Thursday, 30 April 2015

Dallas Fuzz Factory guitar pedal with AC128 germanium transistors

I've recently been learning how to play my guitar.
Not just banging out chords, as I've been doing for over twenty years now, but actually play the thing. With riffs and licks and the like. I got the Griff Hamlin Blues Guitar Unleashed course, and his Five More Easy Blues Solos lessons, and set about learning some guitar leads.

I've had the courses for about 8 months now, and still haven't got round to really spending any time with them -  I'm not much further on than I was when I first tenatively plucked out the opening notes of Ugly Kid Joe's "Everything About You" back in the early 90s.

Someone suggested going to a live jam session - not only to learn from others, but to put myself in a position where I have to learn something new or interesting, so I've something to "show off" on the night. So I attended a couple of Blues Jam Meetups and have played live with a band a couple of times now. At one point I even got in front of the mic and sang a little song


One thing I'm not mad about is bands where the guitarists "compete" over the course of the night, getting louder and louder. But there I was, on stage, with 12 bars to fill with some guitar noise. So I broke out my three guitar licks I knew and played them. And it sounded ok. But what I really needed was an extra little bit of oomph, just for the guitar solo - after that night, I decided that what I needed was a stompbox!

About a million years ago - ok, about two-and-a-half - at BuildBrighton we ran a build-your-own guitar stompbox effect workshop.

It was really well attended and everyone - eventually (some returning the following week) - went away with a working pedal. So we have a design which we know works. But one thing that's always been a bit of a bugbear is how it was constructed using perfboard.


Sure, that's great for the workshop, as it demonstrated the "hack-it-together-yourself" approach we wanted to get across, rather than just a "solder-this-existing-kit-we-made" type of workshop. But it always felt a little bit incomplete. But, just for this project, a PCB just felt right. So we set about designing one...


The schematic is a slightly modified version of the original one, with all of the controls brought out onto the front of the pedal


This design includes pots for
  • stability
  • compression
  • gate
  • drive and
  • volume
The PCB layout was designed so that the pots could be fixed straight to it, and that it would lie at 90 degrees to the "face" of the box, to reduce the amount of space that the actual circuit board took up, inside the box.


Amazingly, after soldering everything (ok, most things) up, it all still fit in the enclosure just right


Here's the final pedal, with all the plugs added, pushbutton fitted and all controls in place.



Maybe we could ask Steve to design us a funky new sticker for the top surface.

The only slight problem we have with this now is that is uses some old-school AC128 germanium PNP transistors - and we haven't got any here to actually test the pedal with! Perhaps Jason will turn up with a pocketful of them at tonight's BuildBrighton Open Evening?