I don't believe cables make a difference, any input?

[Christopher]

Hi Ian

I'd just like to make sure I understand this.
A device under this definition of linear attenuates a given frequency by the same quantity, regardless of what other frequencies are mixed with it?

Chris

[SY]

Yes, it's called "superposition." It's a general feature in physics.

The regimes where this wouldn't be applicable to wire would include wire that is being heated or cooled during the measurements, wire that is changing L,C, or R during the measurement, and wire coupled to a non-time-invariant generator during the measurement. For all practical purposes, wires ARE linear networks.

[fdegrove]

Hi,

Ummm... maybe physical (real) resistors, capacitors, inductors etc., are not as linear

Let me assure you that non of the above components are linear in any way...some worse than others.

Some cables be have more linearly than other as well, mostly depending on the interaction between their own non-linearity and speaker/interface linearity.

Which goes some way into explaining why some of us do hear differences amongst various cables.

Cheers,

[fdegrove]

Hi,

If anyone ever needs an example of a funny typo:

be have

Should read "behave".

My apologies,

[ThorstenL]

Konnichiwa,

Originally posted by SY
For all practical purposes, wires ARE linear networks.

You present a supposition, a thesis, as fact.

If, for all practtical purposes wires are linear networks there is no need to produce silverplated cables, cables with foamed PTFE insulation, Cables with a foil & basket weave screen, cables with solic core twisted pairs for longs runs of computer networking cables etc.

So, not only are you presenting a thesis as fact, your thesis is full of holes, so full actually that not much thesis is left.

Sayonara

[IanHarvey]

Originally posted by MBK



Ummm... maybe physical (real) resistors, capacitors, inductors etc., are not as linear and time invariant as ideal ones?

No, they're not. The point is that many imperfections are themselves linear - parasitic capacitance across inductors, lead inductance & series resistance in capacitors, and their effects are therefore measurable in terms of frequency response & phase.

You cannot create nonlinearities by adding parasitic L's, C's and R's about a component - it requires something more exotic (such as capacitance which changes with applied voltage).

Cheers
IH

[SY]

You present a supposition, a thesis, as fact.

Nope. Experimentallly well-known. See Ian's post.

If, for all practtical purposes wires are linear networks there is no need to produce silverplated cables, cables with foamed PTFE insulation, Cables with a foil & basket weave screen, cables with solic core twisted pairs for longs runs of computer networking cables etc.

None of these techniques have any significant relationship with nonlinearity. See Ian's post. Unless you're idiosynchratically defining shielding as "nonlinear." And since you bring it up, see the fundamental papers done by my good friend Chakra Gupta on foamed PTFE (for example, his review chapter "Fluoropolymer Foams" in Klempner and Frisch, "Handbook of Polymeric Foams and Technology," Hanser, 1991) - he pioneered the method of making and processing foamed fluoropolymer insulation for wires, and covers in great detail the reasons for doing so. Nonlinearity doesn't seem to pop its head up.

[MBK]

Originally posted by IanHarvey


... many imperfections are themselves linear - parasitic capacitance across inductors, lead inductance & series resistance in capacitors, and their effects are therefore measurable in terms of frequency response & phase.

You cannot create nonlinearities by adding parasitic L's, C's and R's about a component - it requires something more exotic (such as capacitance which changes with applied voltage).

Cheers
IH

Well, honestly, I can easily imagine true non-linearities in any physical object. Think speaker drivers and air. Obviously nonlinear. Now think conductors and electrons. Why would it be any different? Linearity is a mathematical ideal that works as a very good approximation, yet the real world is only represented by math *models* - it is not itself a math model. Mathematical results ever only truly apply to math itself. All else is modeling. Not to speak of complexity theory: unpredictable, unmodelable nonlinearities at the core of life itself.

Back down to Earth now:

Example 1. Say, a capacitor has a manufacturer's specified rating. Why the rating ? - because outside that rating the mathematical approximation is a bad one. Even the "parasitic R and L" component is a simplistic model of a real cap. And, if high voltage zaps a cap, it's a decidedly nonlinear breakdown. Not hard to imagine how the cap could become nonlinear way before the actual breakdown.

Example 2. A confusing one for me. In relay specs I read not just a maximum rated V and I, but also a minimum rated V and I. That makes me uncomfortable: does that mean now that under AC, that contact will actually have a nonlinear behaviour at the zero crossing? It seems so. And this is just an ideal zero resistance contact we're talking about.

[jh6you]

Originally posted by MBK

Example 2.

I don't understand very well what you talk about.
Maximum rating might mean the stable operation point, while
minimum rating mean the minimum holding point (or maximum reset point).

JH

[MBK]

Originally posted by jh6you


I don't understand very well what you talk about.
Maximum rating might mean the stable operation point, while
minimum rating mean the minimum holding point (or maximum reset point).

JH

The ratings are for the signal portion, not the coil portion. For those relays (signal level of course) where these data were given the maximum rating was typically around 125V, 1 A, the minimum rating about 1-10 mV, 10 uA.