preamp, the distortion is dry, crackly, and solid-state sounding. It's more of a specialty studio effect, and needs an already breaking-up tube amp to sound its best.

    The effect doesn't have a lot of volume or headroom. With the Volume pot maxed, I got unity gain at about halfway on the Gain pot. By that point, I got distortion when hitting the strings moderately hard, especially with humbuckers.

    I tried 2N5857, 2N5458 and J113 for the JFETs and 2N3904/2N3906 and 2N5088/2N5087 pairs for the BJTs, and they all seemed to work fine.