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Old 29th May 2003, 01:26 AM   #1
JZatopa is offline JZatopa  United States
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Default Can A CD-Rom be converted to a transport?

If so could someone tell me how? I know that I would loose a lot of functionality compared to a regular transport but I can live with that due to the fact that I am just a poor college student.


If not how hard is it to wire a digital out into a CD player that only has analog outs?
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Old 29th May 2003, 01:33 AM   #2
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Default Re: Can A CD-Rom be converted to a transport?

Quote:
Originally posted by DJNUBZ
If so could someone tell me how? I know that I would loose a lot of functionality compared to a regular transport but I can live with that due to the fact that I am just a poor college student.


If not how hard is it to wire a digital out into a CD player that only has analog outs?
So you basically just want a digital output to feed into a separate DAC? If so, many CD-ROM drives have a S/PDIF output on them which can be fed to a DAC.

Did you want the CD-ROM drive to be able to function independently of a computer? If so, that'd be a bit of a job (though hardly impossible) and it'd be easier to add a digital output to a CD player.

se
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Old 29th May 2003, 01:36 AM   #3
JZatopa is offline JZatopa  United States
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yeah I wanted it to be stand alone. I figgured I would find an old PS and if I remember right there is a little trick to keeping them on so I would have that running the CD-rom.


If that is to much work how would I get a digital out from a cd player? All I have is an old optimus cdplayer (I can't hack up my DVD player).
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Old 29th May 2003, 02:07 AM   #4
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Quote:
Originally posted by DJNUBZ
yeah I wanted it to be stand alone. I figgured I would find an old PS and if I remember right there is a little trick to keeping them on so I would have that running the CD-rom.
Not familiar with that trick. The trick would be interfacing with the CD-ROM drive to get your basic play/pause/stop etc., functions. Again, not impossible, but much easier to simply add a digital output to an existing player.

Quote:
If that is to much work how would I get a digital out from a cd player? All I have is an old optimus cdplayer (I can't hack up my DVD player).
Two ways. If the chipset already has an S/PDIF output, then it's just a simple matter of running a line from the S/PDIF output of the chipset to the rear of the CD player. In the event that it doesn't have an S/PDIF output, that's a bit trickier and you'd need to run the I2S into a transmitter like one of the Crystal chips. Or, if you're going to make your own DAC, you can just run the I2S out the back of the CD player instead of S/PDIF.

se
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Old 29th May 2003, 02:10 AM   #5
JZatopa is offline JZatopa  United States
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I have found CD-Roms with play, FF,FR and stop before. I just would have to find them again. Besides that what would I need to do.



I doubt this CD player has and spdif on the inside but I could be worng (how do I check?). IF it does that sound do able but if it doesnt the alternative doesn't seem worth it.
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Old 29th May 2003, 02:55 AM   #6
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Quote:
Originally posted by DJNUBZ
I have found CD-Roms with play, FF,FR and stop before. I just would have to find them again. Besides that what would I need to do.
I have too. But I don't know if they would be functional as a stand-alone just being fed from the power supply. Worth looking into.

Quote:
I doubt this CD player has and spdif on the inside but I could be worng (how do I check?). IF it does that sound do able but if it doesnt the alternative doesn't seem worth it.
It depends on the chipset. You'll need to open up the player and identify the chips being used and then get the datasheets and check out the pin assignments.

se
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Old 29th May 2003, 04:20 AM   #7
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All the CD-Rom drives that I have seen just need +12V and +5V, load a disc and away they go.
Some have front panel track skip buttons, and not all have SPDIF out.
I did see a PIC based design that interfaces to the 40PIN IDE cable and provides display and control functions.
If you don't mind listening to the whole CD, then any old CD-ROM drive will do.

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Old 29th May 2003, 09:30 PM   #8
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the key is a cd rom with 2 buttons excluding volume
I suspect that it is related to a particular cdrom chipset
but I never investigated
computer cd roms with 2 buttons will play when the button
is pressed without an ide cable plugged in
at least all the ones I tested...
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Old 29th May 2003, 10:46 PM   #9
Edgar is offline Edgar  Norway
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For fun, I tryed using a cd-rom driving a headphoneamp a few days ago, works ok. Just used a old PC-PSU and the analog out of the cdrom. It had play, FF, stop/eject and volume. Did not sound espescially good, digital out and external dac should be much better. Here is some qotes i found searching this forum and the net:

"you need a power supply to connect to the CDROM, the easiest way is using a PC power supply, but my suggestion is that build a power supply(12V and 5V) for it by LM317 or 7805.

if you want to get high quality sound, using the digital out(2-pin) instead of earphone plug or analog output(4-pin). But it means you need a DAC.

The digital out at the back of most CD-ROM drives (never seen those at DVD-drives, though) is S/PDIF format, but at TTL level. It can be converted to standard S/PDIF easily. There have been circuits on the forum

(TTL level means its 5 volts or so compard to 0,5 v in a regular S/PDIF.)

The SPDIF output on CDRom drives is not 'normal' SPDIF in electrical sense. Normal SPDIF over coax has an amplitude of +/- 0.5 Volts, the SPDIF out on CDRom drives is TTL level: 0 or 5 Volts. Be carefull when connecting the output to a DAC, not all SPDIF outputs on CDRom drives like to be loaded with a 50 ohm load! (It will draw 100 mA from the output, which is quite a lot for TTL outputs). Better is to use a conversion to go to +/- 0.5 Volts..."

Links:
www.epanorama.net/documents/audio/spdif.html
www.sound.westhost.com/project85.htm

Report if you ty it out, good luck

Ed
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