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
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
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.
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.
Hi,
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,😉
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,😉
Konnichiwa,
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
SY said:
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
Re: Re: Linearity
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
MBK said:
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
Nope. Experimentallly well-known. See Ian's post.
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.
Re: Re: Re: Linearity
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.
IanHarvey said:
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.
Re: Re: Re: Re: Linearity
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 said:
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
Re: Re: Re: Re: Re: Linearity
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.
jh6you said:
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.
Re: Re: Re: Re: Re: Re: Linearity
Oh boy, Relays. I actually know something about that this.
Relays are catagorised as either being power relays or small signal relays (or both, but you have to pick one mode and never use it for the other).
Power relays have silver alloy contacts that tarnish (oxidise) which increases contact resistance. At some current level, electron flow has a cleaning effect on the contact which removes the tarnish. Below that current flow, the contact is not cleaned and the contact becomes unreliable.
Small signal relays have a noble metal coating over the silver alloy contacts (usually gold) which prevents tarnishing and oxidation. The problem is that the gold coating is very thin and if you ever pass too much current through the contact the gold plating is destroyed and the relay is no longer reliable for small signal use.
This is why relays have both a minimum and a maximum current rating. The maximum rating is how much it can safely handle and the minimum is how much current is required to keep the contacts clean.
So yes, outside it's ratings a relay is a non-linear device. However this is only over a fairly long time scale. If you are passing an AC signal through a relay there is insufficient time for an oxide coating to form during the zero crossing.
Phil
MBK said:
MBK said:
Oh boy, Relays. I actually know something about that this.
Relays are catagorised as either being power relays or small signal relays (or both, but you have to pick one mode and never use it for the other).
Power relays have silver alloy contacts that tarnish (oxidise) which increases contact resistance. At some current level, electron flow has a cleaning effect on the contact which removes the tarnish. Below that current flow, the contact is not cleaned and the contact becomes unreliable.
Small signal relays have a noble metal coating over the silver alloy contacts (usually gold) which prevents tarnishing and oxidation. The problem is that the gold coating is very thin and if you ever pass too much current through the contact the gold plating is destroyed and the relay is no longer reliable for small signal use.
This is why relays have both a minimum and a maximum current rating. The maximum rating is how much it can safely handle and the minimum is how much current is required to keep the contacts clean.
So yes, outside it's ratings a relay is a non-linear device. However this is only over a fairly long time scale. If you are passing an AC signal through a relay there is insufficient time for an oxide coating to form during the zero crossing.
Phil
Thanks Phil,
nice to have a clear and definitive solution to that one! I was really wondering what to make of these relay specs...
nice to have a clear and definitive solution to that one! I was really wondering what to make of these relay specs...
Re: Re: Re: Linearity
...or inductance which changes with current. Such as any inductor based on a core material that does not exihibit a linear BH curve (Like most used for inductors and transformers).
Also the nonlinearities depend on the domain you're in. If you're looking at a time domain of a single frequency, what you say may be true. However, if looking at frequency domain, the parasitics can wreak havoc... ...the L's and C's become frequency dependent, thus nonlinear depending on frequency. Think of why you don't use speaker cable to transmit Radio frequency energy!
-Dan
IanHarvey said:
...or inductance which changes with current. Such as any inductor based on a core material that does not exihibit a linear BH curve (Like most used for inductors and transformers).
Also the nonlinearities depend on the domain you're in. If you're looking at a time domain of a single frequency, what you say may be true. However, if looking at frequency domain, the parasitics can wreak havoc... ...the L's and C's become frequency dependent, thus nonlinear depending on frequency. Think of why you don't use speaker cable to transmit Radio frequency energy!
-Dan
Re: Re: Re: Re: Linearity
Not sure I understood this bit. You can vary any parameter you like with frequency; just so long as it obeys the 'superposition' principle, its effect will remain linear.
(The main problems with using speaker wire for RF outputs is the difficulty of getting stuff of the right characteristic impedance which terminates neatly into commonly used connectors. Consider the use of a bent wire coathanger as a TV ariel - it's not even sold for its electrical properties, but conveys a useful amount of signal even at >400Mhz).
Cheers
IH
dkemppai said:
Not sure I understood this bit. You can vary any parameter you like with frequency; just so long as it obeys the 'superposition' principle, its effect will remain linear.
(The main problems with using speaker wire for RF outputs is the difficulty of getting stuff of the right characteristic impedance which terminates neatly into commonly used connectors. Consider the use of a bent wire coathanger as a TV ariel - it's not even sold for its electrical properties, but conveys a useful amount of signal even at >400Mhz).
Cheers
IH
Actually, there's a lot of zip cord that has a characteristic impedance of about 75 ohms- as a teenager, I found that useful in emergencies for hookup to my 40 meter dipole. And a few of us oldsters will remember 300 ohm twin lead, which is constructed like zip cord (PVC extruded over stranded copper), but with the conductors further apart. Worked well at a few hundred megahertz.
Flattened Not Plaited....
Naim amplifiers specify Naim speaker cable (NAC-A5) which looks like oversize 300 ohm TV aerial ribbon cable.
By definition this is relatively highly series inductive and very low shunt capacitive, and indeed Naim amplifiers require this inductive loading to ensure stability - overly capacitive cables will cause Naim amplifiers to oscillate.
Naim NAC-05 Page
Owners who say that cables DO make a difference
Naim saying that cables Do make a difference
Eric.
Naim amplifiers specify Naim speaker cable (NAC-A5) which looks like oversize 300 ohm TV aerial ribbon cable.
By definition this is relatively highly series inductive and very low shunt capacitive, and indeed Naim amplifiers require this inductive loading to ensure stability - overly capacitive cables will cause Naim amplifiers to oscillate.
Naim NAC-05 Page
Owners who say that cables DO make a difference
Naim saying that cables Do make a difference
Eric.
Attachments
noise and nonlinearities
Speaking about nonlinearities - does noise have any well defined relationship to signal level? For all I know, voltage noise and current noise in resistors is related to R and to f. Incidentally such constant, amplitude-independent noise would then be a nonlinear effect in such a simple thing as a resistor... or not?
Anyway - listening to actual recordings I sometimes have the impression that with rising amplitude the signal - say, a loud piano note - is like "enveloped in a noise cloud". That of course may be a) an illusion b) derive from active components (rather than passive ones).
Anyway if the noise would truly rise with amplitude it could at least possibly do so linearly ... yet if this is so, then that would complicate the assessment of real world S/N ratios enormously, wouldn't it?
Speaking about nonlinearities - does noise have any well defined relationship to signal level? For all I know, voltage noise and current noise in resistors is related to R and to f. Incidentally such constant, amplitude-independent noise would then be a nonlinear effect in such a simple thing as a resistor... or not?
Anyway - listening to actual recordings I sometimes have the impression that with rising amplitude the signal - say, a loud piano note - is like "enveloped in a noise cloud". That of course may be a) an illusion b) derive from active components (rather than passive ones).
Anyway if the noise would truly rise with amplitude it could at least possibly do so linearly ... yet if this is so, then that would complicate the assessment of real world S/N ratios enormously, wouldn't it?
- Status
- Not open for further replies.