RH-101 Synthesizer – Complete

This is the completed version of my SH-101 style synthesizer

 

The synth has a single 3340 voltage controlled oscillator with square, saw and a sub octave that can be all mixed together at different levels. The sub octave uses a 4093 schmitt trigger NAND gate to generate a pulse from the saw wave (we don’t use the square output as this has PWM adjustment and we want our sub to be a 50% square) This pulse goes into a 4013 divider where it is divided down twice (-1 and -2 octave), then there is a rotary switch with 3 options and a diode steered -2 octave with 75% duty cycle.

Once the oscillators have been mixed they go into a 3320 filter, using the virtual ground summing node the filter provides. The final VCA is a 3360.

Modulation

There is a single 3310 envelope generator which uses a re trigger option so the envelope can be re triggered when a new key is pressed.
The envelope output goes to the filter CV via a level pot but also distributes out to the VCA and PWM

VCA: Switch between Gate or Envelope trigger
PWM: LFO1 or Envelope with adjustable level
Filter: Envelope (adjustable), LFO2 (adjustable) and direct CV control with Resonance

The entire synth fits on a small PCB and is controlled with a PIC 16F1516 and a dual MCP4922 DAC (which does the oscillator CV and the key track offset voltage)
It’s a single mono synth with MIDI In, there is no patch storage available, this just gets too expensive and difficult sometimes.

LFOs

There are 2 LFOs, 1 is for the PWM and 2 is for the filter, with and adjustable level. The LFO is square wave only and is generated from the MIDI clock with 3 options:
1: Beat
2: 8th Note
3: 16th Note

Below is a link to the whole repository including:
PCB Files in KiCAD
Software in MPLAB X  (For PIC 16F1516)

https://drive.google.com/drive/folders/1VtsbTb-uA2jX1FQZ5N9y59OMS3xPtcG2

All the downloads are completely free and this project is open source, but please consider donating, there has been alot of time put into the testing and design.

https://www.paypal.me/rhelectronics

Posted in Uncategorised.

Leave a Reply