Motivation
This module provides high precision CV outputs in 1V (octaves) and 83,3mV (semitones) steps. The 1V output goes from -5 to +5V. The 83,3mV steps goes from -5 to plus 5 steps (semitones). 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 semitones as well.
Specs and features
- High precision output from -5V to +5V in 1V steps (octaves)
- High precision output in 83,3mV steps, +/- 5 steps (semitones)
- Runs on +/-15V and +/-12V
- Power consumption around 30mA each rail
Implementation
Schematic
Scaled voltage reference: Schematic control board
Scaled voltage reference: Schematic main board
Description:
The precision voltage is derived from the REF02 (IC1). The negative voltage is provided with IC2B. It is crucial to match the resistors in the voltage dividers as good as you can (better than 0.1%). The outputs of the voltage dividers are buffered to avoid loading of the dividers. The resistors around the OpAmps must be matched as well. The one Volt and the 83,3mV steps are added together with IC2A. The four outputs are individually buffered.
Calibration
- Measure the voltage at pin 6 at the REF02. Adjust the voltage with TR_1 to 5.000V
Building hints
- It is crucial to match the resistors in the voltage dividers as good as you can. Better than 0.1% if you can.
Special parts
- None
Download
Scaled voltage reference control board documentation downloadScaled voltage reference control board Gerber files download
Scaled voltage reference main board documentation download
Scaled voltage reference main board Gerber files download
Scaled voltage reference *.fpd file
Scaled voltage reference: Front view
Scaled voltage reference: Populated control PCB
Scaled voltage reference: Populated main PCB
Scaled voltage reference: Halve side view
Scaled voltage reference: Side view
