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-   -   DIY 5.1 decoder (http://www.diyaudio.com/forums/digital-source/62-diy-5-1-decoder.html)

pixie 26th January 2001 09:29 PM

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?

Thanks,
pixie

JoeM 27th January 2001 03:39 AM

I too have just started looking into this. You might want to check out the products on this site.
http://www.samplerate.com/products.htm


promitheus 28th January 2001 04:38 PM

Thatīs a great idea but there isnīt much to find on this subject.
I will check the site from JoeM.
JoeM thanks.

pixie 29th January 2001 05:37 PM

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.

Later,
pixie

Schaef 29th January 2001 07:36 PM

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.

ebrewste 30th January 2001 03:59 PM

If you are investigating DTS chips, add the Crystal CS4928 to the list. If anyone gets around the licencing issue, any chip will do. I've been itching to get a Rotel rsp-976 and pull the CS4928, but I suppose $1200 for a chip isn't so economical.

tpb 2nd February 2001 02:08 AM

DIY ac-3 / DD5.1 specs
 
http://www.dolby.com/tech/desgnac3.pdf
They have some brief info on what you're looking for. I havn't had alot of time to look it over.
Hope it helps.
ttyl
tpb (lurking)

tpb 2nd February 2001 02:24 AM

More DIY 5.1 decoding
 
I was also able to dig this up. Looks like the complete spec.
http://strategis.ic.gc.ca/pics/sf/a_52.pdf

enjoy
ttyl
tpb (still lurking, I swear)

Schaef 7th February 2001 04:52 PM

Yup
 
That appears to be one version of the spec. I took a quick look through about half of it and describes the breakdown of the bitstream, so using that it should be possible to code a decoder from it.

promitheus 7th February 2001 10:49 PM

Thanks for the links guys.
It would be very cool to make a digital decoder.
btw. what is a good decoder to buy ?


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