[SOLVED] Two sources to one amplifier board

Projects General Guidance
1

I have currently a "DF mini player" that is connected to an XH-M543 amplifier over the DAC gpios.
miniplayer_pin_map
44295953

I have another project with A2DP that is connected to an external decoder board (see picture below) and is also connected to a separate XH-M543 and that works to. (LGR is connected)
2021-10-13_000307

Now my question is... Can I connect those two sources to one amplifier with only one esp32? I prefer to keep this amplifier. I could wire them together i think... Do I need a DC blocking cap and a voltage divider to do that. Or are there other, better ways to do that?

2

You need an analog mixer for the audio. Wiring the outputs together directly could damage them. The question of ESP32 compatibility is a different issue that I will leave to ESP32 experts.

Kind of hilarious that they labelled the amp output as an input. :slight_smile:

3

Excuse me if I didn't enplane myself very clear. I know it will work with an esp32.

Would this be OK?
2021-10-13_005640

4

It should be just fine.

5

Connected like this?

Naamloos
Naamloos1407×920 118 KB

I have already bought one, but it doesn't fit in my E-box. I could drill a hole... but if there is a solution without this mixer, I would like to hear from anyone?

6

You can get a much smaller mixer than that. A simple mixer can be a resistive junction. 3 resistors. But since that is a lossy mixer, there's usually an amp with it. You might find some gain settings with the sources and power amp, that allow headroom for the small losses.

Here is one example:
https://stufinnis.co.uk/stereotomono.html

7

So I could add just a few resistors in my cable.. I don't need to adjust the gain with a button.

This is what I found now on your advice...

0RFbQ

I believe this is for a 12v application to keep arround 30ma on the line. I think I have to change the resistor value. It could be very low because I have 3.3v application. What would be a right value of the resistor?

8

Following my calculation I have 30ma to much soo if I do 3.3v/0.03=110ohm to keep the 30ma on the device. Can anyone confirm please?

9

Audio has nothing to do with milliamps. :astonished: The 1k resistors will be quite fine.

10

considering I don't have much space, two 1K resistors are the best solution for me.

I will follow this schematic

0RFbQ

Thanks @anon57585045 and @Paul_B for you advice.

11

I have tested it and works!

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12

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