What I said before (syn08 commentad that as a BS) DA itself is not a direct source of non-linear distortions, but it's presence often correlates with presence of non-linear distortions, also being used between solid state stages with non-linear input and output resistances it causes non-linear distortions indirectly, being involved in the signal path.
john curl said:
John,
I did it before here, and I'll do it again if required, although I realize the chances to get through your wall are minimal. But meantime, let me remind you a few things:
The work and model you mentioned is addressing a linearized model of DA. From this perspective, there's nothing wrong with this work; the only fundamental problem is that it has NOTHING specific to DA. Each and every lossy mechanism in a reactive device can be modeled in this way, in particular e.g. a capacitor ESR. You have absolutely no way to distinguish between the DA contribution and any other lossy contributions, external or internal to the material. In fact, what the work you mentioned is demonstrating is only that DA is (or could be) an important element for defining the capacitor losses. This is why I consider the statement "DA induces linear distortions", if not flat wrong, at least totally misleading. Funny enough, following the same logic, one could state "any coil is inducing linear distortions", because there's always a series resistence, which can be modelled as a distributed network, which can be transposed, etc...
My work addresses the physical origins of DA. It's a large signal model that predicts the current flow in a DA material, as a result of a step voltage across. The result is presented in a parametrized form, where the parameter is material dependent, namely proportional to the molecular dipole polar momentum. For most materials, the polar momentum can be independently determined by analyzing the chemical bonds in the dielectric molecule. Which in turn are related to the material composition, therefore a powerful method to optimize dielectric compositions, from electrometer cables (where Keithley used this work) to electret based devices.
I have found no simple correlation between DA and nonlinear distortion
Just measure a quality mylar cap for DA and then measure it for nonlinear distortion. Note the vast difference in percentage.
This significantly differs from Y5V ceramics , where the DA and the nonlinear distortion are much closer together, percentage-wise.
Just measure a quality mylar cap for DA and then measure it for nonlinear distortion. Note the vast difference in percentage.
This significantly differs from Y5V ceramics , where the DA and the nonlinear distortion are much closer together, percentage-wise.
There is something to this auto upgrade, audio upgrade, and spark plug upgrade business.
It has to do with the inventive personality, who always wants to make something new. They don't usually do well in corporate environments, such as IBM, etc. because they get bored easy and are short tempered at meetings. They are what we call basement or small business inventors. Just look at Jack Bybee, Dick Sequerra, or even me.
Jack has been a consultant for the military, to Cal Tech, to SEGA, and when he finally went into business for himself, he ran the company.
Dick Sequerra worked with Telefunken in the 1950's, for Marantz in the '60's, for himself in the '70's to the present, and he does consulting for the military as well.
And so it goes.
Those who find their interests, confusing or annoying, usually are corporate types, who don't like to rock the boat, so to speak. This is what causes the friction here.
It has to do with the inventive personality, who always wants to make something new. They don't usually do well in corporate environments, such as IBM, etc. because they get bored easy and are short tempered at meetings. They are what we call basement or small business inventors. Just look at Jack Bybee, Dick Sequerra, or even me.
Jack has been a consultant for the military, to Cal Tech, to SEGA, and when he finally went into business for himself, he ran the company.
Dick Sequerra worked with Telefunken in the 1950's, for Marantz in the '60's, for himself in the '70's to the present, and he does consulting for the military as well.
And so it goes.
Those who find their interests, confusing or annoying, usually are corporate types, who don't like to rock the boat, so to speak. This is what causes the friction here.
syn08 said:
Wow I'm impressed, my Keithley 610C is a classic It's down to 1fA after a couple of minutes warmup. Tek used these techniques in some of their probes too, Barrie Gilbert pointed out that several audiophile interconnects probably repackage this as snake oil. An interesting turning of the tables.
scott wurcer said:
I had a Keithley 616, with the low noise triax cable, in a clean room controlled environment, I was down to well under 1fA while measuring MOS devices by the quasistatic method. Was using a small Faraday cage and continuously blowing the sample with high purity dry nitrogen
Off topic, one possible source for the cable directionality myth is the phono (or other balanced to single ended cables). Some RCA phono cables are build asymetrically, with the shield connected to the ground at the preamp end (which is correct). Being RCA at both ends, the asymmetry is indicated only by an arrow on the plastic jacket, pointing towards the preamp input. From here to the point at which an idiot decides it has to do with the crystaline orietation of the copper structure was only one small step.
john curl said:
There's little I can add without entering into some fancy electrokinetics math. Essentially, most of the DA materials have polar molecules, with a certain bulk dipole concentration. Before any electric field is applied across, the polar dipoles are randomly oriented in the bulk, more for amorph materials, less for electrets. Once the electric field is applied, the dipoles start rotating to align with the electric field. The displacement current flowing through the material creates heat, further enhancing the rotation speed. Bottom line, while in a non polar material the displacement current and associated time constants are determined by the external circuit, for polar materials it's the bulk phenomena that controls the displacement current for most of the transient regime, after the step voltage is applied.
I can add even less regarding capacitors; this is one of the reasons why all caps, disregarding the dielectric, should be used well under their max voltage rating, (the more DA prone material the less voltage) to avoid non linear distortions. Otherwise, non linear distortions can be clearly measurable.
Regarding linear distortions, I hope you read me correctly above: a capacitor with lots of DA can have as much "linear distortion" as a cap with no DA but lots of (e.g.) ESR. You can't tell which is which from the linearized distributed model you mentioned. I also strongly believe that linear distortions are not an issue for audio, anyway.
Thank you, it is good that you too, know that the molecules 'dance to the music'. How much inertia do they have? Does this become a real problem at high RF? You know, inertia phase?
For those who want to know, linear distortion shows up BIG TIME with asymmetrical waveforms, but not so much with sine waves. All music is asymmetrical, over short time periods. I have technical papers to prove this.
This is a good example where the simple sine wave can't do everything.
For those who want to know, linear distortion shows up BIG TIME with asymmetrical waveforms, but not so much with sine waves. All music is asymmetrical, over short time periods. I have technical papers to prove this.
This is a good example where the simple sine wave can't do everything.
john curl said:
The time constants associated with DA are in the mS to seconds range (or even minutes for low DA materials). It is safe to assume that DA doesn't have any impact at high frequencies. There are other lossy mechanisms at HF.
Linear distortions and "asymmetrical waveforms", as you put it, doesn't hold water. Prove it.
DA & DF
For caps and audio see also:
http://web.archive.org/web/20030807122631/http://capacitors.com/picking_capacitors/pickcap.htm#intro
For caps and audio see also:
http://web.archive.org/web/20030807122631/http://capacitors.com/picking_capacitors/pickcap.htm#intro
Attachments
john curl said:
Any dielectric is slightly non-linear, the stronger the field the less linear it is, so applying high voltage you change capacitance a bit and come to more non-linear region. Also, your measurement equipment can have not ideal CMRR that may show some non-linear measurements.
syn08 said:
Its interesting that you mention grounding at the preamp end. The model from Motchenbacher & Fitchen shows that lowest noise requires the shield be connected at the transducer (cartridge), something almost impossible to do in practice. Grounding at the source end for a phono cartridge really would be at the connector not at the transducer, with the potential of adding hum to the signal. if the shield is floating at the preamp end. I'm sure there are a multitude of reasons why it should be done one way or the other, all compromises of some sort.
I'm more interested in which dielectric Keithley wound up using on the triax cable, and if the driven shield reduced the sensitivity to DA.
syn08 said:
I had read that biasing a non-linear cap (electrolytic) and applying the audio across the biased cap would produce less distortion. Is that case limited to electrolytic caps? I would guess from your description that biasing the polar material and applying a small AC potential would produce less reaction from the dielectric, but the reality may not match my limited understanding. I may test this later myself.
But I've seen a few references about, floating around the net.
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