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MIDI to Voltage with Discrete DAC

After my implementation of an SPI controlled DAC i was searching for an 14+ Bit Multiplying DAC. There were some from Linear but not available for an good price.
So here is my try to build an DAC in CS Style. (YM26600). This DAC creates an voltage output for each semitone. For the octaves there is an similar circuit with 6 switches (nit built yet).

For the first tests I started with 12 selected standard 100 Ohms Resistors. The 28.94k resistors are a combination of an 27k  and a 25 turn 5k trimpot. I trimmed the pots as calculated in the simulation and it and the voltages where spot on. The switches are cheap CD4066s. To control them from my Arduino board i build the TTL to CMOS converters.

Here is a picture of the Digital Board with output Buffers an TTL to CMOS converter.

Digi Board Web

 

This is the Resistor Network.

Resistor Network

This is the output Voltega  for the Note B with a 4V Octave input voltage.

Voltage Output B web

Here is the Schematic:

Discret DAC Schematic

UPDATE 24.11.2013

I finished the Wiring to the DAC Board and the Arduino

.ARDUINO DAC Interface _web

Interface ResistorNet _web

Here a picture of the whole Setup

Discreete DAC _web

 

I wrote a little programm to test the whole circuit. It creates voltage steps in halftones.

Stepped Out Voltage _web

 

UPDATE 01.12.2013

Now i have built the Octave DAC. Schematic and coding will follow soon.

Here a short Video.

UPDATE 02.12.2013

Source Code here

MidiToVoltage as .txt File

or  on sourceforge.net

https://sourceforge.net/projects/miditovoltage/

UPDATE 15.12.2013

Added first polyphonic code

Midi to Voltage poly 1.05 as .txt File

This picture shows the multiplexed analog Voltage output. I am not sure with the timing for the following S/H stages. I think is code is not the best but it works.

octave steps2_web

 

UPDATE 27.04.2014

Made PCB Layout in KiCad and thanks to the members of the mikrocontroller.net Forum for their help.http://www.mikrocontroller.net/topic/331468#new

Here is my last version:

Discrete DAC Board v6

will do some changes and will make one next weekend.

It is a single sided PCB. I will upload the final Version incl. KiCAD files if it all works fine.

Here the Schematic:Discrete DAC Schematic

 

Next Steps:

  • Connection to the Arduino Board
  • Building a Gate Out Circuit
  • Writing the Basic Midi to Voltage code
  • Building an S/H circuit

 

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