Yes that’s it! What reason would I want anything else other than the 4.2V output?
That would depend on your audio chain/setup and how you want to handle things.
So for example, let's assume a simple setup where you have 2 high gain amplifiers connected to a DAC and you also have some high sensitivity speakers. Now, due to the high gain of the amplifiers and the high sensitivity of the speakers, it might be that you need to use the volume control at your DAC with levels at or below -40dB before you can reach a comfortable listening level.
With such a high level of attenuation being performed at the DAC, you are essentially not getting the optimal performance from it in terms of dynamic range, signal-to-noise ratio, minimising amount of intermodular distortion, etc.
There are a few ways you could deal with this situation:
- Put a pre-amp between the DAC and amps and perform the volume control at the pre-amp (i.e. DAC set to max output)
- Lower the gain in your amplifiers (if possible), or purchase lower gain amplifiers
- Purchase a DAC with an output voltage to optimally match with the gain of your amplifiers and sensitivity of your speakers
Basically speaking, if you are unsure about all this, just stick with the default 4.2V output and don't worry about it for now.