Now that finally I have all elements together to actually use the device for its main intended purpose (most of the time it will be used as a music player) I had to discover that the base-level of noise is unacceptable high. It is impossible to listen to music with low volume, e.g. in a silent environment, as simply the base noise is filling your head. This of course depends on the sensitiviy of your headphones, but is already audible on my Koss Porta Pro (60 Ohms) and unacceptable on my CX-300 (16 Ohms). On my old Tornado (and even my Amadeus) it was just audible with the CX-300, but not with the Porta Pro.
I am much disappointed and only a very slight hope remains to increase the volume on one hand (the max volume is rather low compared to my Tornado) and decrease the sensitivity of the headphone on the other (serial resistor).
Seems to develop to a never ending story with this device :-( and I suspect that there will not be a happy end.
I have not found any option in the registry for increasing the sound volume when the headset is connected. The sometimes reported action to set the valule in HKCU\ControlPanel\Volume to Volume=0xffffff is nothing but the place for the System Volume that is adjusted with the volume keys anyway. Even snapshotting the registry with and without headset connected and comparing these has not revealed an option.
As the noise level cannot be changed - and the volume not increased, I fear that was my short love story with this little gadget :-(
It still fits for anyone that has a lower sensitivity headset and does not require higher volume sound level there.