Connecting symmetrical output to input with GND

Thread Starter

Piotr Mackowiak

Joined Aug 17, 2019
9
I have MP3 module, control via I2C, dedicated for RPi or Arduino usage. Such module has symmetrical output (probably on-chip D class amplifier) with OUT- and OUT+ pins. None connected to GND. Output is dedicated for high impedance loudspeaker (over 30 Ohm). But I want to connect it to input of the amplifier with SIGNAL and GND pins. How can I do it in the most simple way?
 

KeithWalker

Joined Jul 10, 2017
413
I have MP3 module, control via I2C, dedicated for RPi or Arduino usage. Such module has symmetrical output (probably on-chip D class amplifier) with OUT- and OUT+ pins. None connected to GND. Output is dedicated for high impedance loudspeaker (over 30 Ohm). But I want to connect it to input of the amplifier with SIGNAL and GND pins. How can I do it in the most simple way?
Connect either of the output pins the the input of the amplifier using a suitable capacitor, 0.1 to 10 uF, depending on the input impedance of the amplifier. If you use a polarized capacitor, connect + to the output pin of the MP3 module.
 

Thread Starter

Piotr Mackowiak

Joined Aug 17, 2019
9
I thought about such solution but I have my doubts. MP3 and amplifier modules have different VCC but the same GND. That's why I don't know if the whole thing will work correctly.
The symmetrical output of an MP3 module has a relatively high output power (because it can handle the speaker), which when connecting OUT- via a capacitor to GND, can damage potentially the module. The problem is not its price (about 1,5 USD) but the time of delivery from Ali (50 days with free delivery).
So won't I damage the module with the solution You suggest?
And one more problem. If the output of the MP3 module is a really D class amplifier, it needs some inductance at the output for correct operation (necessity of integration). So what to do about it?
 
Last edited:

KeithWalker

Joined Jul 10, 2017
413
I thought about such solution but I have my doubts. MP3 and amplifier modules have different VCC but the same GND. That's why I don't know if the whole thing will work correctly.
The symmetrical output of an MP3 module has a relatively high output power (because it can handle the speaker), which when connecting OUT- via a capacitor to GND, can damage potentially the module. The problem is not its price (about 1,5 USD) but the time of delivery from Ali (50 days with free delivery).
So won't I damage the module with the solution You suggest?
The output of the MP3 module is a bridge circuit. The two output pins have identical outputs that are180 degrees out of phase. The capacitor is not connected to ground, but from one of the output pins to the high impedance input of your amplifier. Connect the ground of the MP3 player to the ground of the amplifier. It will not damage your MP3 player.
 
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