Maybe you´ve already found out what´s causing your problem, but if not; this info might help:
The \"dB\" is not a value \"by itself\". It indicates the value of a signal when compared to a reference called \"0dB\".
In audio, there are different references which are specified by giving the \"dB\" unit an extra letter; \"dBu\", \"dBV\" etc.
The two references mentioned are a couple of the most common ones, where 0dBu=0,776Volt and 0dBV=1Volt (audio level measuring in this case is done in Volts since analog signals are electrical).
Echo Mia´s output at \"0dB\" = \"+4dBu\", or 1,23Volt (standard in most pro audio equipment).
Audiophile output (***in -10dBV mode) at \"0dB\" = \"-10dBV\". or 0,316Volt (most consumer music audio).
The difference between these values (1,23V and 0,316V) is appr. 12dB, and this is probably the reason you hear a difference in sound level.
***In the audiophile you can select two different reference values for the \"0dB\" output - check it out in the software panel under hardware settings in the \"variable signal levels / output\" field. If you choose \"consumer\" the output level will be a little higher than if you choose \"-10dBV\".
If you have an external mixer, you match the two different levels from the audiocards by using the \"gain\"-function on the channel inputs.
Anyway, i hope it works out for you!