The SCCC Project (4)

In this installment we will look at how to output analogue signals with the help of sigma-delta DACs (digital-to-analogue converters) and interrupts.

A PWM signal requires just a single digital output on an IC and so it is hardly surprising that these days the digital I/O pins of microcontrollers often come with extensive PWM capabilities. However, there are also downsides: for example, DACs are faster and more accurate. But now an IC is available that offers a simple upgrade to a PWM-based design.

Taking full advantage of the Raspberry Pi’s open architecture, you can customise and program the NanoSound HiFi DAC. With the Volumio software or any other player software and the Infrared Remote Control, NanoSound gives you the best audio performance and experience you can expect from such an audio player.

I wrote previously that it is hard to pass the EXIT / AUSGANG gates at the embedded world trade show in Nuremberg and not have a few demo or dev kits in your sponsored rucksack. That’s why the show is a must-attend for serious electronicists of all ages. I consider myself one but this year I was unable to attend the show and what do you think, I still I received a kit — it simply arrived in the mail a few days later. It is the Otii Arc Demo kit from IoT developers Qoitech in Sweden hence the polar bear on the box. On the Arc box proper I saw “Sony Belgium” printed.

To the delight of many, the previous issue of Elektor had a high-quality network audio player based on the Raspberry Pi/Volumio combination, which however was not provided with a 'real' volume control. Although it is possible to control the volume via Volumio (what’s in a name), but this method seriously affects the high-end characteristics of the DAC for the worse. That is why we now describe a volume control especially developed for the network audio player.

Small single-board computers like the Raspberry Pi are ideal for use as small stand-alone network audio players. With Volumio and other specialized Linux distributions, putting together an audio player is remarkably easy. And as Elektor staff member Ton Giesberts shows in this article, you can also use this approach to build a high-end audio player.