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< 3 Little Pigs > Medium Gain DIY Overdrive pedal project

Postby maz » February 10th, 2020, 2:31 pm

Quick Overview:

    - Type: Medium Gain Overdrive
    - Level of complexity: 2/3
    - Nb of parts: 33
    - Nb of amplification stages: 3
    - Input: NPN Transistor 2N5088
    - Main stage: J201 JFet
    - Output Buffer: 2n7000 Mosfet
    - Clipping: Hard (1N914 diodes)
    - Nb of Potentiometers: 3 - (Drive Tone Level)
    - Schematic tested: Breadboard
    - PCB Layout: Yes
    - PNP transfer: Yes
    - PCB Size: 21 X 12 holes
    - PCB tested: no
    - Veroboard Layout: Yes
    - Veroboard Size: 15 X 21 holes
    - Veroboard tested: no
    - Soundtracks: No

The 3 Little Pigs Overdrive was created because I was missing a tone that would be more "tubey" than the conventionnal overdrive circuits using an Op Amp as the main amplification/clipping stage. The J201 JFet has been selected since they are known to have the higher gain of all but also because they can deliver a sound very close to a 12AX7 tube (ref: Fetzer Valve). The input stage is a typical common emitter adjusted to push the JFet stage by using a 2N5088 NPN transistor, the suggested gain is about 600 hFE, any high gain NPN with a suitable pinout can be used there, just make sure the collector sits around 4.5V at idle, therefore R3 can be adjusted. For the clipping section I tried many combinations of diodes and leds but my ears found 2 symmetrical silicon diodes to sound the best. The tone control has been placed just before a typical output buffer to recover the signal. The Pig Switch connects a 22uF capacitor from the J201 source to ground for a little more grit.

I'm very pleased with all the overdriven tones I can get from this circuit, there's a slight compression that I love when playing some musical styles, R8 can be lowered to get more of it. The Pig SW is nice too and the tone control doesn't affect the volume, the output is unity at the center position of the Level pot. The veroboard will be marked as Verified very soon !

Schematic < Tested on breadboard > :

Image

Image

:pdf: Download the complete pdf project file for direct PnP transfer, layout and schematic.

:txt: Download Bill of Materials in txt format.

The 3 Little Pigs Overdrive built on Veroboard :

Image

Happy DIY !
All together, bigger we can be!
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