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What is I2S
What is I2S
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Old 20th November 2006, 04:40 AM   #1
SamL is offline SamL  New Zealand
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Join Date: Jun 2004
Location: Wgtn
Default What is I2S

Well, it appear I have been living in the cave for the last few years and don't know a thing about I2S.

Reading a few DIY DAC post and I2S input is widely used. Did a quick search and I2S appear to be an output from sound card.

What I like to find out - Is it compatible with the digital output from my CD/DVD player? Can I connect them to the I2S input on the DAC, like the D-I 16 DAC in the "Building the ultimate NOS DAC using TDA1541A" post?

Thanks for your info,
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Old 20th November 2006, 11:46 AM   #2
Alexandre is offline Alexandre
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Join Date: Jan 2004
Location: Brazil
I2S stands for "Inter-IC Sound". It is an interface protocoll for digital audio, used INSIDE cd-players, dacs and the like. It is rarely available externally. There are some products, usually expensive, that have a I2S output or input, in the form of a multi-conductor pin or multiple optical interconnects.

So, it is likely that you will have to modify a CD-transport if you want to connect by I2S to a dac.

Hope this helps.
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Old 20th November 2006, 06:17 PM   #3
ecdesigns is offline ecdesigns  Netherlands
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Join Date: May 2006
Location: Holland
Default Making the connection

Hi SamL,

If you would like to connect your CD player to the octal D-I DAC or the D-I 16 DAC, there is no problem. I am very aware of the fact, people must be able to connect standard equipment.

If you don't intend to mod your CD player, all you need is the SPDIF to differential I2S interface, that is going to be designed soon. Just hook it up to the coax or optical SPDIF output, and connect the differential I2S to the D-I 16 or octal D-I DAC. The SPDIF interface has a on-board shiftregister reclocker that reduces jitter and produces similar sound quality as a direct I2S interface, the digital audio interface will provide Philips output format.

If you like modding, you could use the single ended I2S to differential I2S module, basically a small buffer. Another option is to mount the D-I 16 core / octal D-I DAC core close to the transport, using the plain single ended I2S interface. In both cases the transport must be able to output the Philips format.

I used a differential I2S interface (one twisted wire pair for each of the 3 signals) to minimize interlink jitter and interference. In practice even a 3 meter long differential I2S interlink works fine, producing very low jitter.

I hope this will answer your question.

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Old 21st November 2006, 06:13 AM   #4
InfinityPWS is offline InfinityPWS  Malaysia
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Location: KL
i get to know that the CDROM has spdif output, my concern is the voltage of that output is 5v while the output of a CDP spdif is 1v-2v. Anyone tried the output of a CDROM as the source for I2S ?
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Old 21st November 2006, 06:15 PM   #5
audioengr is online now audioengr  United States
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Join Date: Oct 2003
Location: Central Oregon
I2S, which was developed by Philips is defined as three signals:

SDATA - serial data
SCLK - serial clock - usually 64fs
L/RCLK - delineates left and right data to demux them.

Most I2S interfaces defined by companies, such as Empirical Audio add a fourth signal:

MCLK - Master clock, can be 256fs or 128 fs

These signals are essentially the interface to most modern D/A chips.

The first I believe to try to standardize I2S was Audio Alchemy, who offered both a transport and DAC with the interface. Later, the follow-on company Perpetual Technologies also put the interface on their P-1A and P-3A. They used the mini-DIN, which is a really unreliable connector.

Recently, Empirical Audio and Northstar design are offering I2S interfaces using the RJ-45 connector common for Ethernet networks. Northstar has a Transport and DAC with I2S. Empirical Audio has USB and Wi-Fi computer interfaces with I2S and adds them to inputs on equipment, including several DAC's and the DEQX.

Steve N.
Empirical Audio
The very best in computer audio
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Old 21st November 2006, 08:18 PM   #6
rfbrw is offline rfbrw
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The I2S Specification. Everything else isn't I2S.
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Old 21st November 2006, 08:56 PM   #7
audioengr is online now audioengr  United States
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Location: Central Oregon
Originally posted by rfbrw
The I2S Specification. Everything else isn't I2S.

Unlike S/PDIF I2S leaves a lot for future definition. It does not define signalling levels, termination, SE versus balanced etc....
The very best in computer audio
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Old 5th December 2009, 09:20 AM   #8
assimaki is offline assimaki  Greece
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Join Date: Jan 2008
Location: Athens, Greece
I will like to connect my PC to a perpetual technologies DAC by using the I2S connection.
The output from the terralink converter is I2S in RJ-45 form. The input of PT3A is a 5-pin mini DIN.
Does anybody knows the the conversion from RJ-45 to PT 5-pin mini DIN?
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Old 7th December 2009, 08:16 PM   #9
glt is offline glt  United States
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Default I2S Measurements

I just did some measurements on the I2S lines. Reported in my blog...
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Old 8th December 2009, 07:01 PM   #10
jkeny is offline jkeny  Ireland
Join Date: Feb 2007
Location: Dublin
Thanks glt,
That's useful information & does show that I2S isn't simply a plug & play technology!

I have a question about using a Sabre DAC which will accept MCLK from I2S OR will allow a local asynchronous clock to be used. In this second asynch. case does the quality of the clock in the transmitter have any sonic influence?

I know that people have reported differences, in using the Sabre, between different sources so can anybody explain what is happening?

Edit: I have I2S from a Musiland to Sabre DAC & wondered if I2S from HiFace (with lower jitter clocks) would make any difference in this case as the clock is being re-clocked?

Last edited by jkeny; 8th December 2009 at 07:19 PM.
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