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December 4, 2009, 4:24 pm
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Because they're so bulky and seldom used/needed I never had a CD/DVD
reader/writer. But now I bought one from a friend, who's son apparently
didn't like it. I'm guessing that the 'sound' is damaged ?
It's a 'Samsung writemaster': standard 40-pin IDE cable type, fitted into
a USB interface box [which is nice, since the inner guts can work with
my old-old-PC too, which has no USB].
Reading/writing CD, data or a sound-trak/s works perfectly, after
I used cdpananoia [under mandrake 9] to copy and move 1.4MB
of a trak to the box which has a speaker, to confirm that the
partial-trak sounds on the PCspeaker. Nothing is easy !
AFAICR messing with old CDROMs previously: connecting the
4-way audio output to amplifier allowed hearing the sound, and
trak-stepping by the 2nd button [besides the 'door' button].
The old CDROMs had a hardware volume adjuster too.
Q1. since the samsung has got an analog-audio-output, which
goes to 2 left/right RCA connectors, it must have an audio output,
so is this at a standard level/amplitude with the range that older
CDROMS with volume-control output ?
Q2. What format does the 2-pin audio-digital supply
Re: CD/DVD output formats.
These are just some guesses.
If the back of the drive has a four pin audio interface, the
levels on there would be "line level" or about 1 volt RMS. That
is suitable for a line level input. If the CDROM drive is installed
inside a computer, a four wire cable would connect the analog audio
output of the drive, to the sound chip. There could be a four pin
header on the motherboard, next to the built-in sound chip
on the motherboard. If there is a separate PCI sound card (like
a SoundBlaster), there might be a four pin header on there.
(This probably isn't the right cable, it's just to illustrate the rough idea.
When you buy a raw drive mechanism, in retail box, this cable may be included.)
If the drive was housed in an external enclosure, with two RCA
connectors for the audio output, you'd go to RadioShack, and convert
the two RCA connectors to 1/8" stereo miniplug. Then plug that into
the "Line In" on the sound card faceplate on the computer. This
is an example of stereo male RCA to 1/8" stereo miniplug, suitable
for plugging into the "Line In" on the back of the computer.
The two pin "digital" output standard is likely SPDIF, but
may not share the electrical specification of SPDIF.
In the table here, you can see the "real" SPDIF specs. This
is for making a connection from the computer to your
AV receiver/stereo equipment.
75 ohm coax, 0.5 to 1 V signal level
But inside a computer, when they mention SPDIF, it may not
always be the 0.5 to 1V kind.
"Note on HDR-2 (2 pin header) interface used in some PC products:
Many modern PC CD-ROM drives and some soundcards (SB32, AWE32, etc.)
have a two pin digital output connector in the back of the drive and
they sometimes call that interface S/PDIF. Unfortunately the
electrical signal which comes from it is not exactly what is
described in S/PDIF specifications. The data format is exactly
the same, but the signal is TTL level (5Vpp) signal instead of
the normal 1Vpp signal. The output level might be selected to
make the interfacing to other digital electronics easy when
signal is travelling inside the computer (the normal output
driver system and input amplifiers can be avoided). The
downside of this is that you need to build some electronics
to make the signal from the CD-ROM drive to match what normal
S/PDIF equipments expect."
If you do want to try that, then the interface you choose inside
the computer may be context sensitive. To give an example,
I have a computer with an SPDIF input mounted inside the computer.
That input connects to an adapter plate with TOSLINK TX and RX
modules. Since the TOSLINK are TTL level devices, I know the
resulting SPDIF interface on the motherboard is the TTL kind.
Thus, I'd take a chance on connecting the 2-pin on the back
of the CDROM, to the multiple pin header on the motherboard.
If, on the other hand, the motherboard header goes to an RCA
jack on a PCI adapter plate, I'd suspect that was 0.5 to 1 volt
level. The adapter plate or module, gives a hint as to what
kind of interface is available inside the computer.
In any case, be absolutely sure on the 2-pin, you know which
pin is signal, and which pin is ground. Grounding the signal
pin by accident won't make the CDROM drive very happy.
I can think of three ways to get music off a CD.
1) Use the four pin analog audio cable, run from CDROM to
motherboard header or to the sound card CD header. If the
drive is external, run a stereo audio cable to the Line In
on the back of the computer.
2) Use the 2-pin SPDIF, assuming you've figured out whether
your computer has a working SPDIF input. Find a TTL compatible
SPDIF input, rather than the standard low level 0.5V 75 ohm
3) Install the CDROM inside the computer, connecting it to
the IDE ribbon cable. Enable DAE in Windows, which allows
the music CD to be played, by reading the music data right
off the CD. This dialog can be found in Device Manager,
for the CDROM entry (under "DVD/CD-ROM drives").
When you do that, you no longer need the four pin audio cable
mentioned in (1).
"Ripping" a CD, involves the same kind of thing. In simple
music playback, the CD player rotates at 1X speed. "Ripping"
a CD, implies reading the CD at a much higher speed, like
copying a data CD.
When an optical drive doesn't support "ripping" at high speed,
the drive is described as suffering from "riplock". This is
unimportant if all you want to do is play a music CD, since
the drive will spin at 1X just fine.
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