What is Spdif ?

[Audio Al]

SPDIF, also written as S/PDIF, stands for Sony/Phillips Digital Interface, and is an interface to transmit digital audio. ... Currently, there are two consumer-level interfaces to transmit audio in digital format: SPDIF and HDMI (High-Definition Multimedia Interface).

Now you and I both know :)

[CageyH]

What about AES/EBU then?

Otherwise known as AES3 I believe.

[Firebottle]

IIS HDMI is not a 'standard' for audio transfer as such, it just uses HDMI cables. I believe Gazjam uses this protocol with his kit.

AES uses XLR connectors and has an impedance of 110 ohms, whereas SPDIF is unbalanced an has an impedance of 75 ohms.

SPDIF can be connected to AES over short runs usually without problem, it is how I have my DAB tuner connected to my dac.

[Audio Al]

AES3 (also known as AES/EBU) is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of PCM audio over several transmission media including balanced lines, unbalanced lines, and optical fiber.[1]

AES3 was jointly developed by the Audio Engineering Society (AES) and the European Broadcasting Union (EBU). The standard was first published in 1985 and was revised in 1992 and 2003. AES3 has been incorporated into the International Electrotechnical Commission's standard IEC 60958, and is available in a consumer-grade variant known as S/PDIF.

[CageyH]

Yes, but you are forgetting about USB, which although not strictly a dedicated audio interface, it is widely used.

[Bencat]

Is TOSLINK not also a digital signal standard ?

[Audio Al]

Is TOSLINK not also a digital signal standard ?

Isnt Toslink and optical the same thing ?:scratch:

[Bencat]

My understanding is that Optical is the type of cable used but the protocol is named TOSLINK . In the same way as coaxial cable is the type of cable but the protocal is named SPDIF .

Then again this may well be wrong as these days i often get confused.

[Pharos]

We are in an age of multiple standards, misinformation, and the passing on of poor information by so many, and as someone who tries to adhere to the principle of intellectual rigour in all I do, I find this intensely annoying

[Qwin]

In reality all equipment uses i2s and it is a standard.
It is the internal top level Audio bus on PC's, DAC's, CD players etc, designed for short distance (Internal) connections.

All the other digital audio transfer systems SPDIF optical/coax or AES/EBU or USB are methods for sending over longer distances, what ever method is employed, the i2s has to be repackaged to send, then converted back to i2s at the other end.

Companies are now using i2s to connect box to box over longer distances, they do this by using a simple line driver circuit to extend the range.
This is outside the original i2s spec, so as such there is no standard for this type of application and companies are tackling this by whatever method suits them.
Consequently there are RJ45, BNC and HDMI solutions, with different pin out options adding further to the confusion and the chance of incompatibility.

Although it seems logical to use one system throughout, avoiding multiple conversions and many people rave about i2s results, its not as straight forward as it would seem and relies on how well the method is implemented (Like everything). As an example, I have a NuPrime CDT-8 Pro (CD Transport) with i2s over HDMI output. I also have a PS Audio Stellar DAC/Pre Amp with i2s over HDMI input. The i2s link produces a very detailed sound, but its a bit dead and uninvolving to me and I prefer the coax SPDIF Ouput/Input between these items. Go figure!

I'm in the process of putting together a Pi 4 music server and I've obtained Hat boards to try two different digital output methods:

1). An Allo Kali i2s re-clocker which I've connected to an Audio-GD i2s (HDMI) line driver board, for i2s output.
2). An Audiophonics reclocking AES/EBU output board.

Just ordered a Topping D90 DAC which supports both these digital transfer methods.
It will be interesting to find out which method produces the best results, it will only reflect the results of these boards working with a particular DAC, but interesting anyway.
Then I'll build my Music server using this method.
I'll report my findings in a new thread.

It's worth re-stating that i2s over HDMI simply uses the sockets/cables as a convenient off the shelf connection and is not compatible with the HDMI standard or equipment.

[Barry]

Good post Ken, thanks for the clarification.

[Audio Al]

In reality all equipment uses i2s and it is a standard.
It is the internal top level Audio bus on PC's, DAC's, CD players etc, designed for short distance (Internal) connections.

All the other digital audio transfer systems SPDIF optical/coax or AES/EBU or USB are methods for sending over longer distances, what ever method is employed, the i2s has to be repackaged to send, then converted back to i2s at the other end.

Companies are now using i2s to connect box to box over longer distances, they do this by using a simple line driver circuit to extend the range.
This is outside the original i2s spec, so as such there is no standard for this type of application and companies are tackling this by whatever method suits them.
Consequently there are RJ45, BNC and HDMI solutions, with different pin out options adding further to the confusion and the chance of incompatibility.

Although it seems logical to use one system throughout, avoiding multiple conversions and many people rave about i2s results, its not as straight forward as it would seem and relies on how well the method is implemented (Like everything). As an example, I have a NuPrime CDT-8 Pro (CD Transport) with i2s over HDMI output. I also have a PS Audio Stellar DAC/Pre Amp with i2s over HDMI input. The i2s link produces a very detailed sound, but its a bit dead and uninvolving to me and I prefer the coax SPDIF Ouput/Input between these items. Go figure!

I'm in the process of putting together a Pi 4 music server and I've obtained Hat boards to try two different digital output methods:

1). An Allo Kali i2s re-clocker which I've connected to an Audio-GD i2s (HDMI) line driver board, for i2s output.
2). An Audiophonics reclocking AES/EBU output board.

Just ordered a Topping D90 DAC which supports both these digital transfer methods.
It will be interesting to find out which method produces the best results, it will only reflect the results of these boards working with a particular DAC, but interesting anyway.
Then I'll build my Music server using this method.
I'll report my findings in a new thread.

It's worth re-stating that i2s over HDMI simply uses the sockets/cables as a convenient off the shelf connection and is not compatible with the HDMI standard or equipment.

I admire your knowledge , but must say that went over my head for a numpty like me :doh:

[Qwin]

Don't worry about it Al
Like most of us, your interest is the music and not becoming an expert in electronics, which I am definitely not.

In very simplistic terms, so no one jump on the technical details:

Each piece of equipment is like an onion, with the processor at the centre and the various tasks and hardware are rings or layers around it.
i2s is the, audio only, bus, that is located in the ring closest to the processor and the processor only speaks i2s, so everything else has to go through the i2s bus to talk to the processor regarding Audio. A serial bus is just a method of moving data around the products circuit boards and i2s is a short range serial bus.
On rings further out from the processor you have things like the Universal Serial Bus (USB) and SPIDIF, these are used to send digital audio further afield, to other equipment.

One of the basic differences between the protocols, is that i2s is a multi stream system, it has several channels or wires that transmit several things simultaneously. These are things like the data itself, master and word clock information, each on its own channel.

When the audio is exported using Coax SPIDIF for instance, this is a single stream/channel/wire system, so the multi stream i2s has to be broken down into small packets which are sent in alternate bursts down the single wire. A chunk of data followed by a chunk of clock info etc etc. This has to be re assembled at the other end (piece of equipment) back into a multi stream signal (i2s) that the receiving processor can understand.

To get back to your original question, what is SPIDIF?
When digital audio in the form of CD first appeared, studios that made these digital recordings, used balanced signals almost exclusively and took up using the balanced AES/EBU standard as they still do. Balanced is an inverted and non-inverted signal and is a bit complicated (read expensive), so Sony and Phillips, who invented CD, modified the AES way of doing things and came up with their own interface that was cheaper to implement for domestic equipment. They created the term SPIDIF for this interface, based on their combined names. This SPIDIF information can be sent using an electrical (coax) or Optical (Toslink) cable. The sending methods might be different, but the Protocol is the same so it is easily converted either way. Because it deviated away from AES it is not quite as compatible with it, but they are all based on the same basic method of single stream transmission. USB is different in this respect.

What companies are doing now, is boosting the multi stream i2s signal and sending it to another device unaltered. So you have direct communication, between systems closer to the heart of the processor, without all the packing and unpacking required to send down one wire.

This seems the obvious way of doing things, but as I said previously, its all in the detail, implementation seems to be different case to case, so not a Black and White choice. Eventually a standard might be drawn up and this might help with basic compatibility and consistency of quality across Brands.

I used to think Turntable set up was complex and digital brought a simplicity to enjoying your music.
Unfortunately that is anything but the truth and it's a complex convoluted subject, full of trip hazards for the unwary music lover, wondering which bit of kit to spend his hard earned cash on. Yes, it is all compatible at a basic level and will produce some sort of sound, but is it the optimum method you have chosen. These things are there to haunt us. :)

[Audio Al]

Ken , your a star , I think :hmm: it's beginning to make sence

I get the onion , I get the onion rings ( normally with a curry :eyebrows: ) and some of what you said sounds like flyby wire systems

Thanks for taking the time and sharing your knowledge :D