Audio player with followng features:
+ Good digital audio output (like dedicated audio board);
+ Software of player: KODI;
+ Built-in storage device (like HDD drive) for audio files (FLAC, MP3);
+ Built-in CD drive for audio compact discs;
+ Additional: power supply for external fan to cooling down old amplifier;
+ Reliable and simple computer architecture;
+ All together as cheap as possible;
Reliable and simple computer architecture present several devices. For example HTPC (home media PC with Mini ITX motherboard), but not expensive ones have got poor quality of audio on-board. From all known micro computers, Raspberry PI seems to have the biggest amount of external HIFI boards on the market. Also prices of Raspberry PI boards and dedicated HIFI boards seems to be not very expensive. That is why I have chosen Raspberry PI 3B. My budget lets me buy JustBoom Digi HAT. The most important parameters for me of this board:
+ Transceiver with 24bit/192khz with low jitter;
+ Optical (TOSLINK) or coaxial (RCA) connectors for audio output;
+ Transformer for galvanic isolation on coaxial (RCA) output;
+ Dedicated for RPI 3B (connected via GPIO);
Housing dedicated for RPI 3B cannot be used in this project due to CD drive, hard disk HDD and power supply of external fan. Additionally many users of RPI 3B is reporting overheating of CPU. Which means that heat sink is necessary. That is why JustBoom audio board should not be placed over the RPI 3B board (like sandwich). I have chosen Mini ITX housing MODECOM FEEL 302 because of:
+ low price and small size;
+ already included power supply;
+ designed place for CD drive;
On follwing pictures has been shown assembly. RPI 3B is connected with JustBoom audio board via flat 40-pin cable IDE/PATA, but one side of this cable must have changed over position of pins. Both boardes are placed on plastic plate.
Quite big and heavy heat sink is placed with thermal-tape 3M and holder with manually shaped plastic bracket.
Next to power supply board was place for 4-USB hub with additional power connector.
Cables for power supply of all devices took a place under CD drive (this place was designed for HDD, but at the beginning I have used pendrive).
For this project necessary were also:
+ 2x adapter SATA to USB with additional power connector (for CD drive and HDD drive);
+ Several panel mount cables for HDMI, Ethernet, USB (for moving connectors form RPI 3B into the back plate of housing);
First test and immediate improvements:
+ RPI 3B does not work with red micro-SD card form SanDisk, but it works fine with white micro-SD card form SanDisk. I do not know is it problem with red card or only with my piece of RPI 3B. Both cards are 16GB and class 10.
+ KODI with standard Confluence skin seems to be quite heavy for RPI 3B, I have noticed (with quite big heat sink already installed) temperatures 50~62*C after several hours of using. That is why I have extended heat sink with L-shape aluminium elements and I have installed internal fan for cooling (low rotated speed, size 70).
+ Pendrive 64 GB it is not enough space for music in FLAC files (one song has around 20~30MB), much better solution is HDD drive size 2.5 inch and 1 TB space.
+ Both devices (internal fan and HDD) have been assembled under upper cover of housing.
+ After 14 hours of playing music and using KODI skin I have got 39~42*C. In next days I have noticed max temperature 47*C.
Cheap audio player based on RPI 3B and JustBoom plays really nice (digital audio goes to processor device then analog audio goes to amplifier and next stereo speakers). Additionally external fan is cooling amplifier designed in middle of 90s. JustBoom Digi HAT seems to give better quality audio from optical (TOSLINK) output than coaxial (RCA). In the housing made from steel (like in this project) WI-FI may does not work correct, internet should be connected on Ethernet cable. Thank you to my colleague Grzegorz, he has helped me a lot in this project.