Problem: I had too many jack plugs in my room: guitar, amplifier, listening to music from computer, listening to music from vinyl disc, headphones, etc. So I always had hard time to find the proper jack plug in the cable jungle.
Purpose of this project: This project is the "firmware" of a little electronic device that allows me to select one
input source (computer, vinly, guitar), and select one output target (amplifier, speakers, headset), without having to
plug any cable.
> c:\Users\Akos\Desktop\esp-idf-2\export.bat
> d:
> cd d:\esp32\esp32-audio-channel-switch
> idf.py build
> idf.py flash
> idf.py monitor
ESP-IDF: 4.1-dirty, commit hash: 5ef1b3900
The circuit is using 3V relays to connect input signals to output signals. This guarantees that there is no added noise (eg. opto transistor would probably add some noise).
This IC is driving the relays for the audio channels; this IC is driven by ESP32 (GPIOs: 32 latch, 24 data, 33 clock)
Shift register's output signals:
- A: Computer input
- B: Guitar input
- C: Vinyl input
- D: Speakers output
- E: Headphones output
- F: Amplifier output
- G: unused
- H: unused
GND
|
| + +3.3V
[indicator led] |
|
| |
[1k Ohm] [3.3V relay]
| |
| | (collector)
+------[510 Ohm]---[BC 182 transistor]
| | (emitter)
| |
-------------------- GND
| shift register |
--------------------
Input channels have two relays always, one for Left signal, and another for Right audio signal; even if the audio source (input) is not stereo: input signal is dispatched to a Left and a Right audio bus.
Output channels consider the target: guitar amplifier is mono, so we only take signal from either left or right, and connect that signal to the bus.
- Mute button to be placed to the front board (wired)
- Muted LED to be added (not wired)
- Child lock indicator led to be added (not wired)