SK-Synth is a substractive synthesizer implemented in a FPGA.


  • Two oscillators with waveforms loadable from flash memory
  • 12dB/octave low pass filter
  • LFO that can be modulate the filter, amplitude or pitch. Possible waveforms are: sawtooth, square and triangle.
  • Filter and amplitude envelope
  • Portamento
  • Legato
  • MIDI-interface
  • Drumpatch with samples in flash memory


The development hardware that have been used is a Spartan-3a development board from Avnet and a breakoutboard with I2S audio and MIDI interface


In addition to the FPGA synthesizer itself, an control application have been written in Qt.

The control application allows modification of the synthesizers parameters.
All parameters are controllable via MIDI control change messages, so it is not mandatory to use the
control application to control the synth.

The synthesizer VHDL source and the control application can be obtained here: