www.96kHz.org
advanced audio recording
a CV-electronic module for analogue synthesisers
 
MIDI

2

CV


1kHz

Block Diagram


midi to voltage converter with FPGA - Juergen Schuhmacher 2003

This design shows the analog path of the design for one channel: The digital PWM / PDM output of the PLD / FPGA is filtered with a high cut filter to obtain an analogue voltage. A configurable amplifier with an OPAMP apmplifies by ratio 2.5 taking an offset into acount.
Therewith an analoge output between 0,25 and 5,25 V can be achieved, making it possible to tune and calibrate the synthesizer in software.

4 channels can be realised with one single OPAMP of LM324 type. The PLD signal runs at full speed 20MHz and create 10MHz-pulses. In that ways 10.000 pulses resolution are available for the desired 1kHz signal precision.  After filtering this gives an accuracy of 40dB ... 46dB THDN for a typical signal change of 100 Hz ... 500 Hz. PDM is a stage 2 modulator. VHDL-Entry has been done using VHDL Studio


Frequency Table

The subsequent table shows the required voltages to create the music frequencies. The 5V output covers 5 octaves. For the 10V specification a larger scaling with other Opamps had to be selected.

midi to voltage values for analoge synthesizer - Juergen Schuhmacher 2003

Here linear relationship is used only. For a logarithmic control option a larger scaling of the opamp amplification had to be implemented. Standard CV-commands as triggers can be applied any point of time. The circuit has full DC-capability.

Eagle - PCB

The PCB-Design has been done with CadSoft - EAGLE 3.5.

PCB of the midi to voltage electronic


A XC4000 PLD had been used and later moved to a current XC2S200.  .

  
48 kHz
Audio DSP

 

© Sound of L.A. Music Productions 2003