Can some knowlegeable memeber please tell me the polarity of the pins on the Molex connector of CDROM spdif output please?😉
----------------------------------------------------sikkek said:
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!
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.
/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.
--------------------------------------------------------------😉Nisbeth said:
Thanks; but CDROM manufacturers tell you nothing about them except basic info anf how great they are.
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.
/U.
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.
An externally hosted image should be here but it was not working when we last tested it.
From back, digital on left, ground on right. This is from a Lite-On CD-ROM.
--------------------------------------------bstanton010 said:
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!
fmak said:
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?
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...
Check the bottom of Rod Elliot's project 85 article for details on how to do that 🙂
http://sound.westhost.com/project85.htm
/U.
http://sound.westhost.com/project85.htm
/U.
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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Thanks for all the input; some cdroms and sound card claim to have spdif as opposed to TTL. Can someone please point to sources for circuit diagrams of CDROMs.
Assuming my cdroms are TTL, they are as susceptable to cabling as spdif. Cable direction also affects thje sound. There is considerable benefit in routing connection outside computer as well. Some cdrom cables sound aweful. Why?
I have had no problems driving 75R spdif inputs but I shall try to measure the signal and may be use a buffer.😉
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Thanks for all the input; some cdroms and sound card claim to have spdif as opposed to TTL. Can someone please point to sources for circuit diagrams of CDROMs.
Assuming my cdroms are TTL, they are as susceptable to cabling as spdif. Cable direction also affects thje sound. There is considerable benefit in routing connection outside computer as well. Some cdrom cables sound aweful. Why?
I have had no problems driving 75R spdif inputs but I shall try to measure the signal and may be use a buffer.😉
About TTL levels, maybe some CDRoms have that output, but some do have normal SPDIF. Take a look at Toshiba Storage Device Division , there you have a lot of datasheets about their CDRoms and DVDRoms. I found in some of them SPDIF out stated at 0.6V. I think it was mentioned in some DVDRom datasheet, but I don't think they would change their output from model to model.
Real problem is that as many manufacturers you have, there are also that many different chipsets on CDRoms, and you probably wont know what you have at the output untill you measure it. Toshiba units use Toshiba IC's, and my NEC 32X has Winbond IC's. Didn't have a chance to open some TEAC's to see what's inside
Real problem is that as many manufacturers you have, there are also that many different chipsets on CDRoms, and you probably wont know what you have at the output untill you measure it. Toshiba units use Toshiba IC's, and my NEC 32X has Winbond IC's. Didn't have a chance to open some TEAC's to see what's inside
Real problem is that as many manufacturers you have, there are also that many different chipsets on CDRoms, and you probably wont know what you have at the output untill you measure it.
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I did measure the wave form of a Creative 52x Rom and a Teac CDRW, playing noise sigbnals from CD. Very different waveforms and clearly both TTL.
The Creative has slow square wave with two major refelections (kinks) in the risingv and falling edges. The Teac has very fast rise time and only minor overshoot on the rising edge, buit major overshoot on the falling edge.
It seems that, to get good results, one must buffer and relock the signals.
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I did measure the wave form of a Creative 52x Rom and a Teac CDRW, playing noise sigbnals from CD. Very different waveforms and clearly both TTL.
The Creative has slow square wave with two major refelections (kinks) in the risingv and falling edges. The Teac has very fast rise time and only minor overshoot on the rising edge, buit major overshoot on the falling edge.
It seems that, to get good results, one must buffer and relock the signals.
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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I knocked up a circuit with HC04 and now get a very nice square wave from the CDROM for an extrernal DAC. Why don't these manufacturers tell you clearly what to expect!
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I knocked up a circuit with HC04 and now get a very nice square wave from the CDROM for an extrernal DAC. Why don't these manufacturers tell you clearly what to expect!
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