Popular Post AMP Posted July 12, 2018 Popular Post Share Posted July 12, 2018 Darryl, The issue with shielded Ethernet is that the shield has the potential to connect the ground plane of the audio device to the ground plane of whatever it's connected to. This gets especially bad with switches that use a wall wart power supply as they do not have a real connection to earth. In that case the audio component's ground becomes the ground for the network device and potentially anything else connected through that network device. It gets ugly from a noise perspective. If I recall correctly, you're using a JCat Ethernet card in your server (which has a shield connection to ground), but I can't remember the type of power supply that it has. If it's the traditional internal power supply with a 3-prong plug to the wall then there's a possibility that the server and bridge are seeing two different ground potentials and that leading to a current being developed between the ground planes of the two devices. This can lead to a hum, but that more commonly happens when unbalanced connections are used since signal and reference ground share the same wire. Based on the rest of your system I'm guessing that you're using balanced connections. If your server has an external power supply that connects with the typical barrel connector (whether the power supply is grounded or not) then the Bridge is likely acting as the ground reference for the server. This typically doesn't lead to hum, but it's possible. In either case, we recommend against using shielded Ethernet cables as the shield is a very easy way for noise to get onto the ground plane of the audio system. This is especially bad when dealing with digital as that noise can create some issues both on the digital and analog sides. The noise may not be audible, but it's definitely within the current differential between a couple of bits. In other words, you may not be able to hear it, but it may be messing with the overall resolution of your system. Different Ethernet cables (the audiophile variety) deal with shielding differently as none of them follow the actual standard, so it's hard to predict how one is going to behave over another. Sadly, most manufacturers of audiophile Ethernet cables demonstrate little understanding of how Ethernet actually works which makes many of the expensive Ethernet "solutions" suspect at best. Hum is typically generated by either a difference between the ground potential of two or more components in the system or it's some noise that's being picked up by the cables. Ground loop noise can usually be isolated by methodically disconnecting components from the system until the hum goes away. Start with the Ethernet cable. If the hum is gone then there's your culprit. Another possibility is that your amps are on a different outlet than the rest of the system. Again, if you're running balanced this typically isn't an issue but it's worth doing a bit of cable work to try to get the amps and components on the same outlet. My guess is that you have an interconnect that's picking up noise from a power cable or transformer in one of your components. This happened to me recently and it was due to an interconnect getting a bit too friendly with a couple of power cables. A little bit of rearrangement solved the problem. I've also seen this happen when the excess length in an interconnect is coiled up underneath a rack or amp stand. On the amp side it can pickup noise from the transformers and on the rack side the bottom shelf is the typical spot for a power conditioner which can be a big source of EMI. Russ, The Computer Audiophile and Pale Rider 1 2 Programme Manager, Streaming Audio Data Conversion Systems, Ltd Link to comment
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