Things went all fuzzy

Buoyed by the success of last month's "Chafer Drive", I've been busy drawing up layouts for a few more small effects that I want to build, and first up is a tribute to the "Shin Ei Companion Fuzz FY-2". This was a Japanese fuzz pedal made in the 1970's and is generally well-regarded in the DIY effects community for it's classic fuzz tones.

The original came in a large wedge shaped box, but my plan was to squeeze it into a Hammond 1590A just as I did with the "Chafer Drive". This was undoubtedly going to be more challenging, since (a) the circuit is larger, and (b) it has two control knobs as opposed to one. I had some standard 25 x 9 stripboard which I thought would be ideal for this purpose, so I challenged myself to layout the circuit with that in mind.

The original circuit use some obscure 2SC536 transistors (Hfe 160-560) that were no longer manufactured,  but I had a whole bunch of 2SC1685 (Hfe 160-460) transistors that I had pulled out of an old hi-fi amplifier and which looked close enough specification-wise, so I decided to use these.

First up I breadboarded the circuit, and of naturally there was no sound. I checked my transistor pinouts, and sure enough, I had them the wrong way around!  (note-to-self always double-check this). Once I switched them around though it worked like a dream first time, so I spent an hour pretending I was a 1970's guitar hero.

I wasn't totally satisfied though. Although the fuzz control (basically a tone control), gave a nice range of sounds, the volume control was pretty much useless as the effect barely managed unity gain with the it maxed out. So I decided to try to add a boost stage to the output section. I figured a low-part-count transparent boost based on the oft-used EHX LPB-1 would do the trick.

Where I had got the idea that a 25 x 9 strip board would fit, I do not know. Width-wise, there is plenty to spare (12 strips would be OK) but length-wise it snagged on the DC adapter, and was a couple of columns too long at least so I had to shorten the board, which was not a major problem as I had some space to spare. However, the addition of the boost section meant I needed to take the wires out of the middle of the board rather than at the ends which is not ideal really.

My redrawn circuit now looked like this.

schematic

My final strip board layout looked like this

stripboard layout (blue=strips, red=jumpers, holes=cuts)

Next I got to work on the box. The pots I had were slightly smaller (but cheaper and nastier) than the de-facto standard Alpha 16mm ones, and it looked like I could get two of them side by side with some careful drilling, however, I couldn't afford to be out by much more than 1mm, and it was incredibly difficult to be that accurate even using templates and a centre punch. In the end, I had to file the pots slightly to to make up for my inaccuracies. If I was to do it again, I would not try to use 16mm pots side-by-side, and would either offset them (which wouldn't look as good) or use 9mm pots instead.

pots filed-to-fit

Still, it came out OK in the end, and so to the board. First I make the cuts, and use my multimeter to check for continuity (or lack-of) to make sure the cuts are good.

board with cuts made

Next up, the jumpers followed by the low profile parts. I use blu-tac to hold things in place whilst I solder.

resistors and jumpers in place

Then the box type capacitors and followed by the remains capacitors and finally the transistors. I'm not so happy about soldering the transistors because it's easy to damage them with heat, but there is not much choice in these small-box builds as space is really tight.

all components in place

Then I tested to make sure everything was working OK, which it was (once I had grounded it properly).

Finally, boxing it up. I hate this part at the moment. I always seem to have some problems, and sure enough I did, mainly due to bad soldering on the switch, but I got there in the end.

almost done!

It's a tight fit though. I guess I'll improve with experience.

gut-shot

I thought it sounded great on the breadboard into my Micro Marshall, bur when I plugged it into my 15 watt practice amp, it didn't sound as good for some reason, but I'm just going to put it down to experience.

Finally, here it is alongside some commercial pedals, apologies for the blurred picture .

Things I learned/could have done better

1. Keep the board to 22x12 (max). Space at the sides can be useful for routing wires, so 12 may be a bit wide.
2. Input and output connections at the switch end of the board, also a ground if possible.
3. Pot connections at the other end of the board.
4. Use 9mm pots if two or more controls are needed
5. Allow a bit more space between input an output jacks. There is no need to have them too close together unless multiple pots are in the way.
6. Use a DC jack that requires a smaller hole (these do exist) and move it nearer the top of the box (towards the pots), this would allow 25 column boards.