I ran across this little tidbit using Google (link)
This a response from Christian Bakken at Hegel when I asked him the same question about XLR and H390.“Hi Rob,Please note that there is absolutely no point in using XLR connectors unless the signal path is balanced, all our XLR outputs and inputs are balanced. "Fully balanced" is a pleonasm, a circuit is either balanced or not.Best regardsHegel Music System AS – Oslo, NorwayChristian “
The Aqua La Voce S2 specs note ’asymmetric’ XLR output. That seems to imply that it is not a balanced output but a voltage doubled single ended output using an XLR connection. So probably not an ideal situation for the amp’s balanced inputs from Hegel’s point of view.
Here's an article explaining the difference between balanced and unbalanced connections - link.