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Old 22nd November 2014, 10:38 PM   #1
Magz is offline Magz  United States
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Default What are You using for an I2S Connection?

Hello,

I'm currently building a DAC and am at the point where I need to decide on connectors/jacks. The DAC supports both S/PDIF and I2S, and I've already decided on BNC coax for the S/PDIF, but it seems there's not really a standard solution for I2S.

I'd like to put the I2S connector on the back on the unit and use an external conversion box for whatever the external interconnect standard evolves to be (USB or something else...to I2S). I'm leaning toward a Cat6/RJ-45 for the DAC box, but I'm curious as to what others are using and why.

Also, Is there a standard for which pins of the RJ-45 connect to which parts of the I2S signal?

Any help is greatly appreciated as I'm experienced in building tube circuits but am a newbie to digital DIY.

Last edited by Magz; 22nd November 2014 at 10:42 PM.
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Old 23rd November 2014, 04:54 AM   #2
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I came up with one not too long back.

Haven't actually built it yet but I do have the edge connectors and the coax.

The specs are:
Source (I2S side of an SP-DIF Receiver or direct from your CD Player).
RP-SMA Female PCB Edge connectors.

Receiver: (DAC IC)
RP-SMA MALE PCB Edge connectors.

And for the interconnect cable:
RG-316
http://img.banggood.com/images/uploa...Connector1.jpg

You can get RP-SMA extension cables with Male on one end and Female on the other in RG-316 rather cheaply from Hong Kong at lenghts of about 15cm for really cheap.

The nice thing about RG-316 though is that its fairly easy to solder it directly to a board without using a connector, and then make two holes int he PCB and cable tie it down. So if you wanted to you can adapter it to systems which don't cater for the edge connectors.

I'm using one coax cable for each I2S line.
So For I2S you would need 3x coax cables.

http://www.l-com.com/what-does-rg316-u-mean

The reason why I settled on RP-SMA is because its a lot easier to find the connector because of its wide use in WiFi devices than compared to say SMA.

I use BNC for Analog too aswell as for SP-DIF. Though I'm going to be moving away from SPDIF as a transport soon probably and going to pure I2S.
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Last edited by freax; 23rd November 2014 at 05:09 AM.
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Old 23rd November 2014, 08:18 AM   #3
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Quote:
Originally Posted by Magz View Post
Hello,

I'm currently building a DAC and am at the point where I need to decide on connectors/jacks. The DAC supports both S/PDIF and I2S, and I've already decided on BNC coax for the S/PDIF, but it seems there's not really a standard solution for I2S.

I'd like to put the I2S connector on the back on the unit and use an external conversion box for whatever the external interconnect standard evolves to be (USB or something else...to I2S). I'm leaning toward a Cat6/RJ-45 for the DAC box, but I'm curious as to what others are using and why.

Also, Is there a standard for which pins of the RJ-45 connect to which parts of the I2S signal?

Any help is greatly appreciated as I'm experienced in building tube circuits but am a newbie to digital DIY.
I may be misreading you but it appears that you're wanting to use an RJ45 connector (or similar) on the back of your DAC as an I2S input to the DAC?

I2S signal paths should be kept as short as possible, ideally around 10cms maximum. Longer runs will result in signal degradation or might not work at all. The I2S standard was originally written for interfacing at the chip level on PCBs.

If you want to send I2S to your DAC from a remote source component I suggest using a pair (send/receive) of LVDS transceivers such as the Twisted Pear Teleporter modules;

Teleporter Digital Transfer Module

Ray
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Old 23rd November 2014, 12:27 PM   #4
Magz is offline Magz  United States
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Quote:
Originally Posted by nautibuoy View Post
I may be misreading you but it appears that you're wanting to use an RJ45 connector (or similar) on the back of your DAC as an I2S input to the DAC?

I2S signal paths should be kept as short as possible, ideally around 10cms maximum. Longer runs will result in signal degradation or might not work at all. The I2S standard was originally written for interfacing at the chip level on PCBs.

If you want to send I2S to your DAC from a remote source component I suggest using a pair (send/receive) of LVDS transceivers such as the Twisted Pear Teleporter modules;

Teleporter Digital Transfer Module

Ray

Yes, I've been looking at the Teleporter as an option (although it reads out of stock at TP). My other thought was to have the RJ45 connector on the back of the DAC box with a very short lead to the DAC board, and then I'd be able to add an external interface box for whatever the communication standard turned out to be in the future. I guess the Teleporter is a much slicker option at this point...when it comes in stock.

Thanks!
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Old 23rd November 2014, 01:23 PM   #5
Magz is offline Magz  United States
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Quote:
Originally Posted by freax View Post
I came up with one not too long back.

Haven't actually built it yet but I do have the edge connectors and the coax.

The specs are:
Source (I2S side of an SP-DIF Receiver or direct from your CD Player).
RP-SMA Female PCB Edge connectors.

Receiver: (DAC IC)
RP-SMA MALE PCB Edge connectors.

And for the interconnect cable:
RG-316
http://img.banggood.com/images/uploa...Connector1.jpg

You can get RP-SMA extension cables with Male on one end and Female on the other in RG-316 rather cheaply from Hong Kong at lenghts of about 15cm for really cheap.

The nice thing about RG-316 though is that its fairly easy to solder it directly to a board without using a connector, and then make two holes int he PCB and cable tie it down. So if you wanted to you can adapter it to systems which don't cater for the edge connectors.

I'm using one coax cable for each I2S line.
So For I2S you would need 3x coax cables.

What does RG316/U mean?

The reason why I settled on RP-SMA is because its a lot easier to find the connector because of its wide use in WiFi devices than compared to say SMA.

I use BNC for Analog too aswell as for SP-DIF. Though I'm going to be moving away from SPDIF as a transport soon probably and going to pure I2S.
Thanks for the reply. So many options can be confusing, especially trying to guess where the technology is going in the future!
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Old 23rd November 2014, 03:12 PM   #6
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K and K Audio do an alternative to the Teleporter, look towards the bottom of this page;

K & K Audio - Lundahl Transformers, audio DIY kits and more

It uses HDMI connections rather than Ethernet but its the functionality that is important, not the physical implementation.

Of course, there may be others.

Ray
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Old 24th November 2014, 10:47 AM   #7
marce is offline marce  United Kingdom
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Actually the physical implementation is critical to I2S going off board as you said Nautibuoy stated above, this means keeping the impedance mismatches to a minimum, and in this case making sure the return path is unbroken, some high speed connectors from the like of Samtec would be best, they are designed for these type of signals, or the co-ax solution Freax mentioned.

Last edited by marce; 24th November 2014 at 10:55 AM.
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Old 25th November 2014, 12:43 PM   #8
erin is offline erin  Australia
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Quote:
Originally Posted by Magz View Post
Hello,

I'm currently building a DAC and am at the point where I need to decide on connectors/jacks. The DAC supports both S/PDIF and I2S
Does this mean you are interrupting the on board i2s lines with some relays or digital switch in order to switch between a digital receiver and the external i2s?
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Old 26th November 2014, 08:22 PM   #9
Magz is offline Magz  United States
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Quote:
Originally Posted by erin View Post
Does this mean you are interrupting the on board i2s lines with some relays or digital switch in order to switch between a digital receiver and the external i2s?
No, the DAC itself can switch between I2S and S/PDIF inputs with a simple contact closure switch. It's a Buffalo IIISE.
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Old 26th November 2014, 11:44 PM   #10
erin is offline erin  Australia
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OK, so you are using the ES9018 onboard spdif reciever.
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