Cdrom Spdif Polarity

fmak · 21st January 2003, 07:10 AM

Can some knowlegeable memeber please tell me the polarity of the pins on the Molex connector of CDROM spdif output please?

sikkek · 21st January 2003, 08:29 AM

One of the pins is ground, this can be easily checked with a multimeter....

fmak · 21st January 2003, 03:45 PM

Quote:

Originally posted by sikkek
One of the pins is ground, this can be easily checked with a multimeter....

----------------------------------------------------
If its so easy, I would have done it. You can see on card. My point is: What is the convention on th CDROM. You can't get at it unless you dismantle. I have a manufacturer that seemed to have reversed polarity by using red on ground!

Nisbeth · 21st January 2003, 04:16 PM

What brand is the drive? Usually you can download specifications from the manufacturers website.

/U.

PS: I think I remember seing something about the polarity of this thing actually being irrelevant, because it is a TTL 0-5V signal, but I'm not entirely sure. Might be worth checking out as well, though.

fmak · 21st January 2003, 06:39 PM

Quote:

Originally posted by Nisbeth
What brand is the drive? Usually you can download specifications from the manufacturers website.

/U.

PS: I think I remember seing something about the polarity of this thing actually being irrelevant, because it is a TTL 0-5V signal, but I'm not entirely sure. Might be worth checking out as well, though.

--------------------------------------------------------------

Thanks; but CDROM manufacturers tell you nothing about them except basic info anf how great they are.

Nisbeth · 21st January 2003, 08:07 PM

What I meant was a "users manual" which has a picture of the connections on the back of the drive. I have the one for my Pioneer DVD-drive and I found a few for various cd-rw drives from i.e. yamaha and aopen. Look on the manufacturers web-site for "users manuals" or equivalent.

/U.

bstanton010 · 22nd January 2003, 05:32 PM

I beleive this is what you are looking for...

From back, digital on left, ground on right. This is from a Lite-On CD-ROM.

fmak · 22nd January 2003, 08:02 PM

Quote:

Originally posted by bstanton010
I beleive this is what you are looking for...

From back, digital on left, ground on right. This is from a Lite-On CD-ROM.

--------------------------------------------
Thanks. What threw me off is that the standard cable is shielded two core, with red not connected, white +ve and black on shield.
Why can't they use 75R coax which should be better. Some manufacturers (high class sound card) don't even shield their cables!

MWP · 23rd January 2003, 04:23 AM

Quote:

Originally posted by fmak
Why can't they use 75R coax which should be better. Some manufacturers (high class sound card) don't even shield their cables!

1. Because its 5V TTL which is used over a short distance, PC noise wont effect it.

2. Because its a PC, since when have soundcards produced good quality audio?

sikkek · 23rd January 2003, 07:14 AM

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...

21st January 2003, 07:10 AM	#1
fmak diyAudio Member Join Date: May 2001 Location: London UK	Cdrom Spdif Polarity Can some knowlegeable memeber please tell me the polarity of the pins on the Molex connector of CDROM spdif output please?

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21st January 2003, 08:29 AM	#2
sikkek diyAudio Member Join Date: Sep 2002 Location: The Netherlands	One of the pins is ground, this can be easily checked with a multimeter....

21st January 2003, 04:16 PM	#4
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	What brand is the drive? Usually you can download specifications from the manufacturers website. /U. PS: I think I remember seing something about the polarity of this thing actually being irrelevant, because it is a TTL 0-5V signal, but I'm not entirely sure. Might be worth checking out as well, though.

21st January 2003, 08:07 PM	#6
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	What I meant was a "users manual" which has a picture of the connections on the back of the drive. I have the one for my Pioneer DVD-drive and I found a few for various cd-rw drives from i.e. yamaha and aopen. Look on the manufacturers web-site for "users manuals" or equivalent. /U.

22nd January 2003, 05:32 PM	#7
bstanton010 diyAudio Member Join Date: Sep 2002 Location: Arizona	I beleive this is what you are looking for... From back, digital on left, ground on right. This is from a Lite-On CD-ROM.

23rd January 2003, 07:14 AM	#10
sikkek diyAudio Member Join Date: Sep 2002 Location: The Netherlands	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...

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