Go Back   Home > Forums > >

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Does it exist: Dolby Digital Decoder Chip Or Board?
Does it exist: Dolby Digital Decoder Chip Or Board?
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools
Old 9th March 2007, 10:24 PM   #1
6f6 is offline 6f6  United States
diyAudio Member
 
Join Date: Nov 2006
Question Does it exist: Dolby Digital Decoder Chip Or Board?

Hi Folks,
For my own part, I like to listen to music on two channel equipment of my own design. However, in the future I would like to undertake building a home theater set-up for a friend of mine. My objective is to create a Dolby Digital (AC-3) preamp which uses 6sn7 tubes in the voltage amplification stages as I love their sound in my homebrew preamp. My problem: how to get an analogue signal to feed the 6sn7s.
My Questions:
1. Does there exist a circuit board (or just a chip) which will allow me to apply the digital signal from a dvd player and some B+ and get an analoge signal?
2. If so, where does one purchase said item?
  Reply With Quote
Old 10th March 2007, 12:01 AM   #2
Fenris is offline Fenris  United States
diyAudio Member
 
Join Date: Jun 2004
Location: The last frontier
Well, there are two problems to overcome here:

1. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.

2. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.

While technically this is only one problem, it's such a big one that I thought I would mention it twice. A work around would be to find a stand-alone decoder (I found one on e-bay two years ago for about $100), take it apart, trace out the analog signal runs to where they originate, and take the signal from there into your pre-amp, bypassing the probably low quality analog output sections. I did something similar with an older Sony integrated amp that didn't have pre-outs. I just traced the lines and added RCA jacks on the back to work with a friend's power amp.
__________________
"if Im going to have something done poorly, Id rather not be paying professional wages to someone to do it." -anchorman
  Reply With Quote
Old 10th March 2007, 01:14 AM   #3
Drew Eckhardt is offline Drew Eckhardt  United States
diyAudio Member
 
Join Date: Jun 2003
Location: Menlo Park, CA
Note that free software libraries exist for both AC-3 and DTS decoding. While selling a commercial product based on them might get you in trouble, the software is suitable for personal use. So if you really wanted you could build a digital preamp arround a small passively cooled (Via C3 out to 1GHz) single board Linux computer with software on compact flash.

PC104+ boards are available for pretty much every purpose; you can get things like S/PDIF in for your DVD player. S/PDIF in+out to USB adapters are available too.

Boot times on the order of single-digit seconds are possible with the right system, which beats my Lexicon from a hard power cycle.

Use the DACs, current to voltage conversion (resistor with tube buffer), etc. of your choice. Or just use a mainboard with 5.1 analog outputs.
  Reply With Quote
Old 10th March 2007, 03:33 PM   #4
theAnonymous1 is offline theAnonymous1  United States
diyAudio Member
 
theAnonymous1's Avatar
 
Join Date: Feb 2004
Location: Anonymityville
Get it while it's hot! Only 5 hours to go.

http://cgi.ebay.com/Klipsch-ProMedia...QQcmdZViewItem

You could easily add your tube output in place of the solid state.

I have a few DSP boards from some motorola HT receivers that have CS493263 decoder chips. The chips could be removed and used for a new project, but it would be a heck of a lot of work. Definitely more complicated than just spdif in, 5.1 channel out.

Here is a pic of the DSP board. If you want them their yours.

http://i13.tinypic.com/2cdaf6b.jpg
  Reply With Quote
Old 12th March 2007, 10:00 PM   #5
6f6 is offline 6f6  United States
diyAudio Member
 
Join Date: Nov 2006
Anonymous1,
The board you have pictured seems like it would do the trick depending on the actual output level at the terminals. If it is not too high, I could probably do a direct-coupled 6sn7 gain stage/cathode follower. One question: would the input be the terminal labeled "AR"? Would this connect to the single digital audio output on the back of the DVD plaver?

6f6
  Reply With Quote
Old 12th March 2007, 11:26 PM   #6
Nisbeth is offline Nisbeth  Denmark
diyAudio Member
 
Nisbeth's Avatar
 
Join Date: Jan 2001
Location: Denmark
Does it exist: Dolby Digital Decoder Chip Or Board?
AR and AL are the analogue inputs and the chip next to the AA-label (lower left) is an ADC. The digital inputs are on the white connector on the right edge of the board and they feed into the selector/MUX on the CS8415 (digital receiver).


/U.

PS: Anonymous1, YGM!
  Reply With Quote
Old 13th March 2007, 01:14 AM   #7
6f6 is offline 6f6  United States
diyAudio Member
 
Join Date: Nov 2006
Nisbeth,
Thank you for that information. I ask this question:
Can I get all 5.1 channels of output by connecting the Right and Left RCA jacks from the DVD player into AR and AL?
  Reply With Quote
Old 15th March 2007, 12:05 AM   #8
dangus is offline dangus  Canada
diyAudio Member
 
Join Date: May 2004
Location: Vancouver Island
The price for that Klipsch box seems a little steep. You can buy a complete receiver for that money.

The Technics SH-AC300 and SH-AC500D aren't bad, and don't fetch as much on eBay. But, there's no EQ, the sub crossover frequency is fixed, only the 500D does DTS, and in DTS mode there's no "bass management" or phantom center support.

There's a Pioneer receiver that inexplicably has preamp outputs, the VSX816-K. It can be had for well under $300 US. http://reviews.digitaltrends.com/review3629.html
  Reply to this post

Reply


Does it exist: Dolby Digital Decoder Chip Or Board?Hide this!Advertise here!
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Dolby Decoder hop_305 Digital Source 4 8th August 2004 12:34 AM
With a 5.1 sound card, do I still need a Dolby Digital decoder? JCoffey Digital Source 14 30th April 2004 03:10 PM
about Dolby 5.1 decoder Corsairr Digital Source 7 22nd December 2003 01:51 AM
Dolby Digital / DTS decoder DIY link nFORCE Digital Source 6 22nd September 2003 05:19 PM
Standalone Dolby Digital & DTS Decoder Neopsp Everything Else 2 4th May 2002 12:49 AM


New To Site? Need Help?

All times are GMT. The time now is 08:06 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki