Whole Home Audio Amplifier utilizing piCorePlayer and up to 10 TPA3118 50w Mono Amplifiers.
I created this to have an all in one whole home audio setup. I use a Pi 3B with piCorePlayer to operate 4 (Sqeezelite) stereo modes or up to 8 mono zones and Logitech Media Server. This is designed for a MEAN WELL LRS-350-24 power supply as it is the back of the unit and TPA3118 mono amplifier boards. At a later date I plan on creating an expansion unit to add more cards off the same Mean Well power supply and Pi.
The images of the one that I assembled has some slight differences from the STL files that are included as I upgraded some small flaws that I overlooked in my design. These are all designed and oriented to be printed with NO SUPPORTS. I printed my whole unit at 0.25 layers and 10% infill on PrusaSlicer 2.0.
The only clean up needed is to remove the 80mm fan plug inside the case for airflow.
All the screw holes are meant to be self threaded by the screws so I recommend printing the Top Cover (to test M4 holes) and an Amplifier Holder (to test M3 holes) first.
The above image shows how a PC817 or EL817 opto isolator is connected to the Pi to activate the mute circuit of a amplifier (This circuit will be used for each amplifier.). The 4.7k ohm resistor is a pull up resistor to activate the mute as soon as the Pi receives power. The Pi must pull the GPIO low to un mute the amplifier.
Testing was done to figure out the minimum required current for the circuit. The collector-emitter current is very low on the mute circuit (50uA) but, more then 6k ohm of resistance the PC817 or EL817 will not reliably saturate the chip to hold the amplifier in mute.
Configure Sound Card
Included in the files is a "CUSTOM ASOUND.CONF by mfd https://knx-user-forum.de/member/7968-mfd" and instructions on installing it to operate a typical USB 7.1 sound card to operate as 4 stereo or even 8 mono outputs. These are in .txt format so people can be opened in windows.
Modify Amplifier Recomendation
These little amplifiers have a fantastic sound as is, but to some it may not be enough. I do recommend changing the gain for better sound quality and a lower noise floor. As they are typically 32dB gain with R1 (to GND) as a 39k ohm resistor and R2 (to GVDD) as a 100K ohm. R1 can be changed to 19.5k Ohm by stacking another 39k ohm resistor on top and soldering it down so the resistors act in parallel. This will lower the gain to 26dB creating an extremely nice amplifier.
Main Parts Needed:
- 1 - Standard Size Raspberry Pi
- 1 - MEAN WELL LRS-350-24
- 1 - 5v/2Amp Switching Power Supply
- 1 - Angle Micro USB Male Plug Socket Connector
- 1 - AC Power Socket With Switch & Fuse & Lamp,Chassis / Panel Mount D4F6
- 1 - AC Power Cord
- 1 - USB External 7.1 Channel Audio Adapter (like Vantec NBA-200U (or lesser if you dont want 8 sound channels))
- 1 - 80mm x 10mm 5v DC fan. (Not required.)
- Misc. wiring depending on configuration.
Needed for Amplifiers (Dependent on how many you want to configure in unit.):
- 1 to 10 - DC 12V-24V TPA3118 BTL 60W Mono Digital Audio Power Amplifier Board Module(s)
- 1 to 10 - RCA Female Jack Socket Red/Black Chassis Panel Mount Connector(s)
- 1 to 10 - Terminal Binding Post(s) (Power Amplifier Dual 2-way Banana Plug Jack B8A7)
- 1 to 10 - PC817 or EL817(s)
- 1 to 10 - 4.7K Ohm Resistor(s)
- 1 to 2 - 50 x 70mm/1.97" x 2.76" or 30 x 70mm/1.18 x 2.76" Prototype PCB Board(s) (Depends on your circuit organization.)