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Comment Re:Directional arrows aren't as silly as you'd thi (Score 1) 355 355

.That said, because these are network cables, that telescoping shield is irrelevant. You're not going to get ground hum into your amplifier from your network card, the way you would with a shield on an analog audio cable. They're simply not connected, and if they were, you'd have much bigger issues - like that hum causing all sorts of problems on your PCI bus. This is why network cable shields are typically connected at both ends: ground loops are irrelevant.

The ground loop formed by using ethernet over shielded twisted pair is not irrelevant if it corrupts the chassis ground which is also the shielded side of any singled ended signals like RCA audio. It would be very unlikely to affect the ethernet but it could sure screw up sensitive single ended signals.

Comment Re:Mod parent up. (Score 1) 355 355

From the cable tear-down, it does not appear that either end had any of the shielding connected to the plug shield.

I suspect the reviewer was not looking for this during the teardown and missed it if it was present.

With XLR cable connections, you have your shield, which IS connected at both ends, and your signal ground, which is isolated from the shield.

And equipment with XLR connections often has a "ground lift" switch to safely disconnect the ground and XLR ground isolators are available for equipment that lacks it.

Comment Re:Passed data with a ton of noise? (Score 1) 355 355

The article covered this. There was no continuity between the connectors through the shield but they did not test to see if the shield was connected at only one end:

It is also possible—I have no handy way to test—that they've tied the shield to one end only, though this would be highly nonstandard for network cabling."

Comment Re:Passed data with a ton of noise? (Score 1) 355 355

Idiot. A ground loop is *not* going to affect the quality of digtial audio delivered via an ethernet cable

This will almost always be the case however the problem is not with the ethernet signals being affected; it is with sensitive equipment like audio equipment at either end being affected. Balanced audio signals are commonly used where a single point ground cannot be guarantied and grounding a shielded cable at both ends would defeat this.

Comment Re:Passed data with a ton of noise? (Score 1) 355 355

Ethernet by definition isn't a grounded protocol. if you attempt to ground one end, you're going to fundamentally screw up 0 detection on the other. Both ends need to know where 0 is, and this is achieved by using a floating ground. Granted, since we're talking Ethernet anyway, any ground would be an earth ground and relatively close to each other. That statement is literally non-sense. You'd never use an earth ground on one side and a floating ground on the other. You never ground on one side and not the other. Plus, a "ground loop"? What the hell are you talking about? Ground is where 0 voltage is defined. To imply a loop, that would mean 0 on one side was connected to something other than 0 on the other, which would lead to a feed back loop which would cause all electronics connected to it to let the magic smoke out. You'd burn everything out if you tried to do such a thing. If you're concerned about grounding non-connected items, you use an earth ground, as it's a constant and not relative. As a power engineer I literally have no idea what you're talking about. You want all grounds in the system to be tied to a constant voltage. It doesn't matter what that voltage is, just as long as it's constant across all connected nodes. if they're not all connected and you want different ground voltages, then you have to use electric isolation, usually in the form of either magnetic or optical isolation. But Ethernet doesn't support either of those.

Ethernet is transformer isolated on both ends but if a shielded cable is used, then the shield connects to chassis ground on both ends. The problem occurs when chassis ground at each end differs which is not uncommon when dealing with the distances that long lengths of cable allow.

If a current flows through the shield then it couples to the ethernet signal lines but this would be unlikely to affect ethernet. When dealing with audio gear or sensitive instrumentation however, the ground current can cause problems whether it affects the ethernet interface or not and the common solution is to use an unshielded cable or ground the cable at only one end.

Professional audio gear uses balanced instead of single ended connections for audio to prevent ground loops; this is just an extension of that. It is also why USB and Firewire and not suitable in many cases unless a galvanically isolated interface is used.

Comment Re:like the lightbulbs that last virtually forever (Score 1) 175 175

"Crappy power" is not normal. Many western power grids have strict standards for voltage spikes, dips, sags, frequency errors, and THD that they will provide you. If you have crappy power it's because either your wiring is stuffed or you're running devices which are absolutely ancient (30 year old fridges make for some nasty power spikes), or have electronics which are failing / fake / never had the right certification to begin with and are spewing noise back onto your powerline.

- standards are great. You know what is greater though? How often are the standards met. Get back to us with metrics or you are talking about "in a perfect world...";
- lightning. 'Nuff said;

Which sums up were I live about 30 minutes west of St. Louis, Missouri. We get regular thunderstorms and lose power 2 or 3 times a year for hours and probably twice that often for seconds to minutes every year. Light bulbs including incandescent, compact florescent, and LED have half lives here of 3 to 6 months so the later two are not even close to economical no matter how much more efficient they are.

All of my computers, network gear, and test equipment is protected by online UPSes which has worked out well.

Comment Re:Moor? (Score 1) 175 175

DDR3 is about 10ns. If XPoint is 1000x faster than 5us NAND, then it has 1/2 the latency of DRAM. I doubt it, but you can see how it can easily be within a a factor or two.

I can believe it. Internally it operates like a static ram so there are no need for separate address strobes (although DRAM technically does not need them either) and no precharge.

Comment Re:Really? (Score 1) 483 483

"And here's a biggy. If you don't want Microsoft installing updates automatically -- if you're a user who has chosen to take control of this process up to now -- you probably will hate Win10."
Ok, here we have arguably the first real problem. MS has botched Windows updates in the past. Being able to block them and roll them back is how those situations have been limited and fixed. Lumping drivers into this forced upgrade schedule... as a laptop user this makes me nervous. Laptop drivers can be quite finicky and I don't always blindly trust newer versions when they land.

It only took one botched automatic update for me to disable automatic updates on all of my systems.

Imagine what happens when the power goes out, the UPS kicks in, the UPS software starts the orderly shutdown procedure, Windows starts installing updates in response to the shutdown, and the update process takes so long that the UPS runs out of power before Windows finishes so power is lost during the update procedure.

Comment Re:Disappointed (Score 1) 236 236

So you're saying it's impossible to do an arbitrary DC/AC to DC/AC without a massive efficiency penalty?

Efficiency is not so much as a problem as cost. It is easier to design converters with specific input and output voltages.

Converters commonly have a fixed output and 2:1 input voltage range which covers universal input power supplies with a 120 through 240 AC input . Converters with a 4:1 input voltage range are not as common but are available for a price premium. 10:1 input ranges are rare.

The problem with large input and output voltage ranges is that for the same power, the electronics have to handle both high voltage at low current and high current at low voltage making the design less optimal, less efficient, and more expensive.

Comment Re:solar powered? (Score 1) 236 236

There is no way to supply a high-power appliance (such as an AirCon) directly out of a PV array. None.

The panel is always operated at a point (MPPT) where it produces the most power, but that power is highly fluctuating whenever there's a slight obstruction in the incident sunlight (clouds, stray leafs, even passing birds).

You need a DC/DC power converter feeding a battery array. Then the DC appliance can be powered from that battery pack. Overall, an expensive solution mostly due to the need of local energy storage.

This is true in the sense that nobody bothers to make appliances which can be run directly from solar arrays. Air conditioners which use a variable speed drive instead of on/off operation could adjust their load to match the maximum power point of the solar array.

Comment Re:DC power? (Score 1) 236 236

RMS works fine for DC; it is just that for DC, the RMS and average are the same.

Coronal losses are some nonlinear function of voltage which becomes significant during the peaks of the AC voltage cycle at high voltages; lowering the peak to RMS ratio minimizes this for a given voltage.

Comment Re:200 times less field than your refrigerator (Score 1) 63 63

Your refrigerator, washing machine, and other household appliances run on inductive motors which use a thousand watts or so to generate electromagnetic fields strong enough to pull the magnets in the motor strongly enough to move 80 pounds of water and clothes. So those are electromagnetic fields in the kilowatt range.

Motors use as small a gap between the stator and rotor as is mechanically practical for best performance and this minimizes magnetic flux leakage.

Charging your phone requires around five watts or so. So the power levels, the amount of electromagnetic energy, is quite small - much smaller than the difference between a large washing machine and a small one.

Which is the opposite of how most inductive chargers work; they rely on loose coupling so that placement of the device to be charged is not critical.

Comment Re:Holy Jebus (Score 1) 220 220

The same trick works with double shotgun and rifle barrels. If there is a crack in the joint between the barrels, tapping them will yield a thunk instead of a ding because the crack causes loss in the reflected sound waves in the metal. The same loss in Q can be detected in a bell or other casting.

"Why waste negative entropy on comments, when you could use the same entropy to create bugs instead?" -- Steve Elias