Hello. Another day, another Teensy synthesizer. TSynth is a two oscillator, four note polyphonic synthesizer with a large number of waveforms including user defined, state variable filter, two envelopes, PWM options, LFOs for oscillators and filter, effects, patch saving and recall. I went mad with the Audio Library really and cannot begin to express how fantastic it sounds and the possibilities it opens. The full spec is below and it fully utilises the USB host on the Teensy 3.6. It will receive MIDI via the client USB from a pc (which also provides digital audio appearing as a soundcard), the USB host port (I can connect my controller keyboard directly) and normal 5-pin DIN MIDI.

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Most of the pots, switches, buttons, display and encoder are connected via two 16 channel MUXs, the rest to the Teensy pins directly. It is a mess of wires inside and a PCB would be fantastic. A demo video will follow soon.
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Teensy 3.6 with Audio board - this shows how the USB host port pins were soldered.
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Oscillators
  • Four voice polyphony (last note priority), two oscillators per voice, detunable with +/- 2 octaves range, Sine/Sample & Hold (like tuned noise)/Square/Sawtooth/Ramp/PWM/Var Triangle/User waveforms and level
  • Pulse Width/Var Triangle can be set for each oscillator with PWM by dedicated LFO or from the filter envelope
  • Pink noise with level
  • Dedicated LFO for pitch mod (can be retriggered by note on) , Sine/Triangle/Sawtooth/Ramp/Square/S&H waveforms
  • XOR ‘Ring Mod’ (creates lots of harmonics with certain waveforms)
  • Unison with all eight oscillators detunable from each other
  • +/- 12 semitone pitchbend range
  • Mod wheel controls pitch LFO amount

Filter
  • State variable 12dB filter (SVF) with continuous mix between LP and HP (provides notch filter) and BP
  • Cutoff freq and resonance
  • Cutoff can be modulated by dedicated ADSR envelope, dedicated LFO and key tracking
  • LFO has same waveforms as pitch LFO (can be retriggered by note on) and rate can be set to match MIDI clock (tempo) with variable delay per bar


Amplifier
  • Dedicated ADSR envelope
  • Glide (up to 1 octave range) with variable time
  • Volume for DAC output
  • Effect amount and mix - currently for stereo chorus but could be set up to allow choices in programmer


Programmer
  • 160x80 IPS colour display
  • Encoder with button for data entry, Back button for menu navigation
  • Save and Recall buttons for storing patches, holding Recall initialises the current patch to match the panel controls
  • The programmer makes the synth very flexible with possibilities for changing User waveforms, alternative filters, alternative effects with further parameter settings.



MIDI
  • USB HOST MIDI Class Compliant (direct connection to MIDI controller, no PC needed)
  • USB Client MIDI In from PC
  • MIDI In 5 pin DIN



Audio
  • SGTL5000 Audio Shield 16 bit, 44.1 kHz Stereo out
  • USB Audio in/out—appears as 16 bit, 44.1 kHz audio interface on PC



Hardware
  • Teensy 3.6 with SGTL5000 Audio Shield. Two 4061 multiplexers providing 32 channels from the pots into two ADCs. The rest of the pots and switches use remaining pins on Teensy.
  • Enclosure is laser cut acrylic with etched labels filled with yellow acrylic paint (this technique could be improved with experimentation), end cheeks are 3D printed.