TOSLINK/Sound Card question

**hartigan** · 06-23-2009, 08:54 PM

I'm wondering what signal is carried by a TOSLINK cable.

Is the DA processing done before the signal is sent down the cable or after?

The reason I ask is because some people purchase high-end sound cards with 24-bit DA converters and such. Is there any fidelity benefit to that type of hardware if using a TOSLINK cable from the on-board audio/sound card to the amplifier?

I'm planning on running a TOSLINK cable directly from the back of my Zotac IONITX-A-U (Uses a Realtek Azalea ALC622 5.1HD) into my Zapco DSP6-SL. If the Zotac is just sending the unprocessed digital bitstream over TOSLINK and the DA conversion is happening on my Zapco DSP, I don't see any need for a high end audio solution on the CarPC side of things. I'm assuming that the Zapco does this processing.

Am I taking crazy pills or am I right in what I'm thinking?

**soundman98** · 06-24-2009, 12:39 PM

I believe you are on the right track.

i havent ever used any of those parts(or toslink for that matter), so i can't be positive, but the biggest advantage to toslink in the car is that you wont' get any induced noise between the 2 units.

I think there is some processing done before the toslink output though- like vol, and eq.

technically, a separate audio card will be better (a separate, dedicated processor), but in most sound systems, I doubt you will be able to hear a difference in the end result.

**efun** · 07-09-2009, 05:32 AM

Originally Posted by hartigan

Is the DA processing done before the signal is sent down the cable or after?

NO DA processing before the signal is sent. Take the CD audio for example, the signal itself is digital, no need convert to analog before send via TSOLINK

Originally Posted by hartigan

The reason I ask is because some people purchase high-end sound cards with 24-bit DA converters and such. Is there any fidelity benefit to that type of hardware if using a TOSLINK cable from the on-board audio/sound card to the amplifier?

high-end sound cards with 24-bit DA converters is for it's analog output

I'm planning on running a TOSLINK cable directly from the back of my Zotac IONITX-A-U (Uses a Realtek Azalea ALC622 5.1HD) into my Zapco DSP6-SL. If the Zotac is just sending the unprocessed digital bitstream over TOSLINK and the DA conversion is happening on my Zapco DSP, I don't see any need for a high end audio solution on the CarPC side of things. I'm assuming that the Zapco does this processing.

It seems that the high end sound card has more advanced function to process digital signal. One of them is "improve sample rate", for example, improve CD 44.1KHZ to 96KHZ. Another important point is high end sound card can hanle "Jitter" better. Note that Jitter is the killer in digital audio.

I have another question: if play mp3 on PC, what signal will be sent via TSOLINK? mp3 stream or uncompressed PCM stream? if is the latter, who decode the mp3 stream? the player software or the sound card?