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Old 27th July 2004, 09:29 AM   #1
Progg70 is offline Progg70  Sweden
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Cool Connect a DAC to a Computer DVD-player?

I have a DAC.

Can I connect this direct to a computer DVD drive and the digital out from this?

I don't whon't to use the sound card.

The plan is to take the player out and put it into a nice chassi and a good power supply and use it in mye audio set.

Perhaps there is some nice stuff on Internet who I can get tips from?


Thanks

Progg70
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Old 27th July 2004, 01:20 PM   #2
gmarsh is online now gmarsh  Canada
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If it's got a digital (SPDIF) output, chances are it'll work fine for CD playing.

Only thing is, the CDROM's SPDIF output is 5V SPDIF; you'll need to use a resistor divider and a series capacitor to bring that level down to the 0.5vpp-around-ground SPDIF spec.

Also, you'll need a means of controlling the drive, assuming your drive doesn't have the play/track fwd/etc buttons on it.
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Old 27th July 2004, 02:21 PM   #3
Progg70 is offline Progg70  Sweden
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Cool What value

Nice

What value do you recomend for the resistors and the capacitor?

How do you think the sound out will be? Perhaps the DAC is the importen factor here, not the DVD-drive who only put the digital information out in spdif, or?

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Progg70
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Old 27th July 2004, 02:22 PM   #4
OliverD is offline OliverD  Germany
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I've never seen a computer DVD drive which outputs S/PDIF for anything else than plain CDs.

Some put out a multichannel encoded stream, but your DAC probably won't know how to handle this. For the CD case, there are many projects including PCBs and software for controlling the drive via push buttons and a nifty LCD display.

If you want DVD-A or DVD-Video with 96/24 sound, the short answer is "forget it". A longer answer includes buying books about the IDE/ATAPI interface, the SCSI command set, content descrambling, making yourself familiar with the DVD file system and programming a microcontroller to read the raw data from DVD and convert it to a S/PDIF stream.

Quote:
Only thing is, the CDROM's SPDIF output is 5V SPDIF; you'll need to use a resistor divider and a series capacitor to bring that level down to the 0.5vpp-around-ground SPDIF spec.
Better remove the S/PDIF input circuitry from your DAC and drive the CS8412 directly or via a buffer.
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Old 27th July 2004, 06:28 PM   #5
Progg70 is offline Progg70  Sweden
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I'm only intrested to play ordinary CD audio, not multi chanel and so on. I have listend to multi chanel and I'm not impressed today.

I don't have any problems to control the DVD-drive, the question was abut the digital audio out. I have heard that alot of people using this for a drive to there DAC instead for a ordinary CD-player.

If there is problems they should be solvd. Buy a book when there are alot of information to share in the subject, are you a writer...
Forums are to share information you no...

I hope this is a seriouse forum....


Progg70
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Old 27th July 2004, 07:15 PM   #6
OliverD is offline OliverD  Germany
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Seems you misunderstood me

I refered you to some books because I thought you wanted multi channel or DVD-Audio. You would have been the first to take this challenge.

CD only playback is no problem at all. Just hook your DAC up to it. I'd go with a standard CD-ROM drive but DVD should work as well. As for the level matching, if you integrate your DAC with the drive anyway, feed the CS8412 directly with the TTL signal from the drive.
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Old 28th July 2004, 09:53 AM   #7
Progg70 is offline Progg70  Sweden
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Sorry from me !!

I have a extern DAC who I was using earlier with my old CD-player. The cd player is now dead.

Can you explain what what the CS8412 is? You don't think I need a resistor to take down the level of the signal?

I have tryed with a ordinary DVD-player, from mye home movie set, and I took the digital out from it to mye DAC and it works find.

A question; If I use the digital out from mye DVD-player, the movie one, gose the signal outside the internel DAC then and I use only the digital circuit?

Thanks

Progg70
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Old 28th July 2004, 04:40 PM   #8
OliverD is offline OliverD  Germany
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Quote:
I have a extern DAC who I was using earlier with my old CD-player. The cd player is now dead. Can you explain what what the CS8412 is? You don't think I need a resistor to take down the level of the signal?
The CS8412, CS8414, CS8420... are S/PDIF receiver chips and most likely you will find one of them at the input of your DAC. They have differential inputs capable of logic levels. But it is a ready-made DAC, no DIY, right?

You have two possibilities:

1. Open the DAC, see what's inside before the receiver chip and change it to make it work with logic levels. This is better soundwise if you want to build a stand-alone CD-player and integrate everything in one case.

2. Make yourself a small transformer to get the signal down two S/PDIF spec. Impedance matching is important, and the voltage divider approach is tricky. This one is easier and you will be able to re-use your DAC for other sources.

Decide and we'll tell you how to proceed.

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A question; If I use the digital out from mye DVD-player, the movie one, gose the signal outside the internel DAC then and I use only the digital circuit?
I'm not shure I understand your question
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Old 29th July 2004, 08:41 AM   #9
Progg70 is offline Progg70  Sweden
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OK then I now what the CS8412 is. I think I'm intrested to build a transformer. Where can I get a chematic for a god one on the net?

The question;
An ordinary cd-player and DVD-player have a internal DAC who you use when you connect your analoge cable to it to have the analoge signal.
Usely the DAC have a bad quality with bad sound.
If I use the digital out then I don't use this internal DAC circuits? and I use only the pure digital signal? Right?

Progg 70
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Old 29th July 2004, 12:18 PM   #10
OliverD is offline OliverD  Germany
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This converter circuit is often used in Elektor projects (if you have any issue containing a S/PDIF interface as part of a project, you will likely find pictures):

You need a small toroidal core, for example Philips TN13/7,5/53E25. Your primary should be 20 windings, secondary (to the DAC) 2 windings, both windings compact and on opposite sides of the core. Use 0.5mm insulated copper wire.

"Short" the secondary with 220 Ohms and use a 75 Ohms series resistor to connect to the S/PDIF output jack. You might want to connect the jack's ground to the chassis ground via a 100nF capacitor (don't connect them directly).

On the primary side, use some 100nF capacitors in parallel to drive the transformer from the CDROM's ouput. You might need a buffer between the drive's output and the capacitors.

This is about the point where I hope Jocko joins in and gives us some more hints.
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