Making sound with digital logic usually calls for a Digital to Analog converter. Building one can be very simple, and the sound quality out of an R-2R Ladder is actually pretty good.
In the last edition of Logic Noise, we built up a (relatively) simple VCO — voltage-controlled oscillator — that had roughly one-volt-per-octave response. I even demonstrated it working mostly in tune with another synth’s keyboard. But what if you don’t have a control-voltage keyboard sitting around or you want to combine all of the logic-based circuits that we’ve been building with other circuits under voltage control? That’s where the digital to analog (DAC) voltage converter comes in.
Continue reading “Logic Noise: Digital to Analog with an R-2R DAC”
As [Jan-Erik] had already built a simple USB connected Digital-to-Analog Converter (DAC), he decided to make the high-end version of it.
The prototype you see in the picture above is based on:
- the PCM2707C from Texas Instruments which takes care of the USB communication and outputs I2S audio data
- the PCM1794A, a 132dB SNR 24-bit 192kHz DAC which receives I2S protocol
- the OPA4134, a high performance audio operational amplifier
The on-board +3.3V and -5V voltages are generated by inductor-less power supplies. As [Jan-Erik] mentions in his write-up, the ‘high-end’ was put between single quotes because the PCB is single sided and uses through hole passive components. The board was designed using Kicad, etched by himself and put in a machined enclosure. All the production files can be downloaded from his website so you may produce it within a day.
Want to take back control of how your digital audio files become sound? One thing you can do is to build your own digital to analog converter. This one is made from discrete components, centered around a resistive ladder. Yes, there are a couple of integrated circuits in there which are used for demultiplexing the incoming signal but the magic happens in that R-2R network. The project is an interesting read and makes a point of looking at the issues raised when trying to precision match resistors. Apparently it can be done with 0.1% components if you have a lot of them and a multimeter that can measure down to seven decimal places.
Linear Technology’s LTC2631A-LZ8 is an 8bit digital to analog converter (DAC) with an I2C interface. This DAC can output 255 different voltages, spaced evenly between 0 and 2.5volts. We previously demonstrated the LTC2640 with a three-wire SPI interface, but this version is controlled with only two signal wires.
Continue reading “Parts: LTC2631A I2C digital to analog converter”