I’ll admit, I’m not an avid guitar player. My instrument of choice has always been percussion. Whether it’s slapping my legs to some rhythm in-between my ears or pounding on a djembe or a doumbek or a bodhrán, that’s my first musical love. Heck, I even have an O.G. Roland electronic drum set still sitting in a box after, I don’t know, 9 or 10 years?
Finishing the job
In many ways, this is a continuation (culmination?) of the Randy Destroys Things from last year, when I tore into the Squier Mini Player.Today, I got a bug up my behind, dug out the old amp board, and literally tore it down to the bare PCB. Or as near as matters.
But it wasn’t all for naught: I spent the day also painstakingly tracing all of the circuits on this board to give you (drumroll) a PDF of the schematic, as well as the KiCAD .SCH file (once I figure a good place to host it).
I know, you don’t like KiCAD. I don’t either. Especially not on the Mac. But that open source feeling really expresses itself pretty strongly in me, and I can’t just walk into the arms of CADSoft and pay money for EAGLE CAD, which in my mind is just as frustrating as KiCAD, only in different ways.
No matter, as the deed is done, and KiCAD is what I used to put this schematic together. Note that I didn’t say PCB. That’s because I don’t plan on replacing this board with an exact replica (at least, not if I can help it). As I said in my post last year, this is likely to be redone with a totally different amplifier board, including using a rechargeable LiPo battery pack, as well as a better amp for both the headphones and speakers.
Paying homage to the past
I will say that if you ever want to really grok a device. Really get to the heart of what makes it work, you should take it all the way apart and work out how it was built. I did that with this guitar amp circuit, and learned a ton about how it functions.
You have to understand that this circuit board is not the entire amp. It plugs into the guitar back and includes the volume potentiometer, the tone pot, the pickups, and the 9 volt battery that supposedly drives it all. And tracing the signal from pickup to either speaker, headphone or out the 1/4″ instrument jack is a study in tidy design. I freely admit, I’m impressed for how much this little bugger does in such a small package.
And by reverse-engineering the schematic from the circuit board, this is now basically available to remix and (hopefully) enhance. It really is a clever little design, which takes into account the multiple trips that the signal takes onto and off of the board from pickup to tone control to volume to amplifier to speaker.
At any rate, now that it’s all torn apart, it’s time to rebuild it. Since a year has passed, I am now working on refitting a 3D printer, which will help with the missing panels on the guitar so it can be restored to a fully-functioning instrument rather than a glossy black paperweight.
If you want to have a look at the PDF I made of the schematic, it’s right here for you. I’ll figure out the KiCAD file and host it somewhere suitable in the near future. Stay tuned!