One of Steggo's First Layouts - the Kosmoceratops Envelope Filter!

For the first couple of years building pedals, I was content to mostly just buy professionally produced circuit boards, populate them, and enjoy the awesome tone. However, as time has gone by, I wanted to start learning how to take that next step from schematic to layout. I'd gotten good at reading a schematic and could breadboard, but most of the available programs for actually turning the schematic into a set of Gerber files for a manufactured PCB (Eagle, Kicad, etc.) weren't not intuitive, expensive, or both! A few weeks ago a came across a video by the Tone Geek on how to lay out your own PCB using EasyEDA, so I figured I'd give it a try. Let's just say it's sent me down an amazing rabbit hole and opened up a lot of new possibilities because I'd finally found a layout program that was intuitive and cheap (read free). 

For one of my first layouts (yes, you read that right - it doesn't make sense to just order one set of boards from JLCPCB because of the high shipping costs), I decided to revisit a circuit I'd tried to lay out by hand the year before (unsuccessfully as I really just ran out of time). There was a "PCB layout challenge" on the PedalPCB forum you could enter where everyone was encouraged to submit their own design based on a standard schematic. This time around it was an envelope filter / auto-wah designed by "Chuck D. Bones" of Celestial Engineering. It was based on the Dr. Q envelope filter but whereas that design (at least in its earliest incarnations) only had a single Range control, the new design includes top-mounted Sensitivity and Attack controls. 

With the new program in hand, I first entered the provided schematic which was then converted into a raw PCB. As with any layout program, you actually have to position all of the components and add the wiring yourself, but it does let you set up the board size and position all of the pads for hook-up wiring where it makes the most sense. Another nice feature of the program is you can add images and fonts to the program, which can then be used on the silkscreen on the PCB itself. I was therefore able to bring over the Steggo logo, and print the name of the board on the PCB in on of my preferred "Steggo" fonts. I was also able to use the right font for "Celestial Engineering." I also like to add Easter eggs on the board (such as "layout by Steggi" - Steggo Studios resident tech expert dinosaur, and the "...because who doesn't love dinosaurs?" tag line). Once the board was laid out, I ordered a few and got cracking!

Despite this being a prototype build (above), I went ahead and used my normal mix of components as I honestly don't have a ready supply of less expensive resistors and capacitors handy (the bare board at the start of the blog entry is my second build). The resistors are all 1% metal film (Yageo). The film capacitors are a mix of WIMA and KEMET - generally with 5% or occasionally 10% tolerance. The electrolytic capacitors are all Nichicon. I'd accidentally ended up with some fairly large footprint capacitors from Mouser, so I decided some of my own layouts could be set up to use them comfortably. All of the transistors and ICs are new production from Mouser as well. 

One nice thing about this layout (which wasn't my first), was I'd figured out how to properly space the pads for audio in, power, ground, and audio out to where I could run ribbon cable between the PCB and daughter board like I generally do on all of my PedalPCB (and many other commercially sourced) boards. I was also able to set up the +9V in and enough ground pads at the top of the board so I could connect all of the jacks to the top of the PCB - making for a neat and clean interior. As with all of my builds, the jack connections are insulated with heat shrink tubing.

Once the pedal was together, I ran the initial test and not only did it fire up perfectly, but it's a really fun little envelope filter. Compared to the other envelope filter I've built, a clone of the Mu-Tron III, it has advantages and disadvantages. It's a lot more compact and simpler to operate than the Mu-Tron III, but it also doesn't have the staggering array of options the Mu-Tron does either. It's all really going to depend on what you need at the time!

For the enclosure I wanted to do something fun and I had to come up with a dinosaur that was as "out there" as an envelope filter - so meet the Kosmoceratops! According to Wikipedia: 

Kosmoceratops is a genus of ceratopsid dinosaur that lived in North America about 76–75.9 million years ago during the Late Cretaceous period. Specimens were discovered in Utah in the Kaiparowits Formation of the Grand Staircase–Escalante National Monument in 2006 and 2007, including an adult skull and postcranial skeleton and partial subadults. In 2010, the adult was made the holotype of the new genus and species Kosmoceratops richardsoni; the generic name means "ornate horned face", and the specific name honors Scott Richardson, who found the specimens. The find was part of a spate of ceratopsian discoveries in the early 21st century, and Kosmoceratops was considered significant due to its elaborate skull ornamentation.

I ended up snagging a really cool Kosmoceratops from Adobe Stock and editing it a bit in photoshop. I then use my "Greek theme" that I had used previously on the Monoclonius. Of course, I decided to go with blue trim rather than the reddish I'd used before, so I found a decent color in the art history palette on Illustrator.

This was an incredibly fun process from beginning to end. It was amazingly satisfying to start out with a schematic, take it through layout, board production, then populating the board and finishing a complete pedal design. Given it's compact size, I'm likely going to let it start living on the pedal board as it is plenty of envelop filter for anything I'd want to do most of the time - and if I need that extra bit of insanity, I can always pull out the Mu-Tron III clone if the situation calls for it!