Audiophile help requested, low output level on Sony Tablet Z4

[ellebubi]

Hi everybody,
I really like my new z4, but sound output level from headphones is really low, compared to my old Tablet S (using same amplified loudspeakers, same audio files).
I tried with apps using ReplayGain technology, like Poweramp and Vanilla Music, but the output still seems unaffected.
Does it happen because ReplayGain works only on rooted devices?
Have you got any suggestions or workarounds without recurring to rooting?
Thx in advance

 

[jelbo]

Portable headphone amplifier?

 

[ellebubi]

Portable headphone amplifier?

Yes, but I would keep it simpler. As a Mac user, I find ITunes single files volume adjustment option a simple and viable option. I cannot believe the android world has nothing as simple as that.
And, I cannot understand why my old Tablet S (android 4.0.3, unrooted) performs so much better in terns of sound volume.