Stereo to SPDIF?

[StevieS]

I want to build such a converter (I know I could buy one, but want to build one for myself). What are the building blocks for converting stereo line levels to SPDIF? I've looked through the Cirrus Logic site but can't decide exactly what ICs are required.

Are there ICs with built in ADCs and SPDIF encoders or does it require more than one IC? Is input filtering of some kind required in order to get the best results? I'm not looking for the ultimate audiophile output, but want to produce something that most people would find acceptable.

I work in digital electronics, but have no experience with analogue audio, so all pointers would be very welcome, thank you!

Many thanks,
Stevie

[dangus]

I haven't come across any one-chip solutions. I'm collecting parts to build an outboard ADC, and the chips I chose to play with were Burr-Brown ADCs and a TI transmitter, the DIT4096, mainly because I could get them all from Digikey. The DIT4096 is a very small surface-mount component, which will be a challenge to use.

The ADCs:
PCM1760 with separate digital filter DF1760; high performance, DIP package, expensive (and maybe almost obsolete).
PCM1800E
PCM1801 (larger lead spacing)
the last two are surface-mount, lower performance, but cheap.

If I read the data sheets correctly, these ADCs do enough oversampling and digital filtering magic that they need little or no input low-pass filtering.

Crystal Semi (now Cirrus Logic) http://www.cirrus.com/en/ and AKM http://www.akm.com/ are other sources for audio ADCs and transmitters.

http://www.hut.fi/~jwagner/electr/minidisc-spdif/ - a little board that's designed to add S/PDIF to a Minidisc player which uses the DIT4096; looks like a usable building block. There's also some hacks for adding digital out to satellite radio receivers, so if you wanted a premade board with the DIT4096 you could buy a board like this one: http://www.myradiostore.us/parts-acc...put-board.html

Now that I think about it, some older CD players with digital outs could have one of the older Crystal or Yamaha transmitters.

Maybe we can collaborate on this project...

[StevieS]

Many thanks for your info, dangus. I will look into what you have suggested.

I just came across this IC from Cirrus Logic:
http://www.cirrus.com/en/products/pro/detail/P25.html
It looks like a one-chip solution for A/D and SPDIF encoding, but it is only 18-bit. In fact it says it is for PC mulitmedia, so quite low end.

[dangus]

Here's some complete plans for an analog to S/PDIF converter:
http://www.electricstart.de/site/atospdif.htm

[StevieS]

Many thanks for the link! I'll take a look at that.