DIY 5.1 decoder

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I just priced a McIntosh 5.1 decoder. It goes for $2500.

So, does anyone have information on how to construct one myself?

Either where to buy a chip OR the dolby digital protocol and I can burn my own PLA. That, of course, would be far more fun.

Any suggestions about the overall structure of the decoder. I'm assuming it will also need a pre-amp section. Maybe 5-6 Bride of Zen's?

I e-mailed those people. They want to sell me 1000 per year!

I'm trying to con them into selling me a board configured for another customer that is in production right now.

Those boards are awesome! 0.005% THD, digital 5.1 and DTS.

I want one! Thier startup price is $300 then $105/unit at 1K/year.

I'm hoping I can talk them into the $300 for just one.

Licensing of DD

One of the walls you may also hit, is that unless you get the specs, board developers are going to want to know if you are a licensed developer of DD, DTS and/or THX. All require a license to sell products for, and the companies want to see it before they'll sell you a board. (Forget about getting a personal license, what I've seen is that they're outrageously expensive)

If all you want to do is DD 5.1 and don't care about DTS or THX, you can go check out some HDTV pages. I know somewhere the main HDTV governing body has the AC5.1 spec listed out complete with the calculations and bitstream formats. It is (at least used to be) freely downloadable as a PDF file. Unfortunately, I threw out my copy just recently and am right now trying desparately to remember the group that has the spec. (A search on AC5.1 should turn it up)

I took a look at the page posted and basically what they've done is taken one of the Motorola DSP chips and put it in a slight variation of Motorola's development board. (Although at an apparently lower price point) You might run into the same problems with the DSP chip as you will with the board re: the licensing issue.

If you do have luck in securing a board or chip, let me know, I've been interested in either building a decoder or getting one.
Dolby Digital Decoder

Promitheus, I have a Marantz DP-870 dolby decoder that I picked up used for about $250. You can find used equipment at Audio Review and AudioGon. One drawback to the Marantz unit if you don't already have a Marantz Pre/Pro is that it does not come with a remote control. This isn't a problem for me, but it might be for others, depending upon how it is installed (ie: either between the preamp and amps, or plugged into the 6-channel input on a receiver/preamp).

For my senior EE design project my partner and I made a surround sound decoder. We used the Crystal CS49326 DSP which is in the home theater chipset line. We were able to license the Dolby Digital application code under an educational agreement but didn't have any luck with DTS. We used a Crystal CS8414 line receiver and CS4340 DACs and laid them out on a 4 layer board.

I am new to the whole DIY realm (this project turned me on to it) and consequently the HW for the project probably isn't very optimal and needs a board revision. However the board works and we finished the entire thing in a semester(~14 weeks).

Our design is online and has the code (sans the AC3 app code), schematics, and a picture of the board with 4 of the 6 channels populated on one of our boards.

Check it out <a href=>here</a>

I guess if you knew what you were doing with a DSP chip and had the decoding algorithms for whatever formats you wanted it would be do-able.

The hardest part would be getting hold of the algorithms especially if you wanted the latest such as DTS 24/96.
It sure would be a great project.

kev31mc - you're link doesn't work, I'd like to see it.
Extigy -- and then break the warranty

How about getting into a SoundBlaster Extigy at about $150 or less. Then you can break the warranty and start putting decent D/A's in there.

Another alternative is to use one of the commercial Windows DVD players that support decoding + send the signals to whichever ports you have available.

Yet another alternative is to purchase say one of the higher end Sony processors and modify it. They contain lots of kit + DSP's etc. Now that I am thinking about it again, perhaps one of the cheapes surround sound receivers would be even better, just clean out all the amps etc. so you have room for modification.

Wow! Talk about luck. This is the exact subject I logged on for. I'm really looking for a DIY 5.1 decoder/preamp but can go with one of each. Looks like the most feasible way is buy a used decoder then build/find a 5.1 preamp. But I have seen used all-in-one's on the net from reasonably reliable sources. Problem was they were discontinued models. Still waiting for the spec shets from the original builders to be sure they have the right features.
This topic has gone a bit stale, but the only open DD decoder that I'm aware of is at AC3 only, and reports on quality aren't the most encouraging, but at least it's an implementation that you can look at and play with. Mostly targeted at Linux DVD players, but should be relatively portable.

If you can get any boards/chips then it's obviously a great way to go, but I wouldn't hold out much hope. Any legit manufacturer will likely clam up if you aren't a Dolby licencee.
Has anyone talked to Dolby about licensing? They have info available on their site, and since at least one college project recieved a gratis license it seems within the realm of possibility that they would grant a license for "educational" purposes.

After all, I doubt anyone here is looking to develop a commercial decoder.
i think that s what i will do, build a hi end dac (2channel) 5.1 pre-amp (with 6 bosoz of course!) complete with 6 boards of relays and resistors for volume and then get a hi end player which has audio outs. that way u can switch between the audio ins (5 channel) from DVD or computer or whatever, or the digital ins (2 channel) for CD, TV and MD.

Complete 5.1 channel sound from signle ended design, nice, but big!
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