dac for 5.1

Hi everybody.

I have build 5 chip amps with the lm3886 and i use them for musice, movies with my pc with a sound card that has a 5..1 decoder on it for dolby digital.The sound and amount of power is good for the room and for my ears BUT i have analog connections beetwin the power amplifiers and the sound card.I would like to have a dac with a nice coaxial cable insted of all the analog cable connections.Is this possible for a new project?Can someone point me to a easy none expensive dac to build?

Thanks alot George
 

GestaltH

Member
2008-01-21 6:44 pm
Hi,

I had been interested in doing something similar. I would also like to hear any information on this. The idea that I had come up with is posted here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=116779

I don't know if that helps at all, but maybe it'll give you some ideas. The basic idea that I'm currently thinking about is modifying a current sound card to intercept the I2S output at the DAC. I can then use this output for my own DACs. Unfortunately I don't have any info on the actual DAC design.

Good luck, and let me know if you come up with a solution.
 
Hi

Some time ago I was reading through some threads on a DIY dolby digital processor and it seemed that it can't be done. DD format is legally protected, consequently one can't obtain the decoder chip and/or the algorithm. What has been suggested at the time was to modify an existing processor, that is, take the analog out's of the processor/dac and route them through whatever one fancy is best (trafo's, opamps, valves).

But things may have changed, and nowadays it may be possible to build a DD decoded from scratch. Let's see if some of the pro's has got something to say on the matter.

Erik
 
Hi

i think that i dont need a dolby digital processor since my sound card has one on it (x-fi sound blaster).I just need a 5 chanel dac to connect the dac with spdif cards out and then if posible decod DD from the sound card.
I can decode now from the sound card with analog connections(rca) but i would like to get rid of all the rca connections from eatch chanel and have one nice cable from spdif out to my dac for 6 chanel amp.
Maybe someone can help if this is possible and point me to a nice and not complicated dac to build.

Thanks George
 

GestaltH

Member
2008-01-21 6:44 pm
Hi again,

This was my idea to begin with also. I made a post about it here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=116337

The problem that I came up with with using the SPDIF output was that only 2 channels are sent through the SPDIF interface in uncompressed format. If you want 5.1 or 7.1 it appears that the only way to get that from SPDIF is to use Dolby Digital pass through. You then have the problem of decoding that. This is why I switched to the more complicated solution that I mentioned earlier.

Please post your results if you find some simpler way to accomplish this. Or if you find that my conclusion was false for that matter. I never had it verified by anyone more knowledgeable, but the articles appear to be saying this.
 

GestaltH

Member
2008-01-21 6:44 pm
I just thought I would add that the x-fi cards use the Cirrus CS4382 DAC.

http://en.wikipedia.org/wiki/Sound_Blaster_X-Fi
http://www.cirrus.com/en/pubs/proDatasheet/CS4382_F1.pdf

The pin pitch is 0.5mm. It also uses left justified, right justified, and I2S formats. There should be a way to intercept this for use in your own DACs. I complicated my design by wanting speaker and room correction, as well as wanting a digital signal all the way up to the speaker. It sounds like what you want to do would be easier than that.