Fadi -

Sounds like the testing is going good. I didn't know that an option for loudness was available with the AUX connection.

I believe for my radio I used the standard connectors / inserting the pins on the end of the OEM aux cable into the connector that goes into the radio tuner as depicted in the pictures above.

The PSU / MB audio hum was unique to the combo that I set up. I have a similiar PSU / MB combo (Epia MB and M2-ATX) in the 330XI with no audio hum.

I cannot for sure pin point that the audio noise is coming from the mini-itx board or M2-ATX PS. It might be a combo of both MB and M2-ATX PS. Testing it at home with a USB based soundboard and its still giving me an audio hum.

The new combo E83 CarPC is a dual core Atom based Intel MB with a mini M2-ATX PS and has no audio hum.

What are you using for your video interface to the NAV and your IBUS interface?

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E83 - Aero PKG Mods installed: Homelink mirror. CIS-IBUS video module, AUX, Rr Dr Release, stock wheels, Remote start, CarPC (Atom) & mud flaps - NAV - MKIV - NA Map DVD - 2011
E46 - 18.5 wheels/tires (summer), 17 stock (winter), Homelink, NAV software upgrade, BMW video module, Radio to V53, AUX, USB IBUS interface,BMW alarm install, CarPC(Epia), remote starter, tank battery & angel eyes. NAV - MKIII - NA Map CD - High Version 2008.1