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| author | Aurelien Jarno <aurelien@aurel32.net> | 2020-04-13 15:49:14 +0200 |
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| committer | Aurelien Jarno <aurelien@aurel32.net> | 2020-04-13 18:41:39 +0200 |
| commit | e7101511824d54e836f4b6ccee630aef118a1ade (patch) | |
| tree | 7b0906a0c38f70e56e60fe5e92d22830bc9066c0 | |
| parent | a02253dee2a7a345406173ed58b44418159df42b (diff) | |
| download | rpi-amp-e7101511824d54e836f4b6ccee630aef118a1ade.tar.gz | |
Add README.md
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diff --git a/README.md b/README.md new file mode 100644 index 0000000..7fa2427 --- /dev/null +++ b/README.md @@ -0,0 +1,72 @@ +# 2 x 30 W RMS Amplifier for Raspberry Pi + +This 2 x 30 W RMS Amplifier for Raspberry Pi is an open source project based +on the [TAS5825M](http://www.ti.com/lit/ds/symlink/tas5825m.pdf) chip from +Texas Instrument. It takes the form of HAT, that back-powers the Pi. + +While its output power is relatively limited, it sounds great and for me it's +a big change from my previous DAC, preamplifier and amplifier, all in 19" +enclosures, for basically the same performances. It's incredible how such +a small chip can output so much power with so good quality. + +I am using it with a Raspberry Pi 3B+. I have installed +[PulseAudio](https://www.freedesktop.org/wiki/Software/PulseAudio/) on it, +that way I can play audio remotely from various computers. + + +## Photo + +[](images/rpi-amp.jpeg) + + +## Hardware + +The board has been designed using KiCad. The [schematic](images/schematic.png) +is inspired from the TAS5825M evaluation module. It is used with a +10µH / 680nF output filter, using the same Murata inductors as in the EVM. The +PVDD power supply is bypassed with 2 x 680 µF + 2 x 10 µF ceramic + 100 nF +ceramic capacitors per channel. There is also a 5V 3A DC/DC converter based on +a LMR33630 to back-power the Raspberry Pi from the 24 V power supply, and a +LTC4365 based DC input protection to protect the board from wrong polarity, +under-voltage or over-voltage. The board accepts voltages between 20 and +28 V. The 3 GPIO outputs from the TAS5825M are connected to 3 red LEDs, +that might be configured to display various information (fault, warning, +auto-mute, etc.). Finally the board also contains the 24LC32A EEPROM required +for Raspberry Pi Hats. + +The PCB is a simple two layers PCB that follows the +[Raspberry Pi Hat requirements](https://github.com/raspberrypi/hats), although +it doesn't have the optional display flex cutout, the optional camera flex +slot, nor the 4-pin PoE header. + +All the components from the [bill of material](BOM.txt) should be easily +available from distributors that also sell the TAS5825M. They might be +difficult to solder for people not used to SMD, especially for the LMR33630 +that has an exposed pad and for the TAS5825M that is using a QFN32 package. It +is possible to solder both using a hot air gun, I have personally not used +a stencil. + +The board should be powered by a 24V / 90 W switching power supply power +adaptor. + + +## Software + +The software part is not yet finalized. I have written a quick and dirty +Linux kernel module to present the TAS5825M chip as a simple audio card. +The driver doesn't support any of the advanced features of that chip (volume +control, audio processor, etc). It is also not good quality enough to be +upstreamable. It has been sufficient for my usage, so I didn't take the time +to improve it. + + +## Sources + +All the sources of the repository are available +[here](https://git.aurel32.net/electronics/rpi-amp.git). + + +## License + +The contents of this repository is released under the +[Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0)](LICENSE). diff --git a/images/rpi-amp-small.jpeg b/images/rpi-amp-small.jpeg Binary files differnew file mode 100644 index 0000000..dcb0c3b --- /dev/null +++ b/images/rpi-amp-small.jpeg diff --git a/images/schematic.png b/images/schematic.png Binary files differnew file mode 100644 index 0000000..170533a --- /dev/null +++ b/images/schematic.png |
