The truth about EMF and electron flow of power

[grapplesaw]

Ok I often mention inductance in supply wires and direction of signal wires in your amp. I think this would be a good place to have us contribute to the truth of how elections flows and how it affects surrounding Components and signals.
Does shielding work better than proper routing?
Do braided wires flow differently than solid?
How much effect does shielding have on EMF and residual noise?

This is a start so please join in with answers and questions.

To kick it off , and reason to start this thread I watched this video and has got me thinking what if. It sauces a lot that if true is quite interestin.


I hope some of you who know or question the subject can add to answer what are the the best practice in wiring and their effects on electric flow.
Enjoy

 

[mlucitt]

Electricity, or Electromotive Force (EMF) is a squishy subject. Direct Current (DC) is one thing, Alternating Current (AC) is completely different. And in the form of AC, EMF will exhibit dramatically different characteristics depending on the Frequency.

Some examples:
Ohm's Law is different for AC than it is for DC (there are actually two Ohm's Law charts).
If you receive a great enough shock - DC will "Hold" you and AC will "Throw" you. Maybe.
The old saying - "Its the Volts that jolts, but its the Mills that kills." So the shock from a Spark Plug could be 15,000 Volts, but only 10 milliamps - not deadly. But a shock from a 120 Volt source at 10 Amps could very well be fatal. Only 15 milliamps across the chest cavity could lead to fibrillation, less than a LED. Forget about a fuse protecting you from danger.

I like shielding when I am trying to protect low-level signal wires from high-energy sources of low frequency Electro Magnetic Interference (EMI) and high frequency Radio Frequency (RF) noise caused by electromagnetic induction, electrostatic coupling, or conduction. Proper routing is important too. But there are relationships (and complex formula) between the distance of the wires, the size of the conductors, the amount of current flow, and too many other variables to consider. So we route the Power, Ground, and Signal wires appropriately (including crossing them at 90 degrees) to minimize the EMI and RF "trash".

With 60Hz AC in our Power Supply, we do not have to deal with EMI or RF interference internal to the audio equipment. But external sources can become problematic because they operate or produce noise in the electromagnetic spectrum anywhere from about 9kHz to 300GHz. Recently, a customer complained of "Hash" or crackling coming from his newly WOPL'd amplifier. It turned out to be harmonics from a Switching Power Supply in a Wi-Fi Range Extender plugged into an outlet in the next room. Likely, this interference was conducted through the house wiring, but his Furman Power Conditioner was not able to stop it. It could also have been induced by RF interference in the cables or the unshielded power cord.

This is a good topic. But I prefer to use Best Practices rather than spend any effort on the why or experimentation.

 

[J!m]

There are published charts for frequency range of a/c in solid conductors.

I always wondered about cable, where a single “conductor” is comprised of many smaller conductors.

But I use solid wire (not stranded) in my phono pre and also used it in a (never worked) passive buffered preamp.

All power runs are 90 degrees any signal and as far apart as possible. Keeping signal lines away from one another might help with crosstalk, and might not, but it’s easy to keep it seperated.

 

[Rat44]

Just starting out in the ham radio field.
So far I have been plagued by lots of RFI issues.
EMF can be caused by improper cable runs.
Or the use of the wrong cable or wire.
I use VHF a lot and it is very susceptible to these issues.
so far in my world wallwarts and LED lights are the biggest offenders.

 

[J!m]

Those CCFL lights are noisy as hell too- combination of fluorescent and LED switching power supplies.

 

[George S.]

https://forums.aaca.org/topic/388502-positive-vs-negative-ground-is-there-an-engineering-reason/