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needsp  
#1 Posted : Wednesday, May 10, 2017 9:22:19 AM(UTC)
needsp

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Hi

I have an Amanero USB to i2s converter with Cronus, Hermes and Rhea. Until now I connected this with a very short cat 5e cable to my Buffalo 2 via a RJ45 socket and a 2:1 mux. I also occasionally use a SACD player connected in the same way. It worked perfectly.

Yesterday I decided to install the Teleporters I bought years ago, to make it possible to use the converter more remotely, and just to adopt the most robust approach possible. So I installed a (v1.2) teleporter in the Converter module, and a (v 1.1) teleporter in the SACD player. It didn't work, no lock at all! I checked and rechecked my work, but all seemed fine, and I know you test all boards before dispatch.

I checked the support pages and found some reference to issues with the relative potential of transmitting and receiving compound grounds, and a description of the difference between v 1.1 and v 1.2 of the teleporter. I ran a wire between the Converter module's ps ground and buffalos' ground- which is connected to mains earth- and everything worked perfectly. (There is just this single earth connection to buffalo at its input. The spdif input is transformer coupled, and I use the balanced outputs which feed line input transformers in my preamp.)

What's the best way to resolve this issue long term? I'm surprised more people haven't reported this issue. Many source components will be unearthed category 2 devices- such as my SACD player- or powered by by floating power supply like my Amanero ( I use an iFi supply). I thought the best approach would be modify my v 1.1 teleporter to use a screened rj45 connector, ground this and the transmitters' v 1.2 connector locally, and use a shielded cat 5e lead between the two. Do you agree, or is there a better approach?

Many thanks

Paul Needs

Edited by user Wednesday, May 10, 2017 1:40:11 PM(UTC)  | Reason: Not specified

Brian Donegan  
#2 Posted : Wednesday, May 10, 2017 5:39:18 PM(UTC)
Brian Donegan

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This use case is why we updated the Teleporter to use a shielded ethernet connector. It is not always a problem, but can be.

You could use shielded ethernet cable and manually connect the ground on the v1.1 side, or replace the connector and jumper the ground to it (as you suggest).
needsp  
#3 Posted : Wednesday, May 10, 2017 6:04:57 PM(UTC)
needsp

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Hi Brian

I noticed that the v 1.2 connector isn't connected to ground on the board. I can jumper it, but why not connect it in the first place?

Do you mean to connect the screen or ground at both ends, or just at the day? My understanding indicates both ends, but this breaks the isolation. But I guess it the robustness of the differential signal which is the key thing here.

Thanks

Paul
Brian Donegan  
#4 Posted : Wednesday, May 10, 2017 6:18:07 PM(UTC)
Brian Donegan

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You add a solder blob or jumper at J2 to connect it to ground. It's an optional connection.
thanks 1 user thanked Brian Donegan for this useful post.
needsp on 5/12/2017(UTC)
needsp  
#5 Posted : Wednesday, May 10, 2017 6:32:45 PM(UTC)
needsp

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Hi Brian

But should I connect the screen or ground at both ends, or just at the dac ? My understanding indicates both ends, but this breaks the isolation. But I guess it the robustness of the differential signal which is the key thing here.

Thanks

Paul
needsp  
#6 Posted : Thursday, May 11, 2017 7:08:12 PM(UTC)
needsp

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Hi

Fitted a screened rj45 connector to the dac's v 1.1 teleporter and used a screened cat 6a cable between it and the Amanero's teleporter. As I expected I needed to connect the screen to local ground at both ends to get a lock, by equalising source and dac's ground potentials- screening as such in my setup is incidental. It's rock solid- l tried it with a 15 m cable and it worked perfectly. Thanks Brian!

BTW when I posted about the floating connector housing I hadn't noticed J2, added to v 1.2

This has been a useful experience- I now know exactly what LVDS is, and why the relative levels of the two common mode potentials, if too different, can interfere with the differential signal transfer

Paul
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