how many wires needed from CD to sound card

[DJW]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.
My question is can the stereo hook up shared common leads? So only one
needs be wired to ground to be able to do stereo? And if so does it
matter which of the two grounds is used. Also if I were to make up the
connection with four wires would it matter anyway?

 

[GMAN]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.
My question is can the stereo hook up shared common leads? So only one
needs be wired to ground to be able to do stereo? And if so does it
matter which of the two grounds is used. Also if I were to make up the
connection with four wires would it matter anyway?

Why are you wanting to hookup an analog cable from the cd to sound card?

You havent needed to do this since Windows 95 came on the market. Any modern
CD or DVD drive made since 1994 or so carries the audio digitally thru the
EIDE or SATA cable.

 

[Sjouke Burry]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.
My question is can the stereo hook up shared common leads?

Yes.
Yes.
No.
No.

 

[Paul]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.
My question is can the stereo hook up shared common leads? So only one
needs be wired to ground to be able to do stereo? And if so does it
matter which of the two grounds is used. Also if I were to make up the
connection with four wires would it matter anyway?

I have two optical drives here, that came with CD-audio cables.
Each cable has three wires.

*******

This is from the ALC650 datasheet. (That is a motherboard audio chip,
one that interfaces to a four pin CD audio input, amongst other things.)

http://img62.imageshack.us/img62/1354/cdaudio.gif

The chip (an AC97 codec used on motherboards), actually has a three
pin interface on it. It has CD_L, CD_R, CD_GND. The ground is only
on one end (I think, the drive end). Where CD_GND is on the AC97 chip,
the connection is AC coupled.

The idea behind this, has to do with noise. The CDROM audio cable
functions as an antenna. All the wires pick up noise. The noise is
"in-phase" and has identical amplitude on each wire. Even the ground
wire, has the noise imposed on it.

When the three wires arrive at the CODEC chip, the differential amplifiers
are present. (CD_L minus CD_GND) is the math the left channel diff amp
provides. Say there was a 1 volt noise sine wave on both of those wires
(i.e. on the ground wire and on the left channel wire). When the differential
amplifier subtracts the two signals, the noise cancels out. And it cancels
out, as long as the noise coupled into each wire is equal. It the noise
in one wire, has a higher amplitude than the noise in the other wire,
then the noise will "leak through".

CD_Player CD_L --------------||------- AC coupled into
CD_R --------------||------- the dual differential
solid earth ---> CD_GND -------------||------- amplifier circuit
on this end

Now, if you had four wires total to work with, and twisted together
CD_L with a CD_GROUND_L wire, then a more precise differencing could be
done. That may have been the original intent. But the three wire thing
does much the same thing, as long as all three wires are co-located
(close to each other), for best matching of noise signal levels. And
using only three pins, on the chip, saves a pin. So even if you used
a four wire cable, the three pin interface on the chip, may remove
any benefit it might have provided.

As the other posters note, using DAE (digital audio extraction), bypasses
the need for audio cables. But this doesn't work on older optical drives.
A newer drive should support this tick box. The advantage of DAE is,
in theory there is no noise. But I'd still want some way to verify,
that I'm making an exact copy. It isn't guaranteed, that all drives
rip the same way.

http://h10025.www1.hp.com/ewfrf-JAVA/Doc/images/c00220931.jpg

Paul

 

[Jon Danniken]

You havent needed to do this since Windows 95 came on the market. Any
modern
CD or DVD drive made since 1994 or so carries the audio digitally
thru the
EIDE or SATA cable.

I needed to do it with my win98 box, because the processor would bog down if
it had to do the D/A instead of farming out the job to the processor on the
sound card. I think that was a P2 at the time.

Jon

 

[Jack]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.

My question is can the stereo hook up shared common leads?

This question is not precise enough to be answered. It requires that a
potential answerer make assumptions

So only one needs be wired to ground to be able to do stereo?

This question is not precise enough to be answered. It requires that a
potential answerer make assumptions

And if so does it matter which of the two grounds is used.

This question is predicated upon an imprecise question that requires a
potential answerer make assumptions

Also if I were to make up the connection with four wires would it matter anyway?

This question is not precise enough to be answered. It requires that a
potential answerer make assumptions

 

[Flasherly]

I want to make up a cable to go between my sound card (sound blaster
live PCI)and my CD-ROM drive. I know the right and left channels wires
are the furthest out to both sides of the plug. And I am fairly
certain that the ground (common) is the center two wires on the
connector. I did a quick look to see what was available on ebay and
from the photos of cables it looks like they only use three wires.
My question is can the stereo hook up shared common leads? So only one
needs be wired to ground to be able to do stereo? And if so does it
matter which of the two grounds is used. Also if I were to make up the
connection with four wires would it matter anyway?

I've seen both four and three and modified their connectors to make
the left one fit into the other, right one. I wouldn't sweat giving
it a shot -- nothing to worry about like the unforgettable flash left
in those undischarged killer coke-bottle capacitors.

But it matters.

I run mine, occasions for a computer optical device with a Turtle
Beach soundcard (gave up on SoundBlaster) variously through Behringers
-- a XENYX 802 2-bus stereo mixer and a Ultra-Curve DEQ2496. Both
contain processors, rudimentary mixing opamps on the 802's line's
schematics for further dithering three or parametric EQ stages before
stereo width focus, on the DEQ2496. A two tape-loop on a Carver
amplifier contains the final mix with one loop being an old DBX
Compander/Expander and other the DEQ2496. Both DBX and DEQ2496 have
provisions for auxiliary returns out, the DEQ2496's further from the
aforementioned Stereo-Width-Focus stage, I've returned by way of Ch.
Banks 3/4 and 5/6, for two mixed channels into the XENYX 802 mixer.
The end effects are superimposed upon "dry" signal from Turtle Beach,
as adjustable to a sum of either or both tape loops "wet" signals.
Even though L/R balancing on the 802 is a "summed soundstage mixer-
feature", so there's never quite a loss of either channel at either
extreme, it's nevertheless an understatement not to ensure stereo
feeds are integrally routed.