Components - wrightflyer/Synth GitHub Wiki
To start out I bought a few bits and pieces..
This £20 marvel, Teensy 4.0, is a 600MHz computer. I still find this utterly incredible. I remember when IBM PCs were 4.77MHz !! This is 125 times as fast and is about as big as two large postage stamps...
To accompany the Teensy I also got the Audio Adapter..
As the pictures maybe already show I got a bunch of header pins to solder to the boards. I wanted to make them "Stackable" so waited a couple of days to get hold of some stackable headers which really are worth getting..
While I could win awards for exactly how piss poor my soldering is I eventually ended up with a sandwich... (and it only worked!!)...
BTW one "trick" I came across when researching this was that to make sure pins are parallel you can mount the pins you are about to solder into a breadboard, put the little board on top then solder it...
The next idea I had was that it would be great to have an LCD display for the user interface of the synth. I wanted it big but "portable" so these £5-£10 320x240 displays you can get from eBay looked great. They even have a touch interface on the front that could, optionally, be used to interact with the synth (imagine "drawing" ADSR curves for example!). So I ordered one but because I was itching to get started, rather than waiting for a delivery from China/Hong Kong I ordered a Prime next day delivery from Amazon at twice the price (£10)...
I spent an entire weekend trying to get that to work but simply failed. What's more, while it's true it did say it in the Amazon description, I failed to spot that this didn't have the touch interface fitted. As a back up I also ordered two £5 displays from China thinking they'd take weeks to get here. They only took 10 days in fact so arrived shortly after my first experiments with the first display. I plugged one into the same wiring and it worked immediately. While this photo is very fuzzy it shows the very first output I managed to get from my prototype Synth sketch...
After that I started to try to make some more "synth like" displays which was particularly easy using the ILI9341_t3 library which is closely related to Adafruit_GFX...
The quality of this screen has to be seen to be believed (and this is even though there's a touch interface on top!)..
Other components I ordered, some "just in case", included tact switches (180 of the things!) partly with the idea of building a piano keyboard with these..
Also a bunch of potentiometers to make a "bank of knobs" for adjusting things like oscillators, ADSR, LFOs etc...
But actually I much prefer the idea of "encoders" (as they can be "soft assigned" to various tasks and don't hold a setting (that is in the software) so I got 8 of these and some really nice black aluminium knobs to go on them..
A possibly even whackier idea (though I later discovered the Akai MPK already does this) was to replace the usual pitch and modulation sliders/controls with a dual axis joystick (like a PS4 controller joystick) so I bought a bag full for half nothing...
A few more things I got were stuff like connector wires, some RGB LEDs (every piece of electronics needs an LED to flash!!) and I had followed Dave's videos about making a MIDI-In using an 6N138 opto isolator but in the end I just got a ready-made board so I could connect a 5pin DIN MIDI keyboard to my synth to control it (maybe from a "controller keyboard") but in the end there are so many ways to "feed" input into the things this may not be necessary...
Now I'm not sure if I can actually make any use of this but for £6 (yup just six pounds) on ebay I got this brand new item:
It irritates our cat Amelia so I probably can't play it but I have opened it up to see if I can simply re-use the keyboard plastics from it. There is a wide ribbon cable across from the keyboard part to the main PCB so I may be able to "buzz out the matrix" and hack into it there. But on the other hand the PCB with the actual keyboard buttons is only held against the keys by mounts moulded into the plastic so I don't think it can be fully extracted to be used separately. So I may look at alternatives for creating a keyboard. One idea is to pull a part one of two Akai SynthStation 25's I have...
(stock photo!)
As many of the "mini boards" I had already got have mounting holes and as I planned to mount everything together on some kind of "back board" I got a set of "mounting pillars"...
Another recent purchase was a job lot of 16 channel multiplexers (CD74HC4067 pre-mounted on boards) that would allow the connection of a number of encoders/joysticks to just a handful of pins on Teensy:
Finally (for now!). To be able to use either the laptop or even a tablet as a MIDI source but without involving USB (so it plugs into the 5 pin DIN MIDI board attached to Teensy) I got a £4 USB-MIDI interface from ebay that so far seems to work very nicely..
In order to let the synth connect wirelessly to my main Sony HT-XT1 sound system and also my Sony WH-CH700N headphones I used the fact that Amazon where having a "Prime Day" to pick this Bluetooth transmitter up for a bargain price:
It's surprisingly small (the jack in the picture is a 3.5mm stereo jack to give an idea of scale) but it works wonderfully and allows the Teensy Audio adapter to connect to a powerful sound system. So while I have used a wired connection to a Logitech Mini Boombox previously this allows for the kind of deep sound system the output deserves. I can also use it to connect to non-Bluetooth devices like my old Ymaha SY-35 synthesizer which will allow me to play that through the sound system too. (I got a 3.5mm to 1/4" jack adapter on Prime Day too).
Perhaps my best buy so far is a bargain I got in a £40 eBay auction - an Alesis QX25...
This is a nice size when working alongside the other bits and pieces and most useful of all are the 8 encoder knobs and the assignable slider which can be used to deliver 9 of the most important synth controlling CCs. Most important of all is that unlike all the modern day usbMIDI interfaced keyboard controllers that are available this has the good old fashioned 5 pin MIDI DIN output plug that can either plug straight into the MIDI interfaced attached to Teensy or it can go into the USB interface above, through a program like Ctrlr that adds control changes to the data then back out to the synth.