Finally i made sum investigations.
When mirc is using a soundcard, i tested it with "rme multiface" and now "creative pebble x speaker with internal usb soundcard", in both cases a running mirc eats 2 watt more power.
Now i had the idea to block mirc to access windows audio with sandboxie.
So i added "ClosedIpcPath=\RPC Control\AudioSrv" to the sandboxie.ini.
Then i start mirc inside sandboxie and voila ... 2 watt less energy consumption (25 Watt, instead of 27).
Maybe it isnt a very exact measurement because i use the power consumption measurement of an apc ups.
But it clearly shows that an always "touched" windows audio can generate unnecessary power consumption.
No matter, i can live with the sandboxie workaround

thx.
