Moka Pot Fuzz [Harmonic Percolator with Octave Up]

[Aleph Null]

This is my highly tweakable take on the Harmonic Percolator. I've added a modified Push-Me-Pull-You in series for octave fuzz goodness.



Water slide decal on bare aluminum for the graphics. I wanted the metallic look of a Moka Pot.



I used my standard I/O and bypass layout.



A mosfet boost feeds the fuzz section to allow for more saturation. This is especially important as I decided to leave out clipping diodes. They just seemed to mask the character of the fuzz. The Lows control is pre-fuzz. From fully clockwise to noon, it tightens up the fuzz response. Below noon it noticeably attenuates low-end content. The Gain control is just a volume control for the boost output, which feeds the Harmonic Percolator section. I arrived at the values here after much experimentation, trying to get as much tonal variation as possible. The Highs control uses negative feedback to attenuate treble in the Q2 gain stage. Placing it here effectively cuts high-end content without masking the character of the fuzz. Clang sets the bias of Q3 (which in turn effects the bias of Q2). This goes from smooth saturation when counterclockwise (think Albini values), up through the spitty ripping-velcro type sounds the percolator is known for, and into farty misbiased octave down sounds as you move clockwise. Lastly, Octave blends in a separate octave up circuit, which is based on Tim Escobedo's Push Me Pull You, and is optimized to compliment the fuzz. As this sub-circuit comes after the boost and percolator sections, it is sensitive to the other controls.

I'm pleased wth this design. It gets all the sounds I'd want from a Harmonic Percolator while remaining farily ugly proof (for a fuzz).

Here's a demo:

As always, I have extra PCBs. If anyone is interested in building one, DM me.

[jessenator]

Stellar as always! Even if the box is too capacious  

[Aleph Null]

One of these days I'm gonna put a moseft boost in a 1590XX just to spite you! 

[gordo]

Superb!  I love the Velcro fuzz stuff but your lower gain stuff, like what you did with the Peacock, is killer too.

[jessenator]

One of these days I'm gonna put a moseft boost in a 1590XX just to spite you! 

[Aleph Null]

But I'll use all SMD inside. 😈

[jessenator]

[NorthCoast]

Very nice!

I noticed that you changed Q2 from Ge to Si, did you try both?


Happy Thanksgiving everyone!

[Aleph Null]

I noticed that you changed Q2 from Ge to Si, did you try both?

I didn't test a Germanium transistor; I generally avoid them as they are both more expensive and less reliable than silicon. The mosfet boost at the front softens things in a similar fashion anyway.

[Aleph Null]

I couldn't bring myself to do SMD, but I was inspired to make a one knob, mosfet overdive!

You cannot view this attachment.