Monophonic synthesizer with analog signalpad (VCA1,VCF-24dB,VCA2), MIDI and local control. Build-in 2-octave keyboard, battery and headphone amplifier, can be played and programmed stand-alone. Store/recall function for patches.
Sounds are made using only 20 powerful parameters, no menus. OSC with PWM and waveshaping (dedicated LFO) and a SubOSC that can also modulate. Two Modulators can act as Envelope Generator or LFO (MIDIsync). In LFO mode you can apply patterns for dynamic modulation (sound examples). Parameter keys, encoder and a slider control/program the sounds (or use MIDIcontrollers for every parameter).
Synthesizer block diagram VCF circuit: analog 24dB ladder LPF with Q up to oscillation. At very low Q-settings the filter smoothly changes over into a notch filter. The two VCA's are transistorbased with log control. VCA1 can be used to overdrive the filter, VCA2 does the amplitude envelope.
All building info is/will be available at the bottom of this page.
Do realise that this is not a starter project. MonoVoks4 and PRBSynth1 are a better choice for starters.
The Monoladder1 is made of 2 PCB's: The white frontpanel-PCB with the user-interface and the purple synth-PCB, a compact stand-alone synthesizervoice with MIDI-OSC-VCA1-VCF-VCA2. An Arduino ProMini is on the synth-PCB to make the OSC-waves, modulation, MIDI, read knobs, control LEDs and store patches. The OSC-waves are made by a dedicated hardware timer, used as an oscillator, not interupted by the processor.
No aliasing occurs because waveforms are played using what I call "harmonic sampling". I made up this trick, tuning the sampling clock over one octave to be always at a harmonic of the note being played.
A polyphonic synth could also be made using one synth-PCB per voice.
direct output, no effects, no sequencing, only playing some keys and sometimes using the slider or knob
-PWM, modulator pattern on VCF, second part using slider on VCF
-Using modulators on key and filter, subosc added and Q increased
-2 modulators "on the run", patterned pulse wave, modulated filter
-VCF in special "notch" mode (lowest Q setting) creating a phaser
-Classic sounding filter with LFO random sequence modulating it
-Portamento on OSC (PWM) with LFO square wave on filter
-Putting the filter in overdrive by cranking up VCA1
-Synth brass with a wiggle, then a filtersweep with the encoder knob
-OSC makes PulsePattern waves (PRBS) that change slightly in time
-German disco? (sorry for my poor timing playing the notes)
-OSC switched to noisegenerator with build-in LP/BP/HP/BR filter
-Subosc switched to noise(modulatorcontrolled ), OSC doing PWM
-Percussion using an almost oscillating filter
-OSC has basic wave sequencing mode that is used here
-more OSC switched to noisegenerator, ramping down frequency
-LFO-modulators pulse waveform, used as click, filter distorted
-Yes the filter can oscillate
demo "song1" Here the Monoladder is just playing one continuous note (rhytmic pattern) while filter and subOsc are being modified (no multitracking). The backing string chords are played on a Wavestation synth.
MonoLadder1 synth-PCB-circuit diagram
MonoLadder1 synth-PCB top components placing
MonoLadder1 synth-PCB bottom components placing
MonoLadder1 synth-PCB components info
MonoLadder1 synth-PCB gerber files
link to PCB files on OSHPARK (PCB manufacturer)
MonoLadder1 software, Arduino code, version 2w12
Page "Synthesizer circuits explained" for more info on hardware and software