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PCIe to I2S?


numlog

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Is PCIe to I2S really not possible yet? is there a reason other than cable length why USB and USB-to-I2S interfaces are used when DAC chips have I2S inputs?

 

There is the Pink Faun I2S interface and this apparently is a PCIe to USB to IS2 converter, which you could kind of suspect since there are no PCIe to I2S chips in existence.

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28 minutes ago, numlog said:

that would be the CM8888? it looks like the Pink Faun is using that chip too.

Is that converting to USB internally is the question. 

 

the block diagram for it shows PCIe > MCU > I2S, MCU could mean anything, maybe there is some more clues in datasheet as to whats happening but its too complicated for me

The chip is Intel HDA compatible. If there is a USB link somewhere inside the chip, that would be a most unusual design, and it would have to be invisible from the outside. The MCU block is a microcontroller that handles the high-level host interface and allows firmware customisation.

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1 hour ago, mansr said:

The chip is Intel HDA compatible. If there is a USB link somewhere inside the chip, that would be a most unusual design, and it would have to be invisible from the outside. The MCU block is a microcontroller that handles the high-level host interface and allows firmware customisation.

ok, thanks for the help. 

Based on a few forum posts It might be possible cheaply utilize this chip by finding a soundcard that uses it and fitting my DAC inside the PC to connect the I2S lines over a very short distance, maybe upgrade clock, use a better power supply.

 

I can see how for a lot people the Pink Fauns LVDS solution is very useful  as bringing your DAC that close to the PC is not going to be possible in most cases, like speaker systems, plus with the power supply option and use of high quality components its not a bad deal

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  • 2 weeks later...
On ‎2‎/‎10‎/‎2019 at 9:16 PM, numlog said:

Is PCIe to I2S really not possible yet? is there a reason other than cable length why USB and USB-to-I2S interfaces are used when DAC chips have I2S inputs?

 

There is the Pink Faun I2S interface and this apparently is a PCIe to USB to IS2 converter, which you could kind of suspect since there are no PCIe to I2S chips in existence.

We indeed use the c-media chip on the I2S card. The chip is PCIe directly to I2S. Nothing of USB is involved in the process. I2S or IIC stands for Inter-IC Sound and is an electrical serial bus interface that is used to communicate PCM audio data between integrated circuits. The I2S bus separates clock and serial data signals, resulting in simpler receivers than those required for asynchronous communications systems that need to recover from the data stream. A frequently heard criticism is that I2S is not suitable for use between two devices. This criticism is totally unsubstantial. Yes, we advice to use an I2S cable not longer than 1,5 to 2 meters, but that's fine in most situations. The results achieved with the Pink Faun I2S bridge speak for themselves. There’s a review of our Pink Faun streamer 2.16x in where the I2S is used linked to an Aqua Formula xHD DAC. You can read it here:
https://www.hifi-advice.com/blog/review/digital-reviews/music-server-reviews/pink-faun-2-16x-1-3/

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25 minutes ago, Pink Faun said:

A frequently heard criticism is that I2S is not suitable for use between two devices. This criticism is totally unsubstantial. Yes, we advice to use an I2S cable not longer than 1,5 to 2 meters, but that's fine in most situations.

Now you're talking about LVDS links, which means it's no longer I2S even if there is a direct mapping between the signals. Furthermore, most DAC chips require a master clock synchronous with the LR and bit clocks. The I2S specification does not, however, include this clock, and the required rate varies between DACs. That alone makes it unsuitable as an interoperable interface unless augmented with additional signals and requirements, but then it can no longer accurately be referred to as I2S. I see your interface includes an MCLK signal, so you must be making some assumptions about the downstream equipment.

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  • 2 years later...

Anyone with the Pink Faun bridges know if the OCXO clocks are inter-changeable? 

ie, I have both cards. My USB bridge has the added clock, but the i2s doesn't.

 

In the end i'm only going to use one, so it could be nice if "the one" is the i2s i'd be able to use the clock that was on the USB.

 

Thoughts?

 

I kinda looks like they could be, when one buys only the clock it doesn't ask which card it goes too.

It does give options for clock speed... (i also don't understand how the mhz impact on the clocks. For example, If you buy the cards with clocks, they don't ask for clock speeds.)

image.thumb.png.c75e7d6b661d14983662c4dc8909a8e0.png

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update from Pink Faun:

 

Quote

 

The clock from the USB card is different than the clock from the I2S card. You will not damage the system when swapping the OCXO clock, but the music will not play on the same tempo. The USB clock is 20MHz and the I2S clock is 24.576MHz. This has to do with the issue that USB is data transfer and I2S is digital audio stream, very different things.


No problem using a SBooster with the card, please note that with an OCXO clock on the card the power consumption is twice as without OCXO clock.

 

 

 

 

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