Well, actually I don't technically have that minor - was a semester shy when I dropped it - but, well, close enough I suppose.
I will disagree. I have seen some evidence that DA equilibrium can change rather slowly over time depending on average operating conditions. Please consider that DA can be modeled as an RC ladder network, which I think is uncontroversial. Some of the RC time constants of that ladder can be longer than the time over which typical measurements are usually taken. If it changes over a longer time than modeled it may appear as non-time invariant according to the model. IME something like one or two weeks to settle to a very low level for polypropylene. All it takes is to put a FKP cap on a pin header in a dac Vref supply (with zero PSRR), give it a couple of weeks, then suddenly reverse its polarity. You can't hear that? On my system the effect is clearly audible, even if some people don't consider it a big effect. I'm not claiming its big, only that it can be audible on some systems.
Have you read Kahneman's book from cover to cover and looked up the references to read the original research? Haidt? Nisbet? Tetlock? Other's?
The moon causes things to change slowly over time (like tides) I've not seen anyone planning their listening around a tide chart.
like that is going to happen in real life. Try coming up with a real work scenario.
According to dictionary invariance is the property of remaining unchanged regardless of changes in the conditions of measurement. So 'Time invariance of DA equilibrium' means that DA equilibrium does not change over time. Shouldn't this be desirable? Or is this another example of audiophile mumbo jumbo?
What happens is that people sometimes try to choose caps for audio use by listening to what the caps do to the sound. Often they don't leave the caps in place long enough to know what they will sound like after some longer time. So it may be something people in a cap thread would want to know about.
you said "then suddenly reverse its polarity" is audible, nothing about leaving it in place being audible.
In engineering 'time invariance' means the equation describing the electrical properties of a device does not changer other than as a function of time, f(t). The differential equations are 'linear' so long as that condition is met. For example, i=C dV/dt is linear, but sometimes its really more like I = C*dV/dt + dC/dt*V which is a model of a time variant capacitor still modeled as a function of time. But a model can also become quite nonlinear if C changes as a function of something other than time, say, such as it's prior state (i.e. it has a memory, it varies with temperature and heat flow, etc.).
The point is that such equations used by EEs are always merely models of devices. We try to use the simplest model that's good enough for the problem at hand.
A real capacitor changes in more than one way with time. There is sort of what might be called a 'burn in' followed by slower drift (in various parameters), then eventually leading to wear out or failure. In addition to that some film caps which can take a couple of weeks to settle starting from when they are new, might only take one week to settle after the first polarity reversal. So, in reality there is 'non-time invariance' for the purpose of how EEs model and think about capacitor behavior, if we want to get more nit picky about it.
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That is incorrect. See e.g.
https://ptolemy.berkeley.edu/eecs20/week9/timeinvariance.html
https://www.tutorialspoint.com/signals-and-systems-time-variant-and-time-invariant-systems
"A time-invariant system is one whose behavior (its response to inputs) does not change with time."
"The property of a system which makes the behaviour of the system independent of time is known as time invariance."
https://ptolemy.berkeley.edu/eecs20/week9/timeinvariance.html
https://www.tutorialspoint.com/signals-and-systems-time-variant-and-time-invariant-systems
"A time-invariant system is one whose behavior (its response to inputs) does not change with time."
"The property of a system which makes the behaviour of the system independent of time is known as time invariance."
A time invariant system does not change with time. Real devices are non-time invariant. Did I make a typo somewhere?
I = C dv/dt is a time invariant model so long as C is a constant.
I = C dv/dt is a time invariant model so long as C is a constant.
The second one is more interesting, wrt the first one, I don't know if we should really blame a manufacturer for including a solution to a (potential) problem, even if it is a simple one, like a resistor though.
Hi Jakob, not seen you for a while. I don't blame them for offering a solution, more the marketing that gets wrapped around it. Mind you not aware of anyone implementing this with normal capacitors so is there a real problem?
The equations in the first patent attached to post #78 are full of dimensional errors, by the way: time being equated to time squared, and resistances being subtracted from inductances. Right...
@MEGB1262,
can't comment on the audiosciencereview-thread, but in the 80s we did our first steps using controlled listening tests (described in other threads in more detail) when trying to find out if differences between various foil caps could lead to audible (means perceptible) differences, but we tried them as coupling capacitors between an MC head amp and the next stage, so regarding the signal levels a quite different application.
At that time quite ordinary industrial capacitors, one a polyester and the other made from metalized polypropylene foil; audible differences (most likely 🙂 ) existed, later I read Colloms take on passive components, learned about the first capacitors or audio purposes (Wondercap and Sidereal) and gave these another try, this time as a coupling capacitor in a line level application compared to a jumper.
Conclusion was as all these capacitors had a perceptable impact, it would be better to avoid them all, which obviously opened another can of worms. 🙂
Beside that, IMO price matters, some of these caps are quite expensive; wouldn't it worth to think spending the same amount on better drivers or other things? If it is a cost no object project, then I'd say, buy a few from the smaller values from the lines and do some listening to find out if it matter to you .
Sometimes it is not so easy to find out which procedure (wrt evaluation by listening) suits best, but maybe we can help in this regard.
can't comment on the audiosciencereview-thread, but in the 80s we did our first steps using controlled listening tests (described in other threads in more detail) when trying to find out if differences between various foil caps could lead to audible (means perceptible) differences, but we tried them as coupling capacitors between an MC head amp and the next stage, so regarding the signal levels a quite different application.
At that time quite ordinary industrial capacitors, one a polyester and the other made from metalized polypropylene foil; audible differences (most likely 🙂 ) existed, later I read Colloms take on passive components, learned about the first capacitors or audio purposes (Wondercap and Sidereal) and gave these another try, this time as a coupling capacitor in a line level application compared to a jumper.
Conclusion was as all these capacitors had a perceptable impact, it would be better to avoid them all, which obviously opened another can of worms. 🙂
Beside that, IMO price matters, some of these caps are quite expensive; wouldn't it worth to think spending the same amount on better drivers or other things? If it is a cost no object project, then I'd say, buy a few from the smaller values from the lines and do some listening to find out if it matter to you .
Sometimes it is not so easy to find out which procedure (wrt evaluation by listening) suits best, but maybe we can help in this regard.
Life got in the way, but I'm glad to see the usual suspects still being around. 🙂
I agree that in many applications it will not be a problem, but sometimes it surely can be.
This thread which was recently resurrected for all the wrong reasons is now closed to further replies.
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