Right, I think I have done exactly what your after (couldnt figure how to link from resto wagen so copied across)
As a bonus, did it with a frankfurt as well, not sure if yours will be same case style though.
Well this is how I did it:
Well this was one of the more chalenging projects I have ever taken, it starts with the fact that nearly all DAB equipment at the moment (or at the time I was making this) utiilises the same chorus DAB chipset, therefore, it would make sense to use this in my system.
To gain this, I purchased a Matsui DA-1 DAB upgrade for a HIFI system its bacially a small unit that contains an LCD screen and has phono lineout to conetc to yuor HIIFI system- this would be the source for the project.
Its worth noting that there are several sites out there praising the DA-1 for its sonic qualitites (can be modified easily to mae it even better) and so that is why it was chosen - also comes with a remote control- which i'll go into in a bit.
So now I have the source, I will need a suitable amplifier and a way of controling the level i.e to the fixed gain power amp.
For the amplifier I used two TDA7256 30W mono chip amps, with a suitable selection of ELNA SILMIC capacitors (really high grade and sound awesome) - when built compared this by ear to a pioneer separate amp and guess which turned out to sound better by a long shot!!
I had decided that both the tuning and volume control would have to be digital - therefore I did a bit of engineering and came up with this solution
basically converting the existing spindles into momentarry return to center switches with a function when they are pushed in. For the digital cvoulme control I used a Dallas DS1802 digital potentionemter (the kind used in £30K + mixing desks)
Since the only way of controlling the DAB unit was through the remote control, I used the board but took connections off where usually the buttons would create a contact when pushed. I decided that I would have 4 preset stations and 4 commands to change menu preferences - display etc - trouble is how to get 8 functions from 5 buttons
The above all show how the existing buttons were utlised, a separate latching circuit was then made to toggle the operation of the other 4 preset buttons. All the connections of the remote were made remotely via reed relays (i wanted to keep the ground etc of the remote control separate to avoid issues later)
I then knocked up a brakcet the CNC machine to hold the LCD screen in place
And when assembled, it loooks a little soething like this:
I ran separate supplies for different components to the ignition and constant 12V feed so that the DAB unit and digital pot would remember their last position.
Im sure Ive missed/glazed over several key areas, please ask if you want any more detail, I think I still have some of the DXF's for the PCB's too.
In order to keep all signals as clean as possible, all audio traces were connected with OFC high strand wire:
Oh and the reason for all this, Im doing electrical engineering at southampton this year, and a like a bit of a challenge! + I did plan to do a small porduction run of these, but in my opinion it looked all a bit to 'cottage industry' - although this is but a 1st gen prototype.
Oh and in the end, the split rail supply was giving me some greif, so it was removed in favour of an 'ALPS Blue Velvet' pot, which was installed as per following image
Thanks for listening!
