Project

Project Idea: Potential research project into digital and analog audio synthesizers using VHDL/Verilog

References

Very cool video, definitely recommend watching if you have 15 min to spare: FPGA MIDI Music Synthesizer

Helpful video for terminology: https://www.youtube.com/watch?v=c3udLCvoCC0

Cool article on DIY synth effects: "This tiny $29 computer lets you build DIY synths, pedals and more"

• Uses Electro-Smith Daisy board

• Kickstarter

"A synthesizer is an electronic musical instrument that generates audio signals. Synthesizers generate audio through methods including subtraction synthesis, additive synthesis and frequency modulation synthesis."

Terminology

Oscillators: A circuit that produces a periodic, oscillating electronic signal. In music, an oscillator is a repeating waveform with a fundamental frequency and a peak amplitude, forming the most basic sound output that drives most synthesizers. Can use various types of waveform depending on the desired sound.

Waveforms: Sine, Saw, Square, Triangle or various combinations of these.

Subtraction Synthesis: The source sound is generated and then the final audio is achieved through a series of modifiers that refine the original audio

Additive Synthesis: Combines several wave overtones using algorithms to create a richer and fuller sound

Frequency Modulation (FM) Synthesis: Oscillators are modulated using a frequency source within the audio spectrum. Results are combined using algorithms to create a metallic/robotic type sound.

Polyphonic vs Monophonic: Polyphonic can play multiple notes at the same time, monophonic can not.

Audio Signal: Part of the audio path from the generated audio

Control Signal: Used to control a component via a voltage control signal. This is separate from the audio path.

Three main components used within synthesizer:

• Controller: Uses a voltage control signal to control specific modules.

  • Keyboard, Low Frequency Oscillator (LFO), Envelope Generator

• Source: Main sound source for synthesizer

  • Two popular sources: Oscillator and noise generators

  • Controls within the oscillator section: fine tune, coarse tune, octave switch, waveform selector

• Modifier: Anything that modifies the initial source audio is classified as a modifier

  • Voltage Controlled Filter (VCF) - Listen here for examples

    • Such as High Pass (HPF), Low Pass (LPF), Band Pass (BPF), or Notch Filter (NF)

    • HPF - Higher frequencies pass through filter and lower ones are removed

    • LPF - Lower frequencies pass through filter and higher ones are removed

    • BPF - Removes frequencies above and below the cutoff frequency, only leaving a frequency audible

      • Helpful for isolating certain frequencies

    • NF - Opposite of BPF, Removes frequencies at the specific cutoff frequency and allows higher and lower frequencies to pass through

      • Helpful for removing unwanted frequencies

  • Voltage Controlled Amplifier (VCA)

    • Volume Control - Increase or decrease desired volume output

    • Envelope Shaping - Changes the shape of the sound over time. For example, when you strike a key on a piano, the initial sound is a sharp tone called an attack and the sound that reverberates while the key is depressed is called the decay. Adjusting attack, decay, sustain and release values can significantly alter overall sound.