Published on Jan 7, 2017 Tho Mai
"For more information & source code see: https://github.com/thomai-d/MonoTon"
"Features
8 instruments (Kick, Hat, Snare, Shaker, Clap, Noise, Sine, Square)
Each instrument has 4 banks a 16 steps each and can be muted
Synthesis using 8bit wavetables
20000Hz sampling rate
Master is filtered through analog high-pass filter (2pole)
Hardware
atmega1284 @ 16MHz using Mighty1284 platform
lots of 74HC595 shift registers (for LEDs)
MCP23S17 port extenders (for buttons)
CD4067 multiplexer (for analog potis)
R2R network for D/A conversion
Some eagle files included
Lessons learned while developing
The analog inputs are quite noisy. De-noising uses quite much cpu.
Don't ever solder this much wires by hand. PCB services are your friend.
Prefer DDS over an R2R ladder.
Open bugs / flaws
Although the output is buffered by an opamp, the sound sounds distorted when using the PC's line in. If I conntect it directly to the speakers, the sound is quite clear."
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