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I started an article on making custom I2S cables, but I never published how to make CAT5/CAT6 cable on your own using top quality materials. Today I will be showing how I made Belden 1303E Catsnake™ CAT6A (S/FTP 4PR 24AWG) into the I2S interconnect between my FUN01 V1.1 (Singxer SU-1 clone) and my ES9038Pro primary DAC. At the custom ES9038Pro DAC I have a Neutrik NE8FDV-Y110-B (CAT6A in with a punch down block/keystone jack on the rear). The final connections made on the DAC’s PCB (between keystone jack and I2S in) is also made from Belden Catsnake (8 conductors/4 pair). Belden has each pair shielded from the others and it uses dual rubber jackets for insulation, along with braided/mesh wire for RFI/EMI rejection.
Important Note: Belden Catsnake is stranded wire (to increase performance with high frequency signals), so trying to use it in many of the standard CAT6 plugs will not work. You need a plug that will allow you to pierce the conductors without any stray strands touching the other conductors (especially if you must strip the conductors to fit them in the plug. Considering the strands are about as small as a human hair, it’s hard to confirm this without a RJ45 tester. I am using the plugs recommended by Belden. Which are Belden R301602 (DATATUFF™ Industrial Ethernet Ruggedized RJ45) CAT6A Plugs. These plugs cost about $20 each, but they are rugged enough to last a lifetime, using nickel-plated zinc die-cast shielding and crimp terminations. Pay attention that the first fold down terminal is on the shielding for grounding.
When you go to crimp these connectors, for the grounding plate to lock, you need to put the pliers on the metal piece attached to the plastic strain relief. The metal will click into place, locking the grounding connection. Then you can push the plastic part with your thumb (usually) until it snaps as far as it can (it has 4 positions, depending on the cable width it will only go down so far). Once you have the black plastic piece holding against the rubber jacket, you are finished!
By using I2S instead of Coax, I will be able to natively decode DSD512 and will increase our PCM sample rate to 384kHz and beyond.
Since there are only 6 conductors I just pulled one of the twisted pairs out of the Belden Catsnake™. That is the easiest solution, but you have to keep this wire short and all the conductors need to be as close to exactly the same length for I2S to function error free.
This shows my logic that I went through in order to get the I2S order right on the first try. You can follow this and apply it to any order or any number of I2S ports (some have 8 I believe). Also note the actual pin order out of the punch down is not in numerical order, it’s in color order which is meant to make it easier, but it made it slightly harder IMO. Good luck to anyone with this project, I’d give it a 5/10 difficulty.
The obvious printed diagram is (the I2S line order) out of my FUN01 v1.1 XMOS module (Singxer SU-1 clone), so that is how it comes down the CAT6 Catsnake cable to the DAC. That is how you have to look at those values. Notice I made a numerical punch down order to the right of it to make it easier to follow. Then all that is left to do is to transfer these color and number matches to the funky order on our punch down block (sometimes called a Keystone jack). This is found to the left of the printed diagram with out of order numbers and 2 columns.
Note that this drawing (to the left of the I2S diagram for the FUN01) is exactly how the wires will be on the real hardware.