Motivation

I have build my first synthesizer in the late 70’s. And I am playing Shakuhachi for seven years now. Time to bring both worlds together. Here we go.

The aim of this project is to provide Shakuhachi players with the means to control an analogue synthesizer simultaneously with playing the Shakuhachi, without affecting the playability of the flute.

So far it consists of three main modules: the pitch-to-voltage converter, the envelope follower and the “E-Shak”. The pitch-to-voltage converter derives a voltage from the pitch played on the Shakuhachi. This is used primarily to control the pitch of the VCO (which is the initial generator of waves in the synthesizer). The envelope follower provides a voltage which follows the volume of the Shakuhachi, together with gate and trigger signals. These are used mainly in conjunction with the synthesizer’s VCA (which is responsible for the dynamics of the synthesizer’s signal). The “E-Shak” is an exoskeleton attached to the Shakuhachi with crepe tape. It is equipped with an accelerometer with three axes and with three switches. This module provides three control voltages according to the movement of the Shakuhachi, and three additional on/off switches. The usage is only limited by the player’s imagination.

Shakuhachi 2 Synth project: Block diagram

Shakuhachi 2 Synth project: Block diagram

In the block diagram you can see the basic structure of the project. The microphone signal goes to the “Shak 2 Pulse” converter and the envelope follower (ENV). The Shak 2 Pulse converter is a band pass filter followed by a zero crossing detection with adjustable threshold. The output is a pulse train with the same frequency (pitch). This pulse train is converted to a voltage according to the pitch. The output voltage is available in V/Hz and V/Oct format. The envelope follower generates the gate (+5V), the trigger (+5V/20ms) and a voltage following the amplitude of the microphone signal. The “E-Shak” is an exoskeleton equipped with a three axis accelerometer and three touch sensitive switches. With the interface you can adjust the gain and the inclination of the accelerometer signal. It provides three gate signal (+5V) as well.

Specs and Features

Sitelist

Current state

S2S Current state

S2S - Modules

S2S Shak to pulse filter

Shakuhachi 2 pulse filter

Shak 2 Pulse filter

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Current state: Version 1.0.1 published

This is the front end to the pitch 2 voltage converter for my Shakuhachi 2 Synth project. The incoming signal from the microphone is bandpass filtered and a pulse train is derived from the signal.

S2S Pitch to voltage converter

Pitch to Voltage converter

Pitch 2 Voltage converter

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Current state: Version 1.2.0 published.

Here is the pitch 2 voltage converter for my Shakuhachi 2 Synth project. It is based on an article in Electronotes EN#84 p5-p9 from Robert Iodice. It consist of some control logic and a 12bit DA converter. I have found a fault in the control logic and simplified the DA converter. The original only had a V/Hz output, so I added a V/Oct output..

The circuitry takes a pulse train and converts it to a voltage according to the frequency of the pulse train.

The circuit has the advantage of sampling very quickly (only two pulses required) and holding indefinitely.

S2S E-Shack Interface

E-Shack Interface

E-Shack Interface

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Current state: Version 0.9.5 --- Next: Version 1.0.1 To be published

Here is the interface for my "E-Shak". The input comes from an exoskeleton attached to a Shakuhachi. It is connected to the interface with a 10 wire ribbon cable. The exoskeleton is used as addition to the pitch 2 voltage converter and the ENV follower. Inputs are three voltages from a three axis accelerometer (x, y, z) and three touch sensitive switches (Gate 1, 2, 3). The output range foe x, y, z is adjustable in gain and volume. This gives a wide variability in usage. The three gates are 5 V. The state is indicated with LED.

Condensed Version

Envelope Follower

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Current state: Version xxx To be published

tbd

NGF - Modules needed for the S2S patch

Limiter/Compressor

Limiter Compressor

Limiter/Compressor

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Current state: Version 1.1.0 published

To handle the great dynamic range of the Shakuhachi I needed a compressor for my Shakuhachi 2 Synth project. Because a limiter is not that different I added this feature as well. This comes in handy with my Vocoder project also. The structure used here is derived from "Small Signal Audio Design" by Douglas Self p682ff. The audio signal did not flow through a VCA as in many other implementations. Instead the compression or limitation is done by subtracting the audio signal at the output summing node according to the control voltage derived from the audio signal.

Envelope follower

Evelope Follower

Envelope follower

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Current state: Version 1.1.0 published

This envelope follower was first build for my Shakuhachi 2 Synth project. But it is useful for any other input signal which you want to derive a control voltage from. It provides a gate and a trigger signal as well. The envelope follower is used to detect the amplitude variations of the incoming signal and produces a control voltage that resembles the variations in the input signal. The gate and trigger signal is derived from the input signal as well. You can vary the threshold to determine at what minimum signal level the gate goes high and the trigger fires. Gate level is +5V. Trigger level is +5V/1msec.

Microphone Preamplifier

Microphone preamplifier

Microphone Preamplifier

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Current state: Version 1.1.0 published

I needed a microphone preamplifier for my Shakuhachi 2 Synth project. So i build one. The schematic follows the circuitry given in the data sheet of the SSM2019. Nothing fancy. A optional volume indicator is added. I didn't bother with phantom power. I already have a external unit and didn't want to go into the trouble designing something.

Scaled Voltage Reference

Scaled Voltage reference

Scaled Voltage Reference

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Current state: Version 2.0.1 published

This module provides high precision CV outputs in 1V (octaves) and 83,3mV (halves) steps. The 1V output goes from 0 to 8V. The 83,3mV steps goes from -5 to plus 5 steps (halves). This module is thought for all who are missing octave switches in some modules. Especially in VCO. With this module you can switch octaves and halves as well.

DC Mixer

DC Mixer

DC Mixer

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Current state: Version 1.0.1 published

This is an often needed utility module. The mixer comes in handy for mixing CV sources and audio sources as well. This version is DC coupled, so you can use it for AC and DC mixing. There is an inverted output added. You can reverse the DC-CV mix with it or experiment with feedback loops in the audio domain. The added volume indicator us useful for finding the appropriate signal level. The volume indicator is optional. You can leave it out with no problems for the other functions.

Housing I

Housing

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Current state: To be published

tbd

Housing II

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Current state: To be published

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Sitelist

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