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Post by MartinT on Jan 7, 2019 7:05:22 GMT
There is lots of talk about using I2S as a data transport, so we're starting this thread for general discussions. I 2S, or IIS, stands for Inter-IC Sound and is pronounced 'I-squared S'. It has been used for years as the method of sending PCM digital data from the transport side of a CD player to its DAC. It uses separate data and clocks (as opposed to, say, S/PDIF which embeds the clock in the data) and was originally intended to be an internal connection format of only a few cm in length. What is exciting about I 2S is that we are seeing it being used as an external connection method between transport/streamer and DAC. There are several physical schemes, I 2S over HDMI, or I2S-H (invented by PS Audio), and I 2S over RJ45, or I2S-E, being the two most popular formats. These are not to be confused with real HDMI or ethernet, they just use the connectors to carry I 2S data and clocks. To further complicate things, I2S over HDMI has split into the PS Audio/Audio-GD camp and the Gustard/LKS camp, with the data connection being reversed. See this useful chart for the connections used by many vendors for both HDMI and RJ45. So why use I 2S? The general opinion seems to be that it's the 'purest' form of connection between a modern transport/streamer and DAC, it allows either the sender or the DAC to be the master clock (depending on chipset), and it has the best potential sound quality. Here's some useful information from Audio-GD. So, apart from speedysteve using it for internal connection and gazjam using it for external, who else is using it or considering using it?
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Post by John on Jan 7, 2019 7:29:17 GMT
I am waiting to see how you get on with it. I been doing a bit of research and seems to be a good way forward. I probably aim to go this way in the summer or Autumn
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Post by MartinT on Jan 7, 2019 7:48:39 GMT
I plan to go I2S for streamer -> DAC soon.
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Post by Stratmangler on Jan 7, 2019 8:08:36 GMT
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Post by MartinT on Jan 7, 2019 9:27:44 GMT
The Allo Kali is designed as an I 2S reclocker for the Raspberry Pi.
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Post by MartinT on Jan 7, 2019 9:29:13 GMT
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Post by Deleted on Jan 7, 2019 9:31:38 GMT
This methodology has been around for a quite a while, nothing new other than the which company can claim latest and greatest, as with all formats the conversion from the raw data into he transmission format is the key, have been using this method for over eight years however by the RJ45 system
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Post by Stratmangler on Jan 7, 2019 9:45:04 GMT
The first line of the page I linked to says the most important thing about I2S There's nothing wrong with S/PDIF. I2S is meant to work over 30mm or so, not the 30cm+ of even the shortest HDMI leads. You'd be introducing a nice aerial to pull in lots of lovely RFI.
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Post by Deleted on Jan 7, 2019 9:51:37 GMT
Chris
Pretty much all quality CD players transmit the recovered PCM via I2s in a short co-ax under 6 inches to the receiver chip, which is what it was exactly designed for.
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Post by MartinT on Jan 7, 2019 9:57:48 GMT
There's nothing wrong with S/PDIF. I2S is meant to work over 30mm or so, not the 30cm+ of even the shortest HDMI leads. You'd be introducing a nice aerial to pull in lots of lovely RFI. Erm, no. I2S over HDMI uses differential driver buffers to drive the cable link. There is therefore a degree of common mode rejection.
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Post by jandl100 on Jan 7, 2019 12:44:59 GMT
Audio Alchemy used I2S connection to their Digital Decoding Engine DAC nearly 30 years ago. Can't say it made it the best DAC in the world, even at the time. 😁
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Post by Deleted on Jan 7, 2019 13:35:02 GMT
Audio Alchemy used I2S connection to their Digital Decoding Engine DAC nearly 30 years ago. Can't say it made it the best DAC in the world, even at the time. 😁 I had a DDE v1.0, and I know it is the sort of nonsense that Naim usually come out with, but adding the Power Supply 2 to the DDE made a huge difference and listenable, I would agreed with the Power Supply 1 it was less than pleasant.
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Post by Deleted on Jan 7, 2019 14:33:54 GMT
I had a DDE v1.0, and I know it is the sort of nonsense that Naim usually come out with, but adding the Power Supply 2 to the DDE made a huge difference and listenable, I would agreed with the Power Supply 1 it was less than pleasant. Indeed Paul, however it still was a decent step up over Salisbury's finest digital dross at the time
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Post by Slinger on Jan 7, 2019 15:01:35 GMT
I don't pretend to understand this stuff properly, but surely, at its most basic level, the problem is implementing I 2S in a way that it can feed an external DAC. Why, then, are we not talking about a high-quality onboard DAC that is connectable to a Pi/transport directly to form what is essentially one "product," comprised of 3 modules, that implements I 2S? Just as a " for-instance" a reworked Pi/DigiOne Signature/Kali combo? Surely that makes more sense; using I2S as it's meant to be used rather than adding lots of faffs and workarounds into the signal chain etc. I know it does away with the flexibility of using one's own DAC, but I would have thought it was a logical step, even if only a semi-sideways one. Add a dual LPSU and Robert would appear to be your father's brother...to me at least. Now tell me why I'm being stupid.
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Post by MartinT on Jan 7, 2019 15:08:31 GMT
It's for when you want the flexibility of having a separate streamer/player and DAC, Paul. Otherwise, an all-in-one is likely to use internal I 2S already. What speedysteve has done with his Pi & Najda, for instance. For me, the beauty of an external I 2S connection that can handle a metre rather than a few cms is all about the two-box flexibility, but without compromising by converting to S/PDIF.
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Post by stanleyb on Jan 9, 2019 10:13:12 GMT
Converting to SPDIF is not a compromise. When it comes to digital data it is hard for a 1 or 0 to suddenly disappear. Otherwise we would have terrible problems with our modern banking system.
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Post by MartinT on Jan 9, 2019 10:29:33 GMT
I don't think anyone is saying that, Stan. It's all about ease of clocking and S/PDIF with its embedded clock is more complex and another conversion layer over I2S with its separate clocks.
Saying that, S/PDIF works extremely well when it's reclocked at both ends, in my case by the Allo DigiOne at the Pi end and in the SEG with superclock and firmware at the DAC end. Listening to it again last night, I cannot imagine the lightning-fast timing getting any better than it is already. Therefore, the benefits of I2S have yet to be proven in practice for me.
Forgot to add, S/PDIF is limited to 24/192, which is another limitation yet to be proven in practice.
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Post by Deleted on Jan 9, 2019 10:37:29 GMT
I don't think anyone is saying that, Stan. It's all about ease of clocking and S/PDIF with its embedded clock is more complex and another conversion layer over I 2S with its separate clocks. Saying that, S/PDIF works extremely well when it's reclocked at both ends, in my case by the Allo DigiOne at the Pi end and in the SEG with superclock and firmware at the DAC end. Listening to it again last night, I cannot imagine the lightning-fast timing getting any better than it is already. Therefore, the benefits of I 2S have yet to be proven in practice for me. Forgot to add, S/PDIF is limited to 24/192, which is another limitation yet to be proven in practice. From experience if correctly implemented more depth and textural layering are evident imho SPDIF again if correctly done is more than adequate But is it just one' s and naught's remember you have three data streams embedded inside a PCM transmission, and data timing makes zero difference according to a great many IT guru's that inhabit certain US forums, after all bits are bits
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Post by MartinT on Jan 9, 2019 10:49:58 GMT
I see it all over the internet: the data is either perfect or it stops working, therefore any difference in digital cables is imaginary etc. etc. etc.
Yawn! They are so wrong and they don't even know that they are spreading further misinformation to the uninformed.
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Post by Slinger on Jan 9, 2019 14:45:47 GMT
I promise I'm only playing Devil's Advocate here, and you know I don't have an agenda of any sort, but can the "improvement" gained by using a decent digital cable be measured, or is it all in the ears, so to speak? If no measurement is possible (how square is your square-wave?) then all it comes down to is "I can hear a difference" against "I don't believe there's a difference," and neither party has any sort of proof but will die before believing, let alone admit, that they are in the wrong. What we end up with, of course, is a free-for-all where everyone and his dog has what they consider to be a valid argument, science and pseudo-science abound, everything boils down to "my ears are superior to your ears," and to which there can never be a mutually satisfying resolution. Or, as it's better known, a cable thread.
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