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

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: ANGEEK TPA3118 PBTL 1x60W Mono Digital Audio Verstärker Board Amp Power Module für Arduino

Have a good day everybody,

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

From TPA3118 data sheet

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

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?

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

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 :slight_smile:

Thanks again