Single ended mono input to stereo amplifier?

[Starlord]

Hello,

I want to have a single-ended mono input to this amplifier:
https://datasheets.maximintegrated.com/en/ds/MAX98306.pdf

But there's two things I'm not sure about.

My first question is:

Why do both of these TI amplifiers connect the single ended input to the - side of the... op amp? and ground the + side?
And does it make a difference which side I connect my input to, and which side I ground?

http://www.ti.com/lit/ds/symlink/tpa6211a1.pdf
http://www.ti.com/lit/ds/symlink/tpa2012d2.pdf

From this Adafruit tutorial for a breakout they offer, it doesn't seem to matter, as they have grounded the - sides for the single ended input example, but then, it doesn't make sense why TI would choose to ground the + side if they could pick either one.

https://learn.adafruit.com/stereo-3-7w-class-d-audio-amplifier/inputs-and-outputs

And my second question is, do I need four capacitors here, or could I have one capacitor for the single ended input to both left and right channels (let's say the - side), and another capacitor to ground, which is connected to the opposite input (+ in this example) for the left and right channels?

[Zero999]

Those are not operational amplifiers.

They all have a fixed (other than the TPA6211A1, which can be set by varying the input resistors) relatively low gain, compared to an op-amp, and automatically bias the output at an average of half the supply voltage, thus eliminating the need for additional resistors.

The TPA6211A1 and TPA2012D2 don't need any input capacitors, if the inputs are both within 0.5V and _DD-0.8V (this is the common mode range), otherwise, use input capacitors and allow the inputs to bias themselves.

The MAX98306 need input capacitors, otherwise it will upset the internal biasing.

Because the inputs to the amplifiers are differential, either input can be ground or signal, the only difference is, if the signal is at the inverting input it'll be inverted.

If you want to connect a stereo amplifier, to a mono source, just connect both the inverting and non-inverting inputs together (no capacitors) and then connect one to ground and one to the signal, each via a suitable capacitor.