On Thu, Jul 30, 2009 at 04:53:25PM -0500, Matthew Woehlke wrote:
Doug Ledford wrote:
> Every system I build still keeps the analog signal cable between the
> CD/DVD and the soundcard. This doesn't help if I try to watch a movie
> as that signal has to be decoded and then played, but for audio CDs
> it is still a perfectly acceptable means of playing the music. So I'm
> not sure where this "CD in is obsolete" comes from. Even the
> motherboard I bought about 2 months ago still has a CD in port and
> the CD/DVD in that machine still has an analog output.
CD is digital and can be read in digital format by your CPU and sent in
digital to the sound device. This is lossless.
You want to:
(D->A) do the DAC in the CD drive
(A) toss that on an analog wire
(A/A->D->A) apply an analog volume adjustment (if you're lucky; you
might actually end up doing a ADC, digital volume adjustment, DAC)
(A/A->D) toss that on a different wire that might be digital
(A/D->A) hear it from your speakers
You could:
(D) read the CD digital data
(D) toss said data to the sound device (losslessly!)
(D/D->A) apply a digital volume adjustment (or maybe analog volume
adjustment after DAC)
(D/D->A) send that, maybe digitally, to your speakers
(A/D->A) hear it from your speakers
What exactly is better about the first scenario? At *best* you're moving
the analog signal across a longer run of wire (and one that is inside
your computer case with who-knows-what shielding picking up
who-knows-what interference). At worst you've tossed several analog
elements into a process that could have been digital from disc to
speaker cones.
Seriously... do I miss something?
That reading in the data digitally uses non trivial amounts of PCI and
CPU bandwidth. If I can't hear the difference between the two modes,
then that CPU usage is a total waste of resources. I have other things
I want my CPU to be doing.