Any chips out there can decode SPDIF without a DAC? - diyAudio
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Old 20th March 2008, 07:36 AM   #1
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Default Any chips out there can decode SPDIF without a DAC?

I know this would be a somewhat odd request...

I'm looking to build my own variation of a DAC.
The end goal is to have a computer connect to a black box (SPDIF,MADI?) to output multichannel (6-8 prefferably) audio digitally and have the box convert the serial data into parallel outputs in such a way that all 16-24 bits of all channels will each have it's own 0-5v digital output. (serial to parallel done by microcontroller, probably)

From there I would be able to drive LEDs or process the audio with a microcontroller (build/program my own dithering, upsampling, volume control and the like) or directly control some fets to recreate the audio as a DAC would but on a higher scale (wattage)

I'm am no audiophile, nor do I know how my system would sound if the parallel'd data was converted back into an analogue waveform. But I'm very good with a datasheet and a dream.

Thanks in advance for your input.
--AkkerKid
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Old 20th March 2008, 05:16 PM   #2
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Default I'm guessing...

My first thought is to find a chip (or set of chips) that can go from USB directly to 6-8 channels over I2S. Does anyone know of a chip that windows would be able to output to easily with this functionality? Once I have the 3-4 I2S outs, I can start de-multiplexing the data lines into the parallel data I'm looking for...

--AkkerKid
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Old 20th March 2008, 08:56 PM   #3
phofman is offline phofman  Czech Republic
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8 channels over USB would very likely require USB2.0. I do not know of any consumer USB DAC running on USB2.0.

How about using a PCI card, hooking some differential transport (LVDS etc.) to its I2S on-board pins and feeding the signal out of the box via one or two CAT5 cables, the shielded variant?

This is basically what the TG link does (plus some multiplexing as it can feed iirc 8 channels over one CAT5 cable).
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Old 21st March 2008, 05:26 AM   #4
Cliff45 is offline Cliff45  United States
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Hello-

From the reading subject of this post, maybe this will help you:

Look at the Crystal/Cirrus Logic chips like the CS84xx series transmitter/receivers for dealing with SPDIF and AES audio streams:

http://www.cirrus.com/en/products/pro/techs/T4.html


These Cirrus units will do output/input via the I2C and SPI bus, I think....

Also, a very high-speed USB to I2C development interface is available from Total Phase at a fair price:

Aardvark USB to I2C Host Adapter


Finally, if you're planning on doing MADI, you'll need to get a FPGA to do the heavy lifting for you. There's no chips that do MADI anymore, AMD made one called the TAXI that's been obsolete forever. From glancing the AES10-2003 paper (MADI specs), you'll need to implement a 4B5B encoder and a 125mbit serial NRZI transmitter inside to get this started....

Link to some MADI info: AES10-2003 Paper

Hope this helps!
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Old 21st March 2008, 11:23 AM   #5
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Quote:
Originally posted by Cliff45
These Cirrus units will do output/input via the I2C and SPI bus, I think....

Also, a very high-speed USB to I2C development interface is available from Total Phase at a fair price:

Aardvark USB to I2C Host Adapter
I2C gets you nowhere here, even for stereo. The Cirrus family have I2C control but audio is I2S. I2C isn't fast enough for stereo, nevermind multichannel. The Aardvark unit is thus of very limited use.

There are a few USB to SPDIF chips for stereo. Firewire is another way to go, look at

http://www.profusionplc.com/pro/gex/...ICEII-TCD2200K

I haven't tried these but the development overhead for Firewire is much higher than for USB.

James
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