how do i connect my soundcard to my receiver/AC-3 decoder?

[Yoshi]

OK guys here is the damn deal...

First SPDIF is not a type of connector or cable, it a simply an interface for transmission of digital data (IEC-958).

I have seen several sound cards that have a digital out mini-jack on the back. It is safe to assume that this jack uses the SPDIF interface since it is the only digital data interface used for digital audio data on comsumer level products. To connect to a digital ready receiver you will need a mini-jack to RCA connector adapter and a 75 Ohm coaxial cable with RCA type connectors. Once set up you will be able to transmit any sort of audio standard that is implemented in the software be it standard PCM, Dolby Digital, or DTS (I have already noted a few video games with the Dolby Digital logo on the box). Most digital receivers do a damn fine job of taking standard PCM and decoding it into Dolby Pro Logic signals, it will make your video games sweet.

One other thing to keep in mind...Hopefully your sound card's digital output is set up for a 1 volt output signal. Other PC components such as CDROM drives which include 2 pin SPDIF outputs only use a 0.5 volt signal which is fine inside the computer, but is not typically strong enough to travel through a patch cable to a receiver.

There is my 2 cents!

 

[Pariah]

THX is not a surround sound format, it is a certification. Dolby prologic, Dolby Digital, DTS, and other formats can all be THX certified.

This is pulled from the Klipsh press release about their Promedia's:

"Klipsch, L.L.C., a leading manufacturer of loudspeakers for professional and home entertainment applications, has joined with Compaq Computer, the leading PC manufacturer, to introduce the first THX® Certified speaker system for multimedia applications."

THX is basically an ego trip for George Lucas to show everyone how powerful he is.

 

[Yoshi]

Correct THX is a set of specifications for amplifiers and speakers, not a surround sound format.

I would not exactly say that George Lucas was on an ego trip, he is just setting the standard and brining some order to the system.

 

[Floydian]

Here is my understanding (I'm pretty sure its right, but not sure)
SP/DIF is a method of transfering digital sound
AC3 is also
Digital OUT's can output both
The digital in's on cards coming from a cdrom/dvdrom can carry both also, so can recieve both AC3 and SP/dif signals.
I think what someone in this thread was trying to say is that if you output SP/DIF into your digital speakers, you only get stereo (front) surrond, which is true. You would need front and rear sp/dif outs for dual stereo surrond in a 4 speaker set up (this is available on some Live! daughterboards someone was talking about).
However, digital stuff encoded in AC3 carries 6 channels of sound, otherwise known as Dolby Digital 5.1, so this extra rear digital is not needed when playing dvds.

I think some digital speakers might double the sp/dif signal for the rear speakers, but I don't have any to know this for sure.
I believe this is why Creative labs adopted the proprietary DIN for some of their speakers - it can carry rear outputs - unlike the sp/dif interface.
I hope I got all that right.. heh


As for the cable - if you have a Live! with the digital out, use a "male" mono mini-plug to "female" mono-RCA to plug into the female(meaning hole) digital out on the live. Then just plug in any RCA cable from this to your AC-3 decoder.

With the Santa Cruz, it uses both the left and the right parts of an RCA cable to ouput digital sound. One side is AC-3 data only, and the other is SP/DIF. You'd have to use a stereo miniplug to stereo (the red and white) rca jacks. I'm not sure which side is which, so you would have to check on that.

Optical can carry both sp/dif and ac-3, depends on what you're playing. Plug in a TOSLINK optical plug (the square looking side) into your soundcard, and then plug the other end into the most likely TOSLINK on your decoder. There's a miniplug optical interface also (not to be confused with the miniplug on headphones), seen on many portable Mini Disc players, which is why they have to call it TOSLINK and not just optical.

Radioshack has the miniplug->rca adapter, just go in and ask for it, they'll know what it is.
Any RCA cable will do, just one plug on each end (male on both ends). Optical
I hope I have that all right, please correct me if I'm wrong.

 

[Yoshi]

Floydian,

You have a few true statements in you collection of thoughts, but again...

1. The digital output on your sound card will send PCM (stereo), AC3 (Dolby Digital), or DTS depending on what your DVD or gaming software support. All this happens over a digital interface following the SPDIF specification.

2. YOU CANNOT use a STANDARD RCA cable. YOU MUST USE A 75 Ohm digital coaxial cable.

 

[Hossenfeffer]

Scenario... I plug a coaxial cable into the coaxial digital out on the Live daughter card... the cable branches to RCA output(s) which I plug into the Phono inputs on the receiver (coax input is taken at the moment). Am I a crazy nutball? Heh.

 

[Noriaki]

Yoshi: You need a special Coax cable for SPDIF? Hmm me and pete just striped a red/black pair in half and used one of those...guess we got lucky His dual stereo RCAs were pretty high quality though.

 

[Yoshi]

I partially retract my statment about the cable. For a short run (a couple of feet) any coaxial cable will probably work. Using the proper 75 ohm cable will insure proper transmission of data without loss. Data loss will cause degration of the sound and possible improper steering of sounds when using a surround sound processor.

Also, you must use a digital input on your receiver. The phono input will not work, please tell me you were joking.

 

[Noriaki]

lol!
no no we weren't using a phono input...

it was the proper SPDIF input and the SPDIF output from the DVD player.

We just used one half of a Stereo RCA pair to connect them, not a special 75Ohm cable.

It was only a 3 foot cable though so perhaps if it were longer it would need to be better (the DVD player and VCR are right on top of the reciver and we stole the VCR's stereo RCA cable and used one half between the DVD and reciever so it was short).

 

[Ender510]

THX and SDDS are both certifications. In order to be "THX Certified", a system must include componenets that are "THX Certified" as well as speakers. To basically put in simple terms, the entire system must be capable of reaching certain levels of frequency, must notably in the lower freqs, the bass levels.. there are also a specific number of speakers required and other such details that I can't recall off the top of my head. Sony's SDDS is a similar concept - both more of a marketing scheme than anything. The reason why Lucas made this THX certification was to create a consistency for all movie watchers whether it was in different theatres, homes, etc. so that people would hear the audio that was meant to be heard by the movie producers/makers. Now, this is different from Dolby Pro Logic, Dolby Digital = AC3 = 5.1, and DTS.

Quick question for you guys.. what does the abbrev. TOS stand for??

 

[NicColt]

Like I said, it's one of the most confusing and contraticting topics ever and will probably always be.