How do I connect differential input amp to Arduino DAC?

I was wanting to connect a 100W mono audio amplifier to the DAC of my Arduino. The amplifier uses a TPA3116D2 chip ( which has a differential input.

The data sheet explains connecting the two thus:

To use the TPA31xxD2 family with a single-ended source, ac ground the negative input through a capacitor equal in value to the input capacitor on positive and apply the audio source to either input. In a single-ended input application, the unused input should be ac grounded at the audio source instead of at the device input for best noise performance.

This isn’t very clear to me.

Is the attached circuit diagram what they mean?


The other way around.

The ground can be located at the Arduino but the amp's negative input should be grounded through the capacitor, not directly connected to ground.

And... With a 100W amplifier, I'd recommend a volume-control pot, especially during the development/experimentation phase. Plus, you might want to lower the power supply voltage to the amp and/or put a resistor in series with the speaker to keep the power down to reasonable levels. You don't really want to get a 100W "pop" when you connect something or when you power-on, etc.

Thanks Doug,

I'm not making the board but using this one which has a volume control on it:

With regard to the "pop" the datasheet goes on to say,

The impedance seen at the inputs should be limited to an RC time constant of 1 ms or less if possible. This is to
allow the input dc blocking capacitors to become completely charged during the 10 ms power-up time. If the input
capacitors are not allowed to completely charge, there will be some additional sensitivity to component matching
which can result in pop if the input components are not well matched.

Does this suggest lower value (0.1 uF?) capacitors should be used on the input?

Well that'll directly impact on the bass response... Its standard for audio amps to mute for half a second or
so at power up to avoid the thump.

Why would you need a capacitor on the arduino ground connection?

why don't try with an op-amp? :smiley:

Or with the PWM of the arduino instead of the switches.

Why would you need a capacitor on the arduino ground connection?

If you'd read the datasheet for the TPA3116D2 you'd know the answer to that...

With regard to the “pop” the datasheet goes on to say,…

I was more worried about noise from the DAC. Since the DAC can’t go negative, it (should be) initialized/biased to half the supply voltage. That DC will be filtered-out by the capacitor, but if it’s suddenly initialized to a positive voltage… “pop”. And, another pop when you power-off. It’s possible to ramp-up the bias slowly. Power-down ramp-down would be trickier.

But as long as you have a volume control, you can start experimenting at low volumes to see how it goes.