Trying to mute an audio amplifier board – working with boards GND but not with boards pin driven LOW

[honsey]

Hello there,

I have an audio amplifier board that I would like to mute and unmute by software. The board has two pins layed out to connect a button, which basically seems to just pull that specific pin to GND.

I tried to connect a Seeduino Xiao (pin 3, others also tested) and just do these lines to pull it to ground.

pinMode(3, OUTPUT);
digitalWrite(3, LOW);

Strangely the amp just ignores this. If I connect the wire to the Xiaos GND pin the amp is muted...

What am I missing here? Hope someone can guide me in the right direction. Thank you!

Unforunately I could not find any datasheet for that amplifier module: https://www.imechappx.com/index.php?main_page=product_info&products_id=625976

Have a good day everybody,
Hans

// edit: just measured the board. Found a 1.1k pull up to VCC (in my case 12V) on the mute line.

[killzone_kid]

From TPA3118 data sheet

You might want use transistor or mosfet there instead of directly connecting it to the board

[honsey]

Thank you!

I already tried to use a PC817 optocoupler to "shorten" the two mute pins but with no success...

Can you help me what I need to search for to find an example circuit that connects GND to a PIN with a transistor/fet?

[killzone_kid]

can you post photo of the board top and bottom? it is unclear if it is using mute or shut down pin for muting

[honsey]

Okay, I just tried what made the most sense to me and it's working. Thank you!

Used a BC547 I had lying around: PIN3 with 10k on Base, Emitter to Xiao GND, Gate to the MUTE pin.

Guess that's still not 100% "compliant" but at least it's working for now

Thanks again