Well;
but obvious and measurable explanations why it can be audible are massively ignored in order to offer artificial explanations including "reverberation by DA" and other "pulse test" miracles.
Please Wavebourn put some numbers on it, separate out components you would never use, High K ceramic, electrolytic, etc. from a long list of good ones, among the good ones the differences are so trivial the claim that the differences are 100% obvious are suspicious.
To claim a 100% ability to tell the difference between PP an PS in an RIAA requires more that asking your audio buddies what they think.
I mean 99% ability to tell the cause of the effect. That is most often non-linear impedances coupled by innocent caps.
Nobody that I know would give a 100% opinion about 2 similar caps. However, WITH LISTENING TIME, using one sort of cap or another, an opinion MIGHT be formed. And then future decisions might come from there.
I proved that the differences between a good polystyrene, Teflon, or polypropylene cap are as close, or closer than 0.002%, with the 'asymmetric pulse test', so how could they sound OBVIOUSLY different with a casual listen? However, construction compromises for an individual cap type and brand, MIGHT be important for a variety of reasons. This is what I was asking Richard Marsh about. He HAS the experience designing caps, more than anyone here, certainly.
I proved that the differences between a good polystyrene, Teflon, or polypropylene cap are as close, or closer than 0.002%, with the 'asymmetric pulse test', so how could they sound OBVIOUSLY different with a casual listen? However, construction compromises for an individual cap type and brand, MIGHT be important for a variety of reasons. This is what I was asking Richard Marsh about. He HAS the experience designing caps, more than anyone here, certainly.
John;
I also confirmed many times, both by listening tests and experiments, that the more linear impedances couple caps, the less they are "audible". Also, it is valid for shunt caps: when they shunt something highly non-linear requirements to their quality are higher. For example, PS caps in class AB amps are very "audible". Fortunately we have lots of options to choose from, depending on the application. The Only Cap for all applications does not exist, since requirements are contradictory.
I also confirmed many times, both by listening tests and experiments, that the more linear impedances couple caps, the less they are "audible". Also, it is valid for shunt caps: when they shunt something highly non-linear requirements to their quality are higher. For example, PS caps in class AB amps are very "audible". Fortunately we have lots of options to choose from, depending on the application. The Only Cap for all applications does not exist, since requirements are contradictory.
The caps from base or gate to ground. I haven't found a measurement correlation on this but maybe haven't look hard enough. Maybe they were not the correct caps. Richard made me a believer in good caps many years ago when he was at MIT especially with speaker caps, like anything the best cost $ but if you want to win at the races...
It does qualify as religion, a belief in one's experience. A theory thought in the mind or acted upon is thought or acted as an experience. There exists no other form of "theory." They're beliefs too with their own chapters and verse.
Their sound is obvious to me also, John, not entirely but fairly unmistakeable.
Strictly speaking Q=CV may only be true for a constant capacitance, but it is nearly true for real capacitors which are approximately constant.
As a capacitor charges up it can change capacitance, whether through mechanical movement or changes in the dielectric permittivity. Both of these changes are likely to be symmetric with respect to voltage, so if +10V causes a 0.5% increase in C then -10V will also cause a 0.5% increase.
If a positive signal peak is treated in the same way as a negative signal peak (i.e. the capacitor has a symmetric or even response to voltage) then the signal will suffer odd-order distortion. The order of signal distortion will be one greater than the order of capacitor non-linearity. (The same rule applies for resistors: a linear (e.g. first-order) resistance change with voltage would cause second-order distortion to the signal.)
Permittivity vs. electric field. The curve is usually symmetric about zero electric field, and typically rises with electric field.
Not quite done...
I measure (and make) inductors quite a bit, and always have to consider proximity effect. Generally, I use the Ls/Rs model. It is important to get the Rs for dissipation as well as amp stability (in my app, the load is the inductor.)
Solid wire suffers proximity effect big time through the audio band, and I don't have a good model for it. Using multiple inductors and resistors in a ladder are not the same as that model still stores energy... whereas proximity effect does not. It is a frequency dependent resistor.
Foil inductors are the exact same, albeit the mechanism behaves a tad differently..as frequency increases, the current distribution still changes, but it changes along the axis.
Currently I'm using #13awg equivalent litz with 150 strands...these puppies are rock solid way beyond 20Khz both inductance and resistance. But that wire is a PITA to use.
Foil capacitors can do the exact same thing, but axial changes in current distribution of the foil will cause a lowering of the capacitance, as some of the dielectric will actually "starve", become unavailable to the current as a result of proximity effect on the foils. This is of more significance with jellyroll construction when the end leads are on opposite ends of the foils as it enhances the solenoidal magfield.
I seem to recall either JC or Malcolm Hawksford relating a story about a cap guy who had a better cap using slits in the foil, but no valid explanation for why (IIRC).
jn
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Wayne, I didn't get your exact question, BUT as you know, I use cascodes, these days, in most of my designs. The main reason for using a cascode in my input stages is to extend the range that it can operate. I use jfets, mosfets, or bipolar devices, depending on the budget for the design, primarily.
I prefer jfets for the cascode part if possible.
There are 2 ways that I make a cascode. The most elegant is the folded cascode. That is used for the CTC Blowtorch preamp, Vendetta Research input stage, and the Constellation phono stage, all my very best efforts.
Normal or vertical cascodes are used in my power amps and for the JC-2 preamp, etc., primarily to extend the voltage hold-off of the input devices. However, of course, there are secondary reasons for using cascodes as well.
Now, to your question: I presume you wonder if or why I would put a fairly large value cap at the base or gate terminal (through a 100 resistor, of course) of the vertical cascodes, such as in my power amp designs, and why? I do it to buffer any noise that could possibly come from the power supply as well the noise generated by the voltage dropping resistors. Is it absolutely necessary? Maybe not. Some of my cheaper amps don't use these bypass caps just to save parts count. Some of my most expensive folded cascode designs do not use bypass caps either, for other reasons. There is no easy answer.
I prefer jfets for the cascode part if possible.
There are 2 ways that I make a cascode. The most elegant is the folded cascode. That is used for the CTC Blowtorch preamp, Vendetta Research input stage, and the Constellation phono stage, all my very best efforts.
Normal or vertical cascodes are used in my power amps and for the JC-2 preamp, etc., primarily to extend the voltage hold-off of the input devices. However, of course, there are secondary reasons for using cascodes as well.
Now, to your question: I presume you wonder if or why I would put a fairly large value cap at the base or gate terminal (through a 100 resistor, of course) of the vertical cascodes, such as in my power amp designs, and why? I do it to buffer any noise that could possibly come from the power supply as well the noise generated by the voltage dropping resistors. Is it absolutely necessary? Maybe not. Some of my cheaper amps don't use these bypass caps just to save parts count. Some of my most expensive folded cascode designs do not use bypass caps either, for other reasons. There is no easy answer.
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