I lived in Beijing when I first started doing DIY electronics, and that was where I first messed around with the Fat Gett. I now live in New York which is where the magic happened. So let’s get on to the birth of the real Fat Gett.
I’ve always loved octave(1), and whilst searching for the Boss OC2 schematic I somehow ended up stumbling across the schematic for the Midfi Electronics Random Number Generator (RNG for short). It seemed like a fun little circuit, and cos it was Midfi Electronics I knew it was going to do something great, seriously if you don’t know about them, check out all their stuff. I checked out the vid and thought yeah why not!? Here’s the schematic I found.
So I breadboarded one and experimented to massive amounts of success related joy. I’ve graduated to the stage where most (some) things (sometimes) work first time (or second time), and experiments actually yield results, which is of course entirely down to persistence, rather than a strong skill set.
When I heard some glitchy sub octave coming through I had an idea. I decided that I wanted to get this running alongside a Muff style fuzz.
As I’ve already discussed, I started with Black Russian values, took out the second clipping stage and tweaked a couple of other bits. So with that on the breadboard, I decided the first thing to try would be to take an out from after the gain knob, which sounded nice and lovely, as you can imagine, it juiced up the circuit right proper. The logic behind putting them in parallel was so I could blend the signals at the end. This was also why I took the out from after the gain pot, so they’d be roughly in balance regardless of the setting.
Next I just tried poking resistors, caps and diodes anywhere I could find holes in the breadboard, but alas everything I tried either had no effect or made it worse. Until! I used a 47n cap and just jammed it between a couple of the transistors and lo and behold, it started to produce a sub octave that whilst being glitchy and messy, still managed to track pretty well, It gave the Fat Gett the bloat it deserved. I sat there playing through my creation with glee for about half an hour, massive grin on my face trying to play pigs pigs pigs pigs pigs pigs pigs riffs that I couldn’t remember and never learnt. After cleaning up the glee, I got back on with it.
As I was playing I started to get the feeling that this could actually be a pedal that I could put out. Remembering that I once accidentally ordered five hundred 2N3904s instead of 50, I thought it might be a good idea if I could switch out the 2n2222 and 2n4401 for 2N3904s. I went to alldatasheet.com to check the pinout and away I went.
Armed with a shaky knowledge of fuzzes and input impedances I thought it might be a good idea to put a 1M pot in series with the signal before it hit the RNG. This, I felt, allowed me to tune the circuit, and it also seemed to make it respond better with its suboctave. When I was playing I noticed that the octave effect only worked lower down the neck. When I took that magic 47n cap out that sub octave shifted up the neck, so what I did was put another RNG in parallel with the first one! Genius! One with the magic cap, one without. I also put the 1M pot in front of this circuit. I came to realise that both circuits worked well when the pots were at their largest resistance, so I just swapped them out for 1M resistors. I tried larger values but they didn’t work as well. I have the original circuit on a footswitch, and there will be a second footswitch to add ‘bloat’ which is the glitchy sub octave from the two RNGs in parallel.
Anyway, here it is:
So there we have it! My first proper design, yeah don’t burst my bubble, I realise it’s cobbled together from two existing circuits, but it sounds pretty boss, so I’m happy with it.
(1) I’ll go into this further with the Rotund Robot, these two projects are linked spiritually.