Same problem here, but I have plenty of available workarounds so it's hardly a deal-breaker. For example, I also have a Note 10.1 Tablet and the sound output is much louder and with apps like Spotify and Bubble UPnP, I can use my phone simply as a remote to control the interface while the Tablet is connected to the listening device. I also have a lot of pro audio gear including small mixers, pre-amps, powered studio monitors, loudspeakers as well as home theater equipment so in most situations I am able amplify the signal beyond the limit anyone would ever want (or could tolerate) without any distortion. If I am on the go and additional equipment is not an option, sometimes I will enable the "sound booster" on my equilizer app (paid version) which does give a decent boost to the overall output level.
Hope this helps!
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