Are my CAT5 and router my weak link?

To SGR,

I purchased my Opto-Isolator from Black Box (linked below). I am using the 100MB unit as it offers more than enough bandwidth for audio purposes but they do sell GB ones also.

http://www.blackbox.com/Store/Detail.aspx/Ethernet-Data-Isolator-10BASE-T-100BASE-TX/SP426A

By using one of these Isolators you are eliminating any noise from propagating beyond the point of its location. There is no need to rewire your LAN again.

For our purposes (Audio) CAT5 is more than sufficient in this configuration (with Isolator) because at the end of the day these other cables are offering nothing more than additional shielding from interference. The ones and zeros could care less about this interference unless its so severe as to cause them to no longer be the same ones and zeros at which point you obviously have other issues to worry about.

I have done some fairly through testing of this unit prior to using it in my own setup and found no difference in data transfer rates or ping times with the device Inline/Not Inline. I also conducted CRC Checksum testing of data that passed thru the Isolator verses the same data that was copied without the Isolator and found it was 100% the same in both cases.

Eniac, thanks for providing the info about the opto-isolator, which certainly seems like something that could be beneficial in many setups, and that apparently has no downside aside from its cost.

However, while it figures to be something that would eliminate groundloop-related noise, without further technical information on it (which I couldn't find via a Google search) I'm uncertain as to the degree of effectiveness it would have with respect to source-generated noise that may be riding on its input signal. For instance, some amount of stray capacitance will exist between the electrical parts of the device, that may to some degree allow noise to bypass the opto-coupler device. Also, I note that its intended purpose is described as surge protection.

Also, I would not necessarily conclude that it would make cable upgrade redundant, because the existing unshielded cables could conceivably radiate noise that would bypass the device. That could occur by radiation into the power wiring, or directly into system components or cabling. Bryon's experimental results would seem to support those possibilities.

Regards,
-- Al

Eniac,
Did you notice any difference in SQ?
If so what?

Hello Al, thanks for your response. The only detail I could dig up about this devices ability to reject current leakage across the optical isolation barrier was found in an article pertaining to the European Medical Device Directive (EN6060-1) which this product is said to comply with.

If your real bored and feel like reading it I have linked to the document below which talks about the allowable current leakage given a certain air gap distance which I can only assume this device complies with. From what I saw, the European standard allows for .5mA worth of Earth leakage & a .1mA enclosure leakage under normal conditions. Double that during an "Event".

Article can be found here:
http://www.newark.com/pdfs/techarticles/xpPower/MedicalPowerSupplies.pdf

SGR, In terms of the SQ differences I heard before and after the installation of the device I'm afraid that in my setup I heard no change under normal day to day listening.

I think I could here a slight difference under critical listening sessions (more air around the performers within the soundstage) but certainly not enough to convince any DBT subject.

Please keep in mind that in my setup previously described I have already gone to great lengths to minimize the propagation of noise via the LAN cables as much as possible even before the purchase of this device. In someone else's system the SQ differences may be far greater than my own if they haven't taken all the same precautions. One example of these precautions would be that I maintain at least a 3ft gap of separation between all of my various networking equipment and non of which share the same electrical outlet. This alone helps with any one noisy device from polluting the other which could ultimately compound the amount noise radiating thru or traversing down the Ethernet conductors toward your audio system.

Eniac, thanks for providing the link, which I read through. It doesn't seem particularly relevant, though, as what it is addressing is leakage current that occurs in response to the AC line voltage, at the AC line frequency. The concern here, of course, being mainly digital noise at very high frequencies. Also, since this device does not utilize any AC power, I suspect that its qualification against the EMDD is pretty much a formality, at least with respect to leakage considerations. Finally, I note the statement that:

Reducing leakage current within a power supply usually means eliminating or limiting the value of Class Y filter capacitors from live-to-earth and neutral-to-earth. It also demands that stray capacitance to earth is minimised through careful design. Unfortunately, the overall effect of these measures tends to compromise EMC performance, although minimising stray capacitance can reduce common mode noise.

So in the kinds of designs being discussed in the paper there can be a tradeoff between minimization of AC leakage and optimization of EMC (Electro-Magnetic Compatibility, referring to the effects of radiated interference).

That said, as I indicated earlier the device does seem like something that can be beneficial in some systems, and that has no apparent downside apart from cost. Thanks again.

Regards,
-- Al