How do you get bit-perfect playback on the Apple Music app?

[palm]

Normally, the volume control on the phone defaults to about 1/3 from zero. Can't hear it at all. This is normal. Since the Airport Express v2 is linked to a DAC and RCA into my amp, I control the volume from the amp. This is normal for Airplay (1) and produces the best Airplay sound. Consequently, I normally raise the Music app slider volume from 1/3 to full so it is also as close to bit perfect as I can get it. But if I leave Music, like to check another app, when I come back to Music, the slider drops about 5-10%!

I have a Belkin Soundform Connect and I confirm that the volume is generally indeed at about 1/3rd when connecting. I also put it to max.
But I don’t have the issue that volume resets to a lower value.
The fact that volume is conservatively set low after a while is not new according to me, I observed this back when first HomePod was introduced. And I think it makes sense: you don’t want such Airplay “speakers” to blast at the potential high volume you left it.
I think the inconvenience we both face originates from the fact that we need to set the volume to 100%. This isn’t how it should be. When you connect the RME ADI to an iPhone, iPad or Mac, the volume slider is disabled : this is the correct behavior IMO