Can anyone help. I would like to add a spdif output to any cd deck so I can use a better d/a converter. any info on auto d/a converters?
I ment to use a better d/a converter
It's going to be challenging... you've got to locate the chip that turns the CD gobbledygook into music. Very old players would have a DSP chip, then a digital filter, and finally a couple of DAC chips. With those you have to feed the clock and data lines to an S/PDIF transmitter chip like the DIT4096. Later stuff crams all that into a single chip. If you're lucky that chip has an S/PDIF output pin, which just needs minor buffering; sometimes there's an "enable" pin to pull high or low. Example: CXD2500
I haven't dug inside anything under 10 years old, so it's possible that the usable digital signals are buried inside some even more highly integrated chip. It's also possible that the deck does most things (EQ, volume...) in the digital domain, so that the outputs come direcly from a bunch of DACs. If that's the case, then there's a chance they've used some identifiable DAC chips, and if so, there's hope of finding the signals needed to feed a DIT4096.
Here's a good example of digital output mod using the DIT4096:
Thanks for the info.
My real project is to use a cheap CD HU add the s/pdif output so i can use a hi end D/A of the DIY varity. I don't care for tone or gain controls. Any Suggestions
Well, for basic playback maybe you'd be better off with a car DVD deck, which should have digital output. Drawbacks: I don't remember seeing a display (for track number, time) on any of those, and they may not resume after power cycling. OTOH they could probably play MP3s off a DVD-R which would be a @#$-load of music on very cheap media.
There's been a thread at diyaudio.com on adapting CDROM drives as transports, since almost all CDROM drives include S/PDIF digital outs, and they're cheap. I've been collecting parts to try a design I found (in that thread) that uses an AVR microcontroller to add controls and display (using a dotmatrix LCD display) to an IDE CDROM. This gizmo wouldn't support resuming, though, although if the source code is available it might be possible to add that function. I don't know how well CDROM drives handle road vibration and motion.
As an experiment, get a CDROM that has the play/skip/stop buttons on the front panel and see how it performs in car before going further. Maybe those basic functions would be enough. Another advantage of this is tray loading, which seems to me to be a much gentler way to handle CDs rather than slot loading 'em through rollers.
I have used cdroms in a car inviroment and they work very well. as u have stated u will need a cdrom with disk controles. But i used the audio out from the cd rom into the aux in on a preamp. U got me thinking.... maby i can use one of VIA Mini ITX MB's they have spdif out, video,5.1, and low power drain.Please check out the link and tell me what u think