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-   -   CDROM as CD players (http://www.diyaudio.com/forums/everything-else/6074-cdrom-cd-players.html)

Lisandro_P 16th September 2002 05:21 PM

CDROM as CD players
 
I know this was discussed (somehow) before, but i just can't find the thread, so here it goes :xeye: ... has anyone tried using an old CDROM player as the heart of a homemade CD player? You can get "old" (x6) CDROM drives for cheap (if you don't have one laying in a closet already) that are VERY rugged, have an IDE interfase, and spit both analog audio & S/PDIF data if you hate internal dacs' :). I don't know how hard would it be to hook one to a microcontroller through.... any ideas/comments?

newmz 16th September 2002 08:03 PM

what do you want the microcontroller for? lcd display?
they generally will operate without being connected to a pc, you just need a small power supply with the molex connector for the 12v and 5v lines.

i have one that is an old drive that has all the transport buttons on the front (drivebay) panel under the drawer - i.e. it has the open/close button, play, next, previous and stop. A lot of them just have open/close or maybe just a play/next too. i was lucky enough also to have some little old power supplies i got out of some old 10bps ethernet hubs, just a little switchmode supply with a single molex output - perfect!

i made up some connectors to convert the little 4-pin analog output to rca sockets and i just run that a short distance to my pre-amp. you can also do this via the headphone socket (i think).

i actually ruined a newer one that has a 2 pin digital output as well, i was going to build an spdif stream dac for it maybe but then i went and wired the molex connector wrong and had the 12v and 5v line reversed! so i fried something :bawling: badly - it released some of that "magic smoke" that you find in electronics - you know about that stuff? it's what makes electronic components work, so if you make some mistake and it escapes, they are ruined ;).

Lisandro_P 17th September 2002 04:13 AM

The microcontroller would be to avoid using the front buttons :) Besides, you could add a nifty display, programming, shuffle and other things that you miss when you don't have avaliable without much sweat. For the psu a 9vac transformer and a regulator for the 5v are more than adequate i beleive (the 12vdc are used for the "power" devices such as servos, motors, etc, so it can go unregulated). All the micro has to do is to send MFC commands through the IDE port (things like "gimme the table of contents", "start playing track X", "go to time frame XXX") and the CDROM drive makes the rest, that's what makes it so appealing to me. You strip the case, mount it on a nice box, put a new front panel on the tray :) and you're set!

How did you like the analog output of the cdrom compared to a regular CD deck? I found the threads a bit after i posted this :) but no one commented on their results. I have to try both the analog output and the S/PDIF connected to a nice D/A, but i just checked out an old cdrom i had lying arround (which is unsuitable for me as the tray is NOT motorized, a pitty...) and the sound quality was VERY good right from the headphones output. I imagine sticking a buffer to the analog out would be even better...

Ah, and about the "magic smoke"... i ran into it more times than i'd like to remeber, yet i somehow manage to keep popping it up :headbash: I feel your pain! :)

r_s_dhar 17th September 2002 05:10 AM

CDrom as Stand-alone-player
 
Dear Lisandro,

Your idea is quite feasible. But "learned" people do not advice this. I remember to have asked Tomi Engdahl (you surely know this famous guy and his site) about this. He said, among other things, that a CDrom's DA conversion is not quite upto the HiFi mark and that a CDrom drive has unnecessary complications like error correction circuitry.

I would like know how, vis-a-vis a dedicated audio CD player, a PC CD Rom drive would perform quality-vise.

Could you tell me?

Lisandro_P 18th September 2002 12:31 AM

Re: CDrom as Stand-alone-player
 
I'm not arguing about the cdrom's D/A conversion to be nowhere as good as a good hifi cd deck (which doesnt means it sucks like a CD walkman either, but still...). The thing is, a CDROM unit gives you a CD transport with motorized tray that can be controlled with relative ease... and spits S/PDIF data. The rest is unimportant, as you would simply be ignoring it.

As for the quality, it all depends on your work :), but old CDROMs drivers in particular are surprisingly rugged, and i doubt you'd get a cleaner *DIGITAL* data stream (without errors) from a CD player than a multispeed CDROM...
All in all, it's just an idea. Sooner i might build one of those small ESP DACs which looked nice and simply hooking it to the CDROM to see the results. If its any good it might start a new project!

Jocko Homo 18th September 2002 03:32 PM

Problem is......
 
Most digital outputs are flawed, from a transmission line point-of-view. They need lots of work to get good results. Not hard, but there is not much room in one of those things.

Jocko


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