I2S : A Dedicated Thread

drkrack

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Dear FMs,
I am Planning on getting a DAC with I2S inputs. Some have HDMI type of input, Some have RJ45 type ones, Since I'm a total Noob in this topic (and online research is leading nowhere) , want some information from fellow knowledgeable FMs using i2s connections. I couldn't find a dedicated thread on i2s, mods can merge this into any existing dedicated i2s thread if already present.

1. Is this better than USB input, Resolution, Jitter, Background Noise wise?
2. Is i2s connection better than Coax or AES connections?
I know much depends on the implementation in the DAC/Source , what's the general experience?

3. Which i2s connections to opt for Hdmi like or Etherenet type ones? Or something else altogether..
4. I'll be Using a MacBook as Source, any USB to I2S converter that can be recommended?
5. Streamer with I2S output under 1.5L inr will be my next upgrade any recommendations?

Thanks in advance
Hopefully everyone is Safe and Vaccinated
 

firearm12

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I2s is better than coax generally. Keep i2s interconnect short enough less than 30cm if possible. Quality of interconnect also matters. I would prefer ethernet types as you can get short custom cables easily built, short hdmi cables are pain to get.
 

Yelamanchili manohar

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Dear FMs,
I am Planning on getting a DAC with I2S inputs. Some have HDMI type of input, Some have RJ45 type ones, Since I'm a total Noob in this topic (and online research is leading nowhere) , want some information from fellow knowledgeable FMs using i2s connections. I couldn't find a dedicated thread on i2s, mods can merge this into any existing dedicated i2s thread if already present.

1. Is this better than USB input, Resolution, Jitter, Background Noise wise?
2. Is i2s connection better than Coax or AES connections?
I know much depends on the implementation in the DAC/Source , what's the general experience?

3. Which i2s connections to opt for Hdmi like or Etherenet type ones? Or something else altogether..
4. I'll be Using a MacBook as Source, any USB to I2S converter that can be recommended?
5. Streamer with I2S output under 1.5L inr will be my next upgrade any recommendations?

Thanks in advance
Hopefully everyone is Safe and Vaccinated
Only from what I've read I2S is better than aes ebu and then comes usb and coaxial. The I2S wiring implementation has still not been standardised. So everyone's RJ45 wiring is different. During my research both metrum and psaudio offered I2S output streamers, only compatible with the I2S inputs on their own dacs. However, when I last checked, both manufacturers were willing to share their RJ45 implementation. So we can get any local computer guy to wire up the cable accordingly. Infact I needed a long Lan cable is 2017, when I was wiring up my flat. And I got it custom built to my exact required length from a computer shop in chandanagar.


So if you can find a usb to I2S converter that can output via RJ45, then the dac maker can suggest the required wiring protocol I think.
 

firearm12

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All said pls dont have notion that any dac with i2s input will will be better that those without. Select a dac first which can sound appealing to you. I2s is secondary. I2s should not be sole reason to get a dac. Denafrips dacs are considered top of the line dacs these days that are value for money. I2s only helps in transfer between transport and dac where it minimizes jitter. Good quality streamer and good dac will have more impact than just having i2s.

One recommendation from my side for streamer would be sotm sms ultra neo. you can upgrade in future with their power supply and even external clock. Hans bekhuyzen on YouTube says this combo is the highest quality that he has ever listened to. It would output usb to you dac. You can even upgrade to connect to it to a ddc (which reclocks the usb input amd then connects via i2s to dac) and external clocks to ddc. Once you move into this category, clocks become of paramount importance. Mutec ref 10 is one revered external 10 mhz clock that will transform your system for ever. But before all that a good dac would go a long way. Sorry if i confused you.
 
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IndianEars

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I totally agree with firearm12's comment: "All said pls dont have notion that any dac with i2s input will will be better that those without. Select a dac first which can sound appealing to you. I2s is secondary. I2s should not be sole reason to get a dac."

It would be like putting the Cart before the Horse .....

To Moderators, I intend a total of 3 posts ....this is the second. < Moderator edited to 2 to improve readability>

Since each post will address a different topic and posts 2 & 3 are long, I would prefer that they be preserved as 3 separate posts rather than being telescoped into a single, tedious post.


I2S, AES/EBU, SPDIF, TOSLINK & USB INTERFACES FOR DIGITAL AUDIO
Let me attempt to clarify on the different interfaces, with a bird's eye view, and without getting very technical.

A DAC (Digital to Analog Converter) receives Digital Data for 2 separate (stereo) Audio Channels.

As an example, a CD mechanism will read (off the CD) 16 Bits of Info, 44,100 Times per second, for each channel ie 16 x 44,100 x 2 = 1.4112 MegaBits (Million Bits) per second. This data is fed to the DAC which needs to
1. Receive the Data
2. Told if its receiving the Left or Right Channel Data
3. Receive a Clock signal which acts like an orchestra Conductor, synchronising all the Data.


I2S INTERFACE
The I2S interface provides separate wires for each of these and a Ground wire. Hence 4 separate wires are used in the i2S interface to convey data to a DAC.

The I2S interface is the UNIVERSAL Internal interface for all DACs.
Since it is primarily an internal interface, its signals were never designed to be carried over long lengths of wire of from 1 box (transport) to another (DAC).

Long wire lengths with their inductance & capacitances will corrupt the digital signals.

Also running 4 wires externally is in-elegant and difficult if circuit impedances are to be maintained.

AES/EBU
The Audio Engineering Society (AES) jointly with the European Broadcast Union (EBU) standardised a THREE WIRE Interface, for external interconnection of digital signals.
All the data signals are jumbled up (multiplexed) onto just TWO wires. The third wire is ground.

SPDIF

Sony & Philips (the Joint inventors of the CD) went a step further and developed the Sony Philips Digital InterFace (SPDIF) that jumbles up (multiplexes) all the digital signals onto a SINGLE Wire carrying the signal, with the second wire (the Shield of a Coaxial Cable) being the ground. SPDIF was designed for 16/44 data transmission used in CDs

TOSLINK
TOshiba & Sony invented a low cost, suitable for mass manufacture, Optical interface that can be thought of as the optical equivalent of the SPDIF Interface.
Instead of the Electrical Digital 1s & 0s, and LED Blinks On and Off. These blinks of light are transmitted via a low cost transparent Plastic cable over distances of 5 m to 10 meters.

USB
With the widespread use of computers in digital audio, it became necessary to adopt a common computer interface for use with digital Audio & DACs.
The Low cost and widely used, 4 wire USB-1 / USB-2 interface was adopted.
The Digital Signal is adapted to be carried over a USB interface which uses 2 wires for Data and 2 wires for the Positive & negative DC power.

SUMMARY
As one can instinctively conclude, carrying all signals via their separate wires (I2S) is the best. But I2S was never designed for any reasonable length of wire. Taking special care, it can be reliably transmitted over approx.. 30 cms or 1 foot, but even that is not Easy.

AES/EBU Digital jumbles the signal, over 2 signal wires. In this respect, it is certainly worse than I2S.

SPDIF takes the Matter to the Extreme, jumbling all signals over a single wire.

TOSLINK is the optical equivalent of the SPDIF interface but provides electrical isolation between the sending and receiving boxes.

USB processes the digital signal, for carriage on 2 separate Data wires..... However, so much work and technology (e.g., Asynchronous Transmission) has gone into the USB interface that today it is the most widely used digital audio transmission interface. Also, USB-2 is capable of Very high speed data transmission, far higher than any Digital Audio signal today. Hence the USB interface has emerged as a defacto standard.
 
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IndianEars

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CONNECTORS USED FOR EXTERNAL I2S

There is a lot of confusion regarding connectors suitable for an external I2S cable.

The I2S is a high-speed interface and needs High Speed connectors that can provide atleast 4 signal wires.

The HDMI (High-Definition Multimedia Interface ) is an Excellent choice with 19 wires, but there are Huge Commercial implications.

HDMI can be used ONLY under license.

A manufacturer using HDMI must pay an annual fee of US $ 10,000.
This is a flat fee, irrespective of the number of units or connectors!

While the amount is not significant for say, a TV manufacturer producing 1 million TV a year (amounts to 1 cent per TV) the economics do not work out for a High End DAC Manufacturer who may produce 100 to 500 DACs per year, each probably with an Ex-Factory price of $1000 to $3,000.

Hence though some big names in High End audio do use HDMI, it is unaffordable for boutique manufacturers.

(Incidentally, there is also an additional royalty of $1 per HDMI connector used, but than can be reduced to about 10 cents, if the device manufacturer prominently states on the product / Packing "HDMI".... However, that is another story!)

RJ45 ETHERNET CONNECTOR
Boutique Audio DAC manufacturers have looked for a High Speed non-royalty connector, and found it in the humble RJ45 Ethernet connector used widely in LAN networks. The connector supports Gigabit speeds, offers 8 wire connectivity and costs pennies.

The use of RJ45 in audio has not been standardised by any body or association. Hence there is no standard Pin Configuration for the pins allocated to the 4 I2S wires, out of the 8 pins on the RJ45 connector.

There is also no standardised characteristic impedance to ensure ideal signal transmission.

As a result, the I2S out from one manufacturer may not / will not t6alk to the I2S in of another manufacturer.

Since there is no secrecy involved, manufacturers will almost always share their Pin out sequence used by them on the RJ45. It is then left to the user to switch wires around in the Ethernet interconnection cable, to make the sender & receiver talk to each other.

A further twist is the impedance.... even after adapting the wire in & outs, the transmitter or receiver may need external resistors to be inserted. I recall a friend years ago tried to use the I2S interface on his Ayon DAC. Ayon shared their pin out configuration and asked for external 45 ohm resistors in series with each of the 4 signal wires, but somehow, the Ayon I2S interface never worked with that of another manufacturer's CD Transport.

This should be a sobering warning to anyone planning to use the I2S interface between products by 2 different manufacturers.
 

Nikhil

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Moderator Note:
Please assume that the OP already knows and understands digital.
So while other aspects are important such as DAC and Clocking etc, please limit this thread to I2S




.
 

Nikhil

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Found out about the Pink Faun I2S Bridge while browsing another thread.


The Pink Faun I2S Bridge is an HDMI implementation
They offer a drop down menu of compatible I2S DACs for implementing the appropriate pin outs.

i2s-bridge.jpg



.
 

IndianEars

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Found out about the Pink Faun I2S Bridge while browsing another thread.


The Pink Faun I2S Bridge is an HDMI implementation
They offer a drop down menu of compatible I2S DACs for implementing the appropriate pin outs.

i2s-bridge.jpg



.
Super Info.

I wonder how it gets the 4 wire I2S bus. If its from the PC's internal bus, that is great.

If however it is synthesised from the internal SPDIF or whatever, it would defeat the purpose.... like recreating a wav file from a 128Kbps mp3....:(

Thanks.
 

johnmicheal

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As pink faun audio owner, he likes AES better than USB and I2S.I have I2s Over USB card which gives I2S output and used it with TPA buffalo's ESS9038 dac. For I2S ,cable length should not be more than 100mm and Hirose cables should be used as per Wave IO owner.
 

rsjaurr

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Super Info.

I wonder how it gets the 4 wire I2S bus. If its from the PC's internal bus, that is great.

If however it is synthesised from the internal SPDIF or whatever, it would defeat the purpose.... like recreating a wav file from a 128Kbps mp3....:(

Thanks.

This is a PCIe card so it is from the internal bus. This also means they have all the pin-out information of the compatible DACs shown in the drop down menu. They already have similar PCIe to USB cards available and as the USB interface is also 4-wires, for them it is a simple modification to turn USB to i2s. This i2s interface could be either HDMI or RJ45 and as per the pin-out arrangement information available to them.

So most likely they will be making these cards on orders for a particular DAC and won't be readily available.
 

IndianEars

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Just a minor point when you say "as the USB interface is also 4-wires, for them it is a simple modification to turn USB to i2s."

The USB has Two wires for Data. The Other 2 wires are for +ve & -ve supply.

The I2S interface has 3 Wires carrying Digital Data and 1 wire as common
Ground.
 

arj

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Just a minor point when you say "as the USB interface is also 4-wires, for them it is a simple modification to turn USB to i2s."

The USB has Two wires for Data. The Other 2 wires are for +ve & -ve supply.

The I2S interface has 3 Wires carrying Digital Data and 1 wire as common
Ground.
Could not the power supply wires be repurposed for data ? unless of course the specs of the wire are not relevant for I2S.
 

IndianEars

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The USB-1 / 2 connector and its 4 wires are standardised. The sequence is written in stone. This is to ensure that every USB-1 / 2 is intercompatible, and that plugging a USB into any USB receptacle will not cause device damage.

Imagine if some device fed +5V into the data, or Grounded the data bus... or Grounded the 5V supply ...... :oops:
 

arj

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Not disputing that in fact some years back I made a double header USB cable with power in one and data on the other going to a single USB male plugged into the device to see if separation of power improved sound..and it did

the point i was trying to make is if both ends of the USB cable are re-purposed for I2S..instead of using HDMI/Ethernet. Am sure there is some issue else someone would have thought of it before! This is of course assuming the source should not be plugged into any USB source..it might all go kaboom with a small puff :) and which is what you are saying I suppose
 

rsjaurr

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Just a minor point when you say "as the USB interface is also 4-wires, for them it is a simple modification to turn USB to i2s."
For someone who is able to make PCIe audio cards it should be a simple task to convert PCIe audio data to i2s instead of USB which they were doing earlier.That's what I meant actually.

Full marks to them for accessing the pinout information of different DACs and using that information to bring out i2s bridge.
I have been using a PCIe to USB card myself and have seen improvements and may consider bridge in future.
 

IndianEars

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Are you using an SoTM PCIe to USB Card ? I had tied one Years ago (it was a PCI Card) and was VERY Happy with the results.
 

IndianEars

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Not disputing that in fact some years back I made a double header USB cable with power in one and data on the other going to a single USB male plugged into the device to see if separation of power improved sound..and it did

the point i was trying to make is if both ends of the USB cable are re-purposed for I2S..instead of using HDMI/Ethernet. Am sure there is some issue else someone would have thought of it before! This is of course assuming the source should not be plugged into any USB source..it might all go kaboom with a small puff :) and which is what you are saying I suppose
Good Point, Arj

I remember several decades ago, when I had begun Audio DIY, an article repeatedly warned against terminating Speaker Cables with a 2 Pin Plug..... :p
 
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