Building a Guitar Fuzz Pedal in a Hammond Octagonal Enclosure
I am a great fan of the Hammond enclosures, not least because they do them in a nice shade of red and in some interesting shapes. Looking at the octagonal one, it occurred to me it would be the ideal enclosure for a guitar fuzz box – specifically one based on the classic “Fuzz Face” made famous by the likes of Jimi Hendrix.
[Picture by Starman1984 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20588329]
I searched the Internet for circuits and was pleasantly surprised by the amount of information out there. The Fuzzface has few components, being a relatively simple two transistor circuit and there is a fair bit of discussion about which transistors give the best sound. The original Fuzz Face was first made in the mid 1960s and used germanium ones.
Typically, germanium transistors produce a slightly less harsh sound as they do not handle higher frequencies as well as their silicon counterparts. The vast majority of transistors manufactured today are silicon as they are easier and cheaper to produce. Germanium transistors can be found on eBay and some specialist web sites, but I decided I would go for the easier and less potentially problematic option — and silicon transistors instead. If I used sockets to mount them I could then swap them out fairly easily and compare the different fuzz sounds.
Having looked at various circuits I decided a stripboard version would suit my skill level and from the information I gleaned I put together a BOM.
- 1 x Gain - linear – (745-6772)
- 1 x Vol – Audio - A500K (692-8639)
- 2 x “chickenhead” potentiometer knobs (022-3742)
- 1 x stereo 6.35mm jack socket (047-7567)
- 1 x mono 6.35mm jack socket (047-8015)
- Foot switch – (846-6739)
- 9V battery connector (048-9021)
- Octagonal Hammond enclosure (756-8761)
- Stripboard (159-5420)
I started by putting together a breadboard version of the circuit and tested it using the bench power supply. My first attempt only worked intermittently and after some attempts to fix that, I decided to start again; this time using the rigid style of jumper wire, since that gives a tidier result and I find it easier to see what is going on. I bent my own small lengths of wire but then remembered I had a box of ready made jumpers in different colours (634-8651) that would have made life even easier!
I started with the 2.2uf capacitor and gradually added the other components and connecting jumper wires. I made sure I had the transistors in the right way round, referring to the data sheet that clearly shows the Emitter, Base and Connector wires.
As I did not have a guitar handy so I found a YouTube video of someone playing the guitar, took the sound from my PC and fed that through the Fuzz Box circuit to one of my 12V speakers. This is how it sounded:
Now I was happy that it worked, it was time to solder a more permanent version together on the stripboard. I had used stripboard previously for the amplifier circuit in the 12V speakers, so the process was not entirely new to me. I cut a piece of board big enough for the small number of components, with a bit extra along one side to add screw holes for fixing. To cut the board I used a steel ruler and a sharp knife to score the board a number of times, before snapping it in a vice. I then finished off the rough edges carefully with a small, fine file.
I then broke the copper tracks in the appropriate places using a stripboard cutter (543-535)
Once that was done I could solder the components in place.
Drilling The Enclosure
I followed the layout of the original Fuzz Face, just adapting it slightly to take account of the octagonal rather than circular case.
I followed my usual process of laser cutting a template from a scrap piece of MDF, drilling the appropriate size holes to accommodate the potentiometers and foot switch in the top, along with the output and input jack sockets in the side.
I secured the circuit board using Velcro (466-2781) so as to avoid drilling holes into the top of the enclosure or having multiple wires between the top and the base.
I trimmed the shaft on the potentiometer that controls the fuzz and fitted a “chicken head” knob on that and the volume for that authentic retro look.
There does not seem to be a great deal of variation in the level of fuzz using these components, so I will try some different transistors to see what difference that makes and may also try swapping out some of the other parts. I also need to try it with a real guitar!
I now have a taste for building effects pedals, so I am looking round for my next project. I know that old school effects were built using point to point soldering and, having tried that in an ongoing valve amplifier project, I am thinking I may try that for the next effects unit.