Need help setting up z906 speakers to my soundcard

[sohaibrazzaq]

Hi all, i just bought new speakers (Logitech z906) and hooked them up via analog connectors (as i always do).
Everything working fine but i figured out that in order for them to decode DTS properly i need to setup a digital connection.

So i googled and i am overwhelmed by so many different terminologies. Spdif/coaxial/optical that my head literally became swinging for a sec. Truth be told i never setup a home theater system myself and i don't need anything fancy, i am just trying to figure out how to connect the speakers to my sound card via digital connection, i.e. what kind of cable i really need to buy.

My sound card is Creative X-Fi Titanium (SB0880) and speakers are Logitech Z906. I even googled some visual pics but yeah i am still too dumb to figure out what kind of cable i really need. If some audiophiles can explain a bit or just lemme know which cable to order then i would be really thankful.

Here have a look at following two diagrams to know what connectors my card and speakers got:

Soundcard:
http://support.creative.com/kb/ShowArticle.aspx?sid=68106

Speakers:
http://support.logitech.com/en_ch/article/23022?product=a0qi00000069uqEAAQ

[jagabo]

Both your sound card and speakers have optical SPDIF connectors. You just need an optical cable like this:

https://www.amazon.com/AmazonBasics-Digital-Optical-Audio-Toslink/dp/B00NH11H38/

But you should be able to install a DTS decoder for use with your current analog setup.

[sohaibrazzaq]

Thanks jagabo for the valuable input. I am gonna go out to my nearest retail store tommorow and pick up the cable. It sucks logitech didn't bother to include a $5 cable in $300+ speaker set.

As comparison, i recently bought an Asus 4K monitor and it came with a DisplayPort 1.2 cable & 2x HDMI 2.0 cable (Yes 2 HDMI 2.0 cables). Gotta love Asus.

[sohaibrazzaq]

Update: So i picked up a cheap ~$5 optical audio cable and hooked it to my amp and i can immediately notice the sound quality is much MUCH inferior to analog.
Is it because of the cheap cable? The store i went to had a good branded energizer optical cable for $35 and the cheap $5 which i bought. Is the price difference make much difference? I can't really order online since i live in a 3rd world Asian country.

Also on my logitech display, the DTS decode led never lights up even if i am playing a source which has DD or DTS surround. In windows SPDIF output format i only have the option to output in 2 channel. Its currently set to 2 channel, 24bit, 48000 Hz

EDIT: A little progres. I can output surround if i hook the optical out of my motherboard rather then soundcard. It appears my old X-Fi Titanium only does 2 channel over spdif. However the sound quality is still atleast 10 times better over analog and the issue is out of these two i think:

1. Either the optical audio cable i bought is total trash which is causing poor quality.

2. The DAC of my soundcard is FAR better then what my amp can output. Because as far as i know, for analog signal your soundcard's dac does the digital-->analog conversion and then passes the signal to amp. In digital format, the signal is passed as is to the amp which does the rest.

[jagabo]

In what way is the sound inferior with the optical cable? In any case, the cable is almost certainly not the problem. Errors in digital audio transmissions are not subtle -- you will hear loud clicks, pops, screeches, etc. I also doubt the DAC is the issue. Digital to analog audio conversion is pretty trivial. It's more likely the X-Fi was applying some kind of processing that you liked.

[sohaibrazzaq]

Like at same level the sound on analog is MUCH more loud and clear, it has more range in lows and highs.
I dunno either its that or that my ears have over 10 years of experience with listening sounds coming with few creative effects like X-Fi crystallizer etc in the mix but even if i disable all of the creative enhancements the sound coming out of speakers is much more loud and crisp.

[jagabo]

Loudness is not quality. Crispness is probably just an equalization curve being applied by the X-Fi. Passing digital audio from the source to the speakers bypasses all that processing. And crispness also doesn't equate to quality. A professionally mastered source and good speakers don't need to have the highs boosted -- except maybe to make up for room acoustics.

In any case, a bad optical cable could not cause those problems.