Amplifier gain + single ended input

[Starlord]

I've got a question about gain.

http://www.ti.com/lit/ds/symlink/tpa3131d2.pdf

Let's say I have a 0.5V peak signal (consumer line level) that I'm sending to the input of that amplifier. 

Using this calculator:
http://www.sengpielaudio.com/calculator-amplification.htm

I think that if I have that signal strength and a 12V supply, I need a minimum gain of 28db to take full advantage of it.

Furthermore, I think that if I increased the supply voltage but I kept the gain and the signal strength the same, that the volume of my output wouldn't change.

So, for example, if I wanted to allow up to a 24v supply, but I assumed that my input signal would never be more than 0.5v peak, I would need a minimum of 34db of gain if I wanted the volume to continue to increase all the way up to 24V.

Is that correct?


The second question I have is about single ended input.  I want to connect a DAC to the amp.   I have previously done so using this amplifier:
http://www.ti.com/lit/ds/slos367d/slos367d.pdf

On p14, there's an example single ended input schematic which I used.

The other amp states this though:
"To use the TPA313xD2 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. For good transient performance, the impedance seen at each of the two differential inputs should be the same."

That sounds similar, but why does one have the capacitor to ground on the negative side, and the other on the positive?  Does it matter?  And why does the smaller amp have special requirements for the size of the caps used there, but the larger amp seems to just want a 1uF? 

Also, what does it mean that the unused input should be ac grounded at the audio source instead of the device input?  What would that be?  A capacitor to ground on the negative wire of the line out of the device supplying the audio?  Is that all?  I'd think that would have to be directly connected to ground so the two devices would be at the same potential.

[moffy]

I've got a question about gain.

http://www.ti.com/lit/ds/symlink/tpa3131d2.pdf

Let's say I have a 0.5V peak signal (consumer line level) that I'm sending to the input of that amplifier. 

Using this calculator:
http://www.sengpielaudio.com/calculator-amplification.htm

I think that if I have that signal strength and a 12V supply, I need a minimum gain of 28db to take full advantage of it.

Furthermore, I think that if I increased the supply voltage but I kept the gain and the signal strength the same, that the volume of my output wouldn't change.

So, for example, if I wanted to allow up to a 24v supply, but I assumed that my input signal would never be more than 0.5v peak, I would need a minimum of 34db of gain if I wanted the volume to continue to increase all the way up to 24V.

Is that correct?

Yes that is correct.

[Starlord]

Thanks!