When building your own DIY music box you have to choose from a plethora of different options in terms of both hardware and software. In the first article of the series on my DIY music box I will focus on my thought process on the selected hardware.
Requirements
Since I feel more like a software guy than a hardware guy, I performed rather shallow research on the different available hardware options. Nevertheless, I started with collecting a list of required features that I would like the final device to have:
- Small form factor: The available space in my kitchen is very limited and I would like to hide the hardware as much as possible.
- Single power supply: To minimize the needed wiring and the number of cables flying around all everything needs to be powered by a single power supply. This also means that I would like to use passive speakers and have the amplifier integrated in the device.
- WiFi support: WiFi is a must since I do not have ethernet in my kitchen but want to stream music from the internet and my NAS.
- Bluetooth support: Sometimes you want to access your NAS or waste time with browsing the music on the music box, but want to stream directly from your mobile using Bluetooth A2DP.
Base System
I decided to take the Raspberry Pi 3 as main system board. To be honest I did not really consider choosing anything else, even though I am aware that nowadays there are various other boards available that may outperform the Pi in certain aspects. The Pi is the number one go-to SoC board for DIY projects. It is cheap, mature and has a well established community.
In comparison the its predecessors, the third Pi version features an 802.11n WiFi as well as a Bluetooth 4.1 module that already integrated. Thus, we can consider the last two requirements as satisfied without the need of falling back to separate USB solutions.
Sound Card
The quality of the Raspeberry Pi's analog sound output is rather limited due to the used digital-to-analog converter. Since I'm not really targeting high-fidelity sound for my kitchen radio I might actually be okay with this. However, the limited voltage and dynamic range requires to use active speakers if you want which I identified as no-go previously.
Fortunately, there are some specialized audio boards available for the Pi that also integrate a small amplifier. Based on my research, there two main competitors in this regard are the HifiBerry Amp+ and the IQaudIO Pi-DigiAMP+. Both boards are surprisingly similar: They use the I2C interface of the Pi and are propped directly on top of the main port connecting through the GPIO field. They offer a comparable output power (25W for the HifiBerry vs. 35W fo rht IQaudIO solution) and a certainly superior audio quality than the Pi's DAC. One fact that I appreciate particularly is that you connect a single 18V power brick and the sound card will also power the Pi and all other connected components. Thus, there is really just a single power unit involved in the end.
I decided to get the HifiBerry board since it is much easier to acquire here in Germany.
Speakers
Finding suitable speakers for my target domain turned out to be surprisingly difficult. As I mentioned earlier, I was looking for passive speakers of limited size/footprint (max 15-20cm height/width) so that they fit into my kitchen. However, since passive speakers are usually used for HiFi or PA setups almost all speakers that I could find were too large and powerful. Eventually, I was able to find satellite speakers for surround sound systems that were sold in pairs. The Dynavox AS-301 have the perfect size, power and serve a surprisingly good audio quality given their cheap price.
Miscellaneous
The last two things missing are a suiteable power brick serving 12-18V and a micro SD card. Technically, you can pick whatever you like. However, I would not recommend taking the cheapest options or at least do a minimum amount of research before. The first power supply I got made super loud high-frequency noises that you could still hear from several meters away, especially during load changes of the Pi. I sent it back to the store - the replacement is much better in this regard but still not perfect. The SD card should be at least class 6 to provide sufficient transfer rates for the Pi.