Study: Is I²S interface better for DACs than S/PDIF or USB?

[Roland68]

I prefer I2S over USB.

That's exactly how I do it.
I use the USB I2S digital interface PCM1536 from Xing Audio (was introduced by Wolf in the forum) on which an i2s -> HDMI (LVDS) board is plugged. A 0cm HDMI cable (Male / Male HDMI adapter) goes directly from the board into my DAC.

 

[Veri]

That's exactly how I do it.
I use the USB I2S digital interface PCM1536 from Xing Audio (was introduced by Wolf in the forum) on which an i2s -> HDMI (LVDS) board is plugged. A 0cm HDMI cable (Male / Male HDMI adapter) goes directly from the board into my DAC.

But you use USB to get the I2S to plug into the HDMI connector. So instead of DAC-USB input you use USB > I2S > DAC. Right?
I use the same Xing for s/pdif output. It's a good device. I still don't see the point of using it for I2S, just another (unnecessary) board.

 

[mansr]

One of the earliest examples of external I2S I know of (and had used) was in Audio Alchemy gear in mid 90's. It was on a mini-DIN type connector (diagram from Sonore's Jesus Rodriguez spreadsheet of known I2S connectors). This format made into a few products by other companies, as well, and even inspired some "improved audiophile" versions of I2S silver cables, IIRC:

View attachment 155881

It should be noted that "master clock" is not part of the I2S spec.

 

[Roland68]

But you use USB to get the I2S to plug into the HDMI connector. So instead of DAC-USB input you use USB > I2S > DAC. Right?
I use the same Xing for s/pdif output. It's a good device. I still don't see the point of using it for I2S, just another (unnecessary) board.

My Xing Board only has USB input and i2s output. There is no conversion and the i2s data stream is sent directly to the DAC chip.
Do you have the AF200 from Xing Audio?

 

[mansr]

That's exactly how I do it.
I use the USB I2S digital interface PCM1536 from Xing Audio (was introduced by Wolf in the forum) on which an i2s -> HDMI (LVDS) board is plugged. A 0cm HDMI cable (Male / Male HDMI adapter) goes directly from the board into my DAC.

Does your DAC not have a USB input?

 

[sarumbear]

Much too late; o)
There are thousands of satisfied users of i2s over LVDS worldwide. Alone the whole users of the digital USB converters from Gustard, Xingser, Audio GD etc., plus many streamers and DAP with this interface (and there are more and more).

If that was the argument; 90% of all audio gear would be perfectly acceptable as they are used worldwide. However, we know here at ASR that they are not acceptable. Why use the satisfaction as a criteria when there are millions of satisfied users of those equipment we would lough at?

 

[Roland68]

Does your DAC not have a USB input?

I have several DACs and from time to time also guest devices. Most of course have a USB input.

 

[sarumbear]

I have several DACs and from time to time also guest devices. Most of course have a USB input.

Why do you then prefer to go all that trouble using rare equipment to customise your computer instead of using USB?

 

[mansr]

If that was the argument; 90% of all audio gear would be perfectly acceptable as they are used worldwide. However, we know here at ASR that they are not acceptable. Why use the satisfaction as a criteria when there are millions of satisfied users of those equipment we would lough at?

The real test should be, is Mick Jagger satisfied?

 

[Roland68]

If that was the argument; 90% of all audio gear would be perfectly acceptable as they are used worldwide. However, we know here at ASR that they are not acceptable. Why use the satisfaction as a criteria when there are millions of satisfied users of those equipment we would lough at?

Please don't twist the words in my mouth, that's extremely rude and unobjective.
My statement was based solely on the satisfaction with the interface and you can read that too. I didn't make any statements about the devices.

My statements about the interface also relate to my experience with over 40 devices and modules. And so far they have all worked well with each other.
What is your own experience with these interfaces so far?

Why do you then prefer to go all that trouble using rare equipment to customise your computer instead of using USB?

What effort? I just plug the HDMI connector into each DAC.
I have an absolutely (for me) standardized connection from the USB port of my computer to the i2s / HDMI port, i.e. almost to the i2s input of the DAC chip. So every DAC with this connection has the same requirements for me. This is important to me and therefore not worth discussing.

 

[sarumbear]

Please don't twist the words in my mouth, that's extremely rude and unobjective.
My statement was based solely on the satisfaction with the interface and you can read that too. I didn't make any statements about the devices.

My statements about the interface also relate to my experience with over 40 devices and modules. And so far they have all worked well with each other.
What is your own experience with these interfaces so far?


What effort? I just plug the HDMI connector into each DAC.
I have an absolutely (for me) standardized connection from the USB port of my computer to the i2s / HDMI port, i.e. almost to the i2s input of the DAC chip. So every DAC with this connection has the same requirements for me. This is important to me and therefore not worth discussing.

I not twisting your words. If it reads that way I apologise. I am simply asking questions to understand why would anyone prefer to use I2S?

PCs are not shipped with a card that has an HDMI connector that sends data via LVDS/I2S. You have to buy a specific card, a relatively expensive one, in order to have that connection. (There is no I2S bridge PCI card displayed on Amazon UK in the first three pages. It is that rare!) Besides, a standard audiophile would not necessarily have the knowledge to find and install an internal card. So it's not exactly like I'm plugging a cable is it?

So I repeat my question: what is the benefit of I2S compared to a USB connection, which standard on every computer?

 

[sarumbear]

It should be noted that "master clock" is not part of the I2S spec.

From what I can read on the the original Philips datasheet, clock is very much part of I2S. I2S as defined by Philips has three elements:

• serial data (SD) bus
• continuous serial clock (SCK) signal
• word select (WS) signal

We are told I2S had data and clock signals only? How come SD is ignored?

 

[mansr]

From what I can read on the Philips notes, clock is part of I2S but not part of the protocol.

I2S specifies three signals: serial clock (aka bit clock), word select (aka word clock or LR clock), and data. Oversampling DAC chips typically require an additional high-rate clock, usually called master or system clock, which is not part of the I2S interface.

 

[Lupin]

Maybe I'm completely missing the point and totally stupid but...

The XMOS USB interface in a USB desktop DAC converts USB > I2S that get send to the DAC chip.
So what is the benefit/added value of adding an extra box that you connect USB from the computer and outputs I2S through HDMI cable to the DAC?
I2S supports PCM 1536 and DSD 1024, is that really such a big deal compared to PCM 786 and DSD 512 that most XMOS based DACs support?

 

[pkane]

So I repeat my question: what is the benefit of I2S compared to a USB connection, which standard on every computer?

For at least one of the DACs I've tested, I2S was needed with an external DDC to support higher DSD rates that were not supported directly over USB.

What effort? I just plug the HDMI connector into each DAC.
I have an absolutely (for me) standardized connection from the USB port of my computer to the i2s / HDMI port, i.e. almost to the i2s input of the DAC chip. So every DAC with this connection has the same requirements for me. This is important to me and therefore not worth discussing.

Not my experience. Look at the spreadsheet to see all the different configurations depending on manufacturer.

 

[sarumbear]

For at least one of the DACs I've tested, I2S was needed with an external DDC to support higher DSD rates that were not supported directly over USB.

Not my experience. Look at the spreadsheet to see all the different configurations depending on manufacturer.

Was that test before or after USB3 became available (2009)?

That spreadsheet is an excellent source but my stipulation is that the average person will not open their computers and plug in a card that the corner IT shop or the help desk at a nationwide PC seller haven't heard about. I believe that you belong to a very small minority.

 

[pkane]

Was that test before or after USB3 became available (2009)?

That spreadsheet is an excellent source but my stipulation that the average person will not open their computers and plug in a card that the corner IT shop or the help desk at a nationwide PC seller haven't heard about. I believe that you are a very small minority within a small minority that owns a separate DAC.

How many DACs actually use USB3?

 

[mansr]

From what I can read on the the original Philips datasheet, clock is very much part of I2S. I2S as defined by Philips has three elements:

• serial data (SD) bus
• continuous serial clock (SCK) signal
• word select (WS) signal

We are told I2S had data and clock signals only? How come SD is ignored?

I don't understand the question. The clock (SCK) defines when the data (SD) is valid. The word select (WS) is needed for the receiver to know where the sample boundaries are. If either one of these three signals is removed, what remains is useless. I don't know that anyone is ignoring anything.

 

[mansr]

How many DACs actually use USB3?

None that I've ever heard of.

 

[Roland68]

I not twisting your words. If it reads that way I apologise. I am simply asking questions to understand why would anyone prefer to use I2S?

PCs are not shipped with a card that has an HDMI connector that sends data via LVDS/I2S. You have to buy a specific card, a relatively expensive one, in order to have that connection. (There is no I2S bridge PCI card displayed on Amazon UK in the first three pages. It is that rare!) Besides, a standard audiophile would not necessarily have the knowledge to find and install an internal card. So it's not exactly like I'm plugging a cable is it?

So I repeat my question: what is the benefit of I2S compared to a USB connection, which standard on every computer?

You may have missed it, I'm using USB. It's also far from expensive. The Xing Audio USB to i2s Board costs around € 60, the i2s to HDMI (LVDS) is around € 15-20. With a CD player you only need the i2s to HDMI (LVDS) board to pick up the i2s signal.
As I said, it's the best solution for me so far. That doesn't have to apply to anyone else.

But to answer your real question.
If I have a source device (DAP, CD player, streamer) that outputs an i2s (LVDS) signal without a detour (even without USB) that the DAC chip can process directly as a normal i2s signal, why should I use that in change anything else? It will definitely not get any better. And it has to be changed back again. In addition, the data is transmitted differentially, how could that be better?

There is actually an expensive i2s card for the PC, but since I don't have a PC, I cannot use this card at the moment. If the connection is USB based, it would make no sense.