Buy one here: https://www.tindie.com/products/diysynthjunk/twelvey-12-channel-control-voltage-interface/

Overview

Twelvey provides a compact control voltage interface for one “octave” of musical notes. Twelve voltage divider circuits send distinct voltages through a common output port.

Technical Details

This device contains twelve parallel voltage divider circuits, each providing between +5V and +6V of “control voltage” for a CV-based sound synthesizer. By adding “keys” (e.g., momentary button switches), this circuit will approximate the 1V/Oct implementation common on several analog synthesizer platforms, as follows:

Keys

Input Voltage (V)

Output Voltage (V)

1

9

5.00

2

9

5.09

3

9

5.18

4

9

5.27

5

9

5.36

6

9

5.45

7

9

5.55

8

9

5.64

9

9

5.73

10

9

5.82

11

9

5.91

12

9

6.00


Audio output may or may not equate to a true musical “octave;” this device can be connected to any number of possible synthesizers under any number of possible conditions. The output should, however, constitute twelve distinct voltages, increasing regularly from lowest to highest, which may approximate an octave-like scale.

Rating

Designator

Footprint

LCSC Part Number

40V 3A 550mV @ 3A Schottky Barrier Diodes

D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12

SOD-123FL

C142342

1KΩ Resistor

R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25

R0603

C118155

1.2KΩ Resistor

R14

R0805

C269531

220Ω Resistor

R26

R0603

C203410

100Ω Resistor

R27

R0603

C269683

330Ω Resistor

R28, R29

R0603

C325681

470Ω Resistor

R30, R31

R0402

C325387

560Ω Resistor

R32

R0603

C325729

680Ω Resistor

R33, R34

R0603

C325626

820Ω Resistor

R35, R36

R0603

C325631

30Ω Resistor

R37, R40

R0805

C325808

5.1Ω Resistor

R38

R0805

C325852

9.1Ω Resistor

R39

R0805

C245438

82Ω Resistor

R41, R45

R0805

C325829

68Ω Resistor

R42, R44

R0603

C325751

47Ω Resistor

R43

R1206

C325924


General Usage

To use this device as a CV controller, connect the following:

  1. A power supply
  2. Buttons or switches
  3. An output jack

Additional Options

This design features a space (currently unused) for a built-in dual oscillator based on Texas Instruments’ Dual 2-Input NAND Gate With Schmitt-Trigger Inputs (SN74LVC2G132). Certain locations on the PCB (Ports 1-7, 3G, 7G, and IC SW) are designed to work with this planned feature.