Probably the easiest way to turn the volume up is to run the alsamixer command and press the up arrow cursor until the screen looks like this:
alsamixer on a Raspberry Pi

Press the Escape key to exit. You then need to store that configuration so that it is the default when the machine is turned on:

$ sudo alsactl store

• https://github.com/hzeller/gmrender-resurrect/
• http://blog.scphillips.com/posts/2013/07/playing-music-on-a-raspberry-pi-using-upnp-and-dlna-revisited/
• Es gibt einen HAT für den OrangePi: https://www.tindie.com/products/sonocotta/orange-pi-hi-fi-hat/#specs
• https://www.lesbonscomptes.com/upmpdcli/pages/upmpdcli-manual.html