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spdif decoder

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Thunderchild

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I am sure that we are all aware of the serial audio outpèuts found on most audio cards that from one coaxil socket play all six xhannels of a film. is there a standalone decoder diagram or intregated circuit that can give me the 6 signals from the coaxil out put ? I hate to spend all that money on the speackers with the right input as the prices are more than I think they should be. it's not like it's militery technology probably a very simple protocol. plus it means I can use any speckers i wish without paying for the whole decoder again.
thanks
 
whats wrong with using the decoding hardware built into the card?

most cards with the digital sp/dif output, also have the analog version of all those channels.

there's probably a single chip solution to do this, but getting one is going to be a challenge

you need to convert a single digital signal into six (or more) analog signals.
 
well first the six channels need to be extracted then converted to analog problem is the timing ecc. I need the specs but i think there must be one chip that does it all and give the 6 out puts. producers most certainly make complex descrete circuits there are probably just a few chips around that do it all
 
Thunderchild said:
well first the six channels need to be extracted then converted to analog problem is the timing ecc. I need the specs but i think there must be one chip that does it all and give the 6 out puts. producers most certainly make complex descrete circuits there are probably just a few chips around that do it all

Except you probably can't buy the chips, and you also need to know how to set them up - presumably via a data bus of some kind.

Just buy one! - they are cheap enough!.
 
hasn't anybody ever opened up a coaxil decoder system ? someone must know whats in there i mean we are only talking about the speakers doubling in price the tech can't be that great just rarely used.
 
maybe you can share some details about your application.

I don't think you'll be able to build a digital decoder as cheaply as Creative Labs, which is packaged with every sound card they sell these days, not to mention the nock-off's and clones that are even less expensive. do you want to decode a s/pdif signal, that is not coming from a computer? for example you have a stand alone dvd player with only digital outputs, and you want to connect analog speakers?

I found a simple circuit here that decodes the main left and right channels:

**broken link removed**

perhaps that can be used as a building block to extract all six (or more) channels.

I think the jist of what you need is something to demultiplex (not the correct term) the individual channels from the single PCM bitstream (most of the time s/pdif is in pcm I think), and pass the individual bitstreams onto a multichannel DAC, and then from the DAC to a preamp, and then you've got analog

check out Cirrus Logic: www.cirrus.com

they have the chips that do just that... specifically the CS42516 ... it includes an 8 channel SPDIF receiver / decoder and six DACs - The reasoning here (i believe?) is your source could have a prologic stereo audio stream as channels 1 and 2, and have channels 3 through 8 as the dolby digital surround sound bitstream, the chip also has digital volume control and two onboard ADCs. Looks like the chip is controlled via I2C, so any suitable microcontroller should handle it. There is also what appears to be a digital output of some sorts. The chip only comes as a 64 pin flatpack - so you'll need a prototyping adapter or some PCB fab skills to work with it.
 
perfect thank you that is the info it is pcm outpout and yes demultiplexing is all i think is needed. i think basically it is this: demultiplex the chanels and then convert them from digital to analog or convert from digi to ana and then demultiplex my problem is the timings and how the decoder knows what is comming when.

i'll check the link out thanks
 
as I recall, there's a procedure called clock recovery or something ... that chip has a module internally to perform the function, although I'm sure its possible a multitude of different ways.

I recall reading somewhere spdif is a two's compliment binary datastream, if that is any help
 
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