I currently have an Orion COncept 97/2 digital EQ (same as the DEQ 30) It accepts toslink inputs and has it's own DA converter. What about modifying the OEM head unit to send out an unconverted digital signal to the EQ via a toslink cable, if I am correct it would allow full use of the OEM dash controls. The only thing I am unsure of is if the volume control would acutally function given that it would be adjusting a digital signel, rahter than just acting as a potentiometer and controlling voltage. I realzie this may be unchartered water and is rather exotic, but I thought I'd throw it out there, anyone have any thoughts inpu on this? It would make a CLEAN ass install

 

OK, I'll bite.

I took my head unit apart and the cd drive is controlled by a Toshiba TC9462F. You can find the data sheet at
http://www.semicon.toshiba.co.jp/en/bucat_..._2/td_26/TD.pdf



It looks like it has a built in digital output. It is in the data / bit clock / left right clock format

pin 5 - lr clock
pin 7 - bit clock
pin 9 - digital data (cd audio data)

I suppose you could send this to a Crystal CS8405 (convert data / bit /lr to s/pdif) or similar, then send that to a Toshiba TOTX199 (fiber optic transmitter) or similar and have your solution (CD section only, no volume).
Crystal part - http://www.crystal.com/pubs/cs8405A-4.pdf?...?DocumentID=877
Toshiba part - http://www.semicon.toshiba.co.jp/eng/solut...pdf/ea09705.pdf
So much for the easy part.

To address your question about the volume control and radio, the 9462 has volume control capability, but no A/D converters, so I don't think that is the part that performs volume control for the radio. The SAA7704 appears to be a mixed signal DSP that does all the volume / tone / fader controls. I couldn't find the exact data sheet, but it didn't look hopeful in the family that it would give you an easy digital out after processing. The SAA7705 data sheet (same DSP family) is at http://www.semicon.toshiba.co.jp/eng/solut...pdf/ea09705.pdf.


It looked like the signals from the cd transport are analog by that point. I figure the CD transport and radio output analog signals to the SAA7704. I think the volume / tone / etc are done in the 7704. If SAA7704 and 5 (the one from the data sheet) shared pin outs, one might look on pins 30, 33, and 34 of the 7704 for an I2S digital data stream and see if we got lucky. They both are 80 pin packages. The CS8405 even speaks I2S. Some enterprising type just might take a look at those pins

One thing that became clear to me was that the chips involved could be hooked up several ways. I should insert the disclaimer that I never hooked a scope to verify what I am claiming. I got a few clues from the silkscreen notation and sample circuits in the data sheets.

There is also a microcontroller looking chip that I couldn't ID.

It is truly amazing to see how many cool features are in these chips that never get used in the finished product. 20 filters are on the SAA7705. 10 band stereo eq anyone? On board digital crossovers with equalization? If you were open to hacking a couple of chips with a microcontroller, it could get real interesting!

 

Very interesting and VERY helpful, although it doesn;t appear to be as simple as I had hoped. I was also thinking of doing it the old fashioned way. Since my EQ has RCA inputs, A/D converters to process the signal in the digital domain, and then D/A converters (nice ones) it may be easier to use the old impedence changer technique off the OEM speaker leads. I would still accomplish the same thing and take advantage of the awesome output section of the Orion piece.

I appreciate the provided detail and it certainly elps should I choose to tinker with it myself.

Regards,
wes