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 9, 2014

Simple Transistor Compressor

FSB member Mictester came up with this design a couple years ago. Utilizes 4 transistors, 1 PNP and 3 NPN, though you could probably use an NPN in place of the PNP. Best to socket and try a few different transistors. The schematic says BC213L for Q1 and BC183L for Q2-4, but any medium gain transistors should work okay (2N2222, 2N2907, 2N3904, 2N3906). I added some of the mods suggested in the FSB thread for higher input impedance and noise reduction.


  1. I made this and worked great. I needed to replace the PNP with an NPN transistor. I even replaced the 1n4148 diodes with 1n4001 and still worked.

  2. Just built it. Hope to make another contribution here. I also used an NPN transistor for Q1. I tried an PNP one without success. The ratio pot functions as a rheostat there. However, when it was turned to the lowest resistance. There was some helicopter noise. So I have to add a resistor in series with the ratio pot. 47 or 100 ohm would be fine.