Friday, 1 May 2015

Fuzz Face guitar effects pedal

After putting our Fuzz Factory guitar pedal on hold - while we wait to get hold of some AC128 germanium PNP transistors - we were keen to make something - anything - that could make a noise.

It's often said that the Fuzz Factory is a Fuzz Face with knobs on. Quite literally.
So while we don't have the PNP transistors we need to complete our Fuzz Factory pedal, we do have some metal can BC109 transistors.

And these transistors are used in an alternative NPN, silicon-transistor based design. Here's a schematic based on one of the many designs available online:



It's a basic twin-NPN design, and uses only a few discrete components (resistors and capacitors mainly, and a couple of potentiometers) so it didn't take long to throw together a PCB for it:



This layout is press-n-peel ready - simply print and transfer onto copper board.
Here's the silkscreen layout, to position the components in the right places (from a top-down view, with the copper traces on the underside of the board)


The PCB has been designed to be not more than 24mm deep, allowing it to fit inside a stompbox enclosure at 90 degrees to the "face" of the box - meaning the potentiometers can be mounted directly onto the PCB (no nasty wires running about the place) but the orientation of the PCB means there's still plenty of room inside for plugs, sockets, pushbuttons and the all important battery.

(this photo showing PCB orientation is actually of the Fuzz Factory, not the simplified Fuzz Face, but demonstrates the principle of fitting a narrow PCB into the box at right-angles)

So while we've got a working effects pedal (see video below) it's going to have to wait a day or two before it can go into it's final housing. It turns out that being a ham-fisted oaf in the workshop can sometimes be a bit of a hindrance. Apparently a hole punch is for marking where to drill a hole in the metal box - not something you should actually punch a hole with! I'll have to lighten my touch on the next box....


Here's a video demonstrating the effect pedal in use:



(I couldn't decide whether to have the fuzz on green-for-go, or have the light green and go red when the fuzz was activated. In the end, I went with green=safe, red=danger - so the LED goes red when the fuzz is active. Look out!)

All in all, quite pleasing for an evening's work. Sorry the write-up's not much; pretty much because I just banged this one out, so I'd at least have one pedal I managed to make (and prove works) myself!