Learning to use the EasyEDA tool has opened up a lot of new opportunities for laying out unusual or unique designs. Recently there was a post on PedalPCB's Chuck's Boneyard detailing an update to an older Apocalypse Audio design. It looked interesting, so I decided to go ahead and test it out and all I can say is "Wow!" It is an amazing overdrive with a really strong and tight low-end.
The layout itself is fairly simple as there aren't too many components. There's only 12 resistors and 8 capacitors on the main board. Throw in a polarity protection diode, LDR, and three transistors and the part count comes out to a modest 25. Two of the transistors aren't particularly exotic - but Chuck's layout did use a NOS ex-Soviet P28 germanium transistor. I happened to have a supply of these I picked up from a friend in Ukraine so I went with it. It sounds great, and looks cool too!
Any time I lay out a board, I try to include a few (or more than a few) Easter Eggs on the board. I found a Silvisaurus icon which is on the front and is repeated on the back of the PCB as well. For this board I'm using the PedalPCB offboard wiring convention with the power connections at the top of the board as well as ground pads for the audio jacks. The daughter board connections are set up for standard ribbon cable and work with my 3PDT daughter boards. The CLR and LED are on the daughter board (and the daughter board has the option for a brightness trimmer - which I didn't use on this build).
As with most of my builds, I'm using Switchcraft 111X 1/4" audio jacks and a Lumberg 2.1mm DC jack. I'm not using a battery on this build, though there may have been room. Per my normal practice, I'm using heat shrink insulation on all of the jack connections. Everything fits quite neatly into the enclosure.
Chuck called his version of this circuit the "Mona Lisa Simpson Overdrive" - I honestly didn't have a great dinosaur that would work with that, so I decided to go with a fun Ankylosaur, the Silvisaurus. According to Wikipedia:
"Silvisaurus, from the Latin silva "woodland" and Greek sauros "lizard", is a nodosaurid ankylosaur from the Early to Late Cretaceous period. It is the only known dinosaur species found in Kansas and was designated the official state land fossil in 2023."
The awesome dinosaur art is one again done by my Ukrainian friend Kate (@estelkatrin on Instagram). The rest of the enclosure is done in the Greek style I've used for a few other original designs or modifications from the Boneyard.
The pedal itself sounds great paired up with my Katana, but I haven't gotten a chance to run it through the Vox or Marshall yet. I figure that it will sound even better once I get it running through those monsters!
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