Thread: For those who want true 5.1 Dolby Digital and DTS

I wanted to try to contribute an all in one thread that explains how I was able to achieve Dolby Digital, DTS and Pro Logic from my computer in my car. I hope this helps someone and gives people ideas and saves countless hours of product sourcing.

This is my hardware:
Lilliput 7" VGA
512mb RAM
VIA EPIA M10000 link
Opus 90w PSU
80g WD SE
40g laptop drive
Slimline Slot Load CDRW/DVD link
Bixnet.com Slimline to USB 2.0 bridge link
Panasonic CY-AC300EX Digital Surround Processor link

To achieve 5.1 Dolby Digital and DTS you have two roads to take. You can either get an external processor and use your onboard soundcard (if your motherboard offers S/PDIF out like the Via M10000) or you can get an external soundcard that has 5.1 out and Dolby digital. There are pro's and cons to both. Below they are listed

External DSP Pro's
1. You can achieve Dolby Digital, DTS over Six chanels (5.1)
2. You usually have a controll unit (Head Unit) for external volume control
3. This is really the only option if you want DTS processing
4. No extra load on your CPU
5. No USB bandwidth monopolization
6. Allows the opportunity to have a nearly digital system with the addition of a digital amp.

External DSP Cons
1. Usually Expensive. I paid 330 for mine but they can be bought refurbished for less.
2. You have to control the volume (if using the optical input) with an external control unit which may be undesirable if you want to control the gain on the digital output

USB Sound Card Pro's
1. Cheap
2. Less complicated and less wiring
3. Control 5.1 Dolby gain with computer

USB Sound Card Cons
1. Utilizes CPU to process and decode the surround sound
2. Utilizes USB bandwidth which can produce choppy DVD playback if you have other heavyweight USB accessories
3. No DTS processing


You can see why I chose to go with the external surround sound processor. I wanted True 5.1 and with my hardware I didn’t want to intrude on my USB bandwidth and CPU power. This may be of no concern if you have a PIIII and are using a FireWire or IDE DVD drive however even in that case you still don’t get DTS processing. If you are on a tight budget and don’t care about DTS processing and are using some hardcore hardware then by all means go for the Audigy or Extigy by Creative. Otherwise the external Digital Surround Processor is the way to go.

The Configuration:
My Onboard soundcard had a Coax S/PDIF output and the CY-AC300EX had an Optical S/PDIF Toslink input so a converter had to be installed. I used this one: http://store.yahoo.com/trianglecables-site/pof-830.html. So I ran the Digital out from the computer into the Digital in into the DSP. From there the DSP decoded the dolby codec and split the signal into 6 speretate channels. Each channel needs to be amplified except the center channel (on this particular DSP it has a built in amplifier for the center channel only) so from the DSP I ran each channel to an amplifier. I used a 4 channel 400w amp for the Front and Back Left and Right speakers. The center channel is already amplified (30w) and I ran the Rear channel to a separate mono amp. Check out the attached picture for a diagram

I used a Monster Coax Digital Cable link and a Phenoex Gold Toslink cable link for all of my cabeling.

Software Setup:
I followed this guide for the EPIA http://mini-itx.com/hardware/ac3/. I think the process should be similar for any other motherboard or sound card that has S/PDIF out. Use this as only a guide if you have another motherboard. The main thing i think is to find and enable your digital output (coax/optical/ttl) and install the AC3 Codec.

After you install the AC3 Codec and set it up as it says to in the guide then make sure that your DVD player is set up to output Dolby Digital over S/PDIF. I used WinDVD and was supprised after i had everything setup that i wasn't getting Dolby Digital. I found out after some tweaking that there is a settings page that had the audio set to ANALOG. After I switched it to Digital everything worked fine.

After you follow all of the above decisions and steps you should be good to go.

A Couple things to Note:
Not all DSP’s are created equal. Keep in mind when purchasing your DSP that the Mass majority have Proprietary optical cables and Proprietary protocols making it impossible to hook up to the computer. They are mainly made so you buy the complete system from them. I bought the Pioneer DSP and later realized that it A) needs a control unit and can’t act as a standalone unit and B) the optical input was proprietary.

What you are looking for is TOSLINK Optical input that support S/PDIF which the CY-AC300 does. I hear that the Alpine PXA-H510 works for this as well but I have not tested it.