OK, thanks.
I hope Babyface will notice external power supply and will stop receive electricity from computer.
Yet, I would like to hear how does it precisely works from anybody who tried that , and what's the result.

Thanks everyone here.

Robbertino

They are not stupid, but I'm afraid for my device cause
I have very strong 12.5 V battery
so I do not want to risk with aditional 5 or 6 V from comp.

Thanks

Thanks folks.
Today I bought cheap (9.60 euro) power supply (with options 2.5 V, 5V, ..., 12 V),
and I didn't notice any change in sound (for now). (With windows 7 + Fidelizer + Sony Sound Forge.)
Just to share it with you.
(Path: Notebook  -> Babyface -> Pass Aleph -> Speakers).

I would note for others interested in this topic that it has been discussed in this forum in the past.

The power supply for the BabyFace (and other RME devices taking battery power) is very flexible.  The voltage requirements are shown on the label on the underside of the Babyface (6 - 12V).  In previous posts it has been confirmed that it will safely accept power from a car battery system (nominal 12.6V, maximum on charge about 14V). It needs a power supply capable of delivering at least 1A.

It will also accept AC as well as DC, which means that you do not have to be careful about the polarity of the DC connection.  And it is very good at rejecting noise on the external power.

And connecting an external power supply means no current is drawn from the USB connection (saving drain on the laptop/netbook ... iPad??? ... battery).

Ok guys.
I've never seen an audio device that isn't  dependent of the
kind of electricity source. YET.
Recently my student took a cd player and made it a really nice device
by giving to almost every important part a quality power source.

But, maybe RME engineers really know how to do it.
So, on this forum no one spot the difference (in sound) between usb Babyface and battery powered Babyface.
Ok. I'll check with my devices and cables.

Noise on dc is some remaining ac harmonic content on the rectified dc, clicks, interference, switching transients and ripple control tones from the mains itself. 

If, as is possible, ac is used, then this could be regarded as pure noise with no dc.  A good internal power supply/regulator can rectify and remove all the ac harmonics leaving only dc with virtually no ac content.

Electronic circuits of balanced configuration are often designed to further reject (or cancel out) noise on the power supply ("common mode rejection") to achieve low noise levels such as the Babyface demonstrates..