How to add Aux Input for Sony CDX-MP30

When I first decided to buy it, I saw a back picture and found that there is a pair of Audio In Jack. So I though it did have rear Aux Input.
But later, when I read the user manul, I found no way to select the source to be Aux Input. The only thing I found is that the Aux Input is not a stand alone Aux input. In stead, it is Bus Audio Input, used together with the Bus Control Input, for connecting an external CD/MD changer. Does it mean that I can use the Audio input only if I connect sth like CD changer to communicate with the receiver via the control BUS?
I tried to feed mere audio to the audio in without connecting BUS changer, and the unit refused to take my external audio....
Then what shall I do?

Thanks!

https://www.crutchfield.com/cgi-bin/S-jt8UA2DFEjB/ProdView.asp?a=0&s=0&g=62700&id=detailed_info&i=158CDXMP30

It appears as if you have an optional aux input for which you need the Unilink adaptor? XA-C30 Retail $100.  Or you need a compatible Sony Unilink device. 

Unless somebody else out there knows and replies...You could pose the question to one of the official distributors of Sony Car Audio.  They might prove helpful. 

Interesting question since I am considering a Sony HU at this time. 

Actually, not XA-C30. It's used to transform the original single changer input on the Sony receiver into 3 selectable changer inputs.

I know, that XA-107, or XA-300 seems to do this job, ie, adapt the CD changer input on Sony receiver into an extra Aux input as well as retains the CD changer input.

But my question is, isn't there anyway that I can bypass the the CD changer control BUS communication and just feed mere Aux signal into its changer's BUS audio input jack?

I never have a way to know the BUS control interface? Do I have to satisfy its BUS control protocol before I use its Audio Input???

Well, I sufferred this a lot, from my OEM honda cassette head unit (which also comes with M-BUS changer control but can not used directly as an Aux input) to my current Sony head unit.

Any suggestion that I can manage this in a simple way? like a simple jumper wire in the BUS control jack?

I figured that's what you were getting at.  You seem more inclined to open up the unit and fiddle than I am.  That being said, this shortcut was posted previously and  may or may not give you ideas about obtaining schematics.  Good luck.

https://www.geocities.com/blhobbs.rm/Mazda_stereo.html

Thanks. F4Pilot.

Do you know where I can find the pin layout diagram for the Sony receiver's changer control BUS? I wanna have a try to fool the head unit as if I had plugged in a CD changer so that I can use the Aux input directly for my external mp3 player.

Thanks again.