Overview

Specification

Iosefka is a hybrid digital analog monophonic synthesizer consisting of the following parts:

Digital audio:

• 2x wavetable oscillators, capable of interpolated morphing waveforms in the X and Y dimension along 256 hand-picked waveforms in a 16x16 layout
• White noise generator
• Sample-rate reduction and Bit-rate reduction effects
• Loopback digital delay fed from VCA output with feedback and adjustable rate from >3 ms to ~683 ms

Analog audio:

• V2140 based analog pole-mixing resonant voltage controlled filter with audio rate frequency modulation selectable between:
  • 2 pole low pass
  • 4 pole low pass
  • 2 pole high pass
  • 2 pole band pass
• LM13700 based voltage controlled amplifier
• External audio input direct into analog section and digital delay

Step sequencer:

• 32 step, 24 PPQ performance step sequencer
• Parameterized sequence generator including step chance, length, octave range, and musical scale
• Controls for swing, direction, clock division, first and last step, probability
• Per step Parameter locks for:
  • Note value
  • Step length
  • Velocity value
  • Step Probability
  • Single audio Parameter
• Per step mutes

Modulation matrix to all audio Parameters:

• 3x ADSR envelope generators (converted to control voltage for analog modules)
• 3x Low frequency oscillators (converted to control voltage for analog modules)
• Velocity control
• Aftertouch control
• Mod Wheel control
• Breath Control
• Pitch Bend Control

MIDI Implementation:

• MIDI RX
  • Note and velocity values
  • Realtime messages: clock tick, start, stop
  • CC messages for all audio Parameters (see implementation chart)
  • Modulation control of velocity, aftertouch, mod-wheel
  • Pitch bend with configurable bend range from 1 to 12 semitones
  • Program change (coming soon)
• MIDI TX
  • Note and velocity values (from keyboard and sequencer)
  • Realtime messages: clock tick, start, stop

Patch storage:

• Store 64 patches of all audio and sequencer Parameters
• Store global MIDI and machine settings

Oscilloscope:

• Oscillator phase locked oscilloscope with four 'time' divisions (sample divisions) between 512 to 128 samples.

Hardware

Hardware components listed in the manual will be referred to by their name as listed below. When hardware components are listed in the manual, they will appear in Bold and Italic

1. OLED Display
2. Data Rotary Encoder - (with switch when pressing down on shaft)
3. Shift switch
4. Play/Stop switch
5. Layer LEDs
6. View switches
7. Page LEDs
8. Key switches
9. Potentiometers
10. Volume knob
11. Output Audio jack
12. External Input Audio Jack
13. Filter tracking tuning trimpot
14. Filter offset trimpot
15. MIDI Output jack
16. MIDI Input jack
17. Power supply jack - (9v DC - Center positive)

Synthesizer Block Diagram