rsavas, would you make a quality cap with FR-4? That is the answer to your question.
And indeed, that's how the hook problem was noted. I would love to find that reference.
I think it was Tektronix who had come up with some integrated circuits for the vertical amplifier chain --- was it for the 485, or one of the mainframe 7000 series scopes? --- and used some PCB pads for low-value capacitors as part of the matching networks to the chips.
I should ask John Addis if he recalls that article, as I believe he was there at the time.
Where did you get these 30-50G resistors? Do they obey Ohm's Law? What's the application?Bingo, I needed those for a circuit with 30-50G feedback resistors, but even so the board needed to be spotless.
I'm interested in these for capacitor mikes.
Digital Absorption noise? It should sound like sucking of numbers.
Can't imagine how it sounds...
Scott showed a graph of it a few months ago- one of those, "Geez, that's obvious!" but only in retrospect.
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DA, Digital Absortion Noise, good one, okay, back to my Maxwell equation books or whatever & the net for an explanation of that one. So, if it is square wave like, it is a problem but if it is a sine wave like, we are okay 🙂 = nuts, my ears are no good for this stuff anyways. As my dad said to me, "I don't listen to the record noise, I listen to the music"
Rick
Know not at all, but I see lots of claimed "quality cap's" encapsulated in epoxy, I wonder why that is, if it is no good? What would you suggest, that the capacitor MFG's use instead of epoxy, as an encapsulant?rsavas, would you make a quality cap with FR-4? That is the answer to your question.
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DA, Digital Absortion Noise, good one, okay, back to my Maxwell equation books or whatever & the net for an explanation of that one. So, if it is square wave like, it is a problem but if it is a sine wave like, we are okay 🙂 = nuts, my ears are no good for this stuff anyways. As my dad said to me, "I don't listen to the record noise, I listen to the music"
Rick
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So why are you thinking of conductive plastics now? Horrible compromise.
If you know how to formulate and handle these materials, they can do EM tricks that metals can't.
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Know not at all, but I see lots of claimed "quality cap's" encapsulated in epoxy, I wonder why that is, if it no good? What would you suggest, that the capacitor MFG's use instead of epoxy, as an encapsulant?
It's an inapt analogy, marketing driven, not technical. Would you make a resistor out of Teflon? A circuit board out of zinc?
Where did you get these 30-50G resistors? Do they obey Ohm's Law? What's the application?
I'm interested in these for capacitor mikes.
"Founded in 1969, the company’s initial products were specialized miniature chip resistors - from 1 megohm to over 1 teraohm. Still offered commercially today, these resistors are characterized by low noise and low capacitance, making them especially suitable as feedback resistors in hybrid transimpedance amplifiers (the resistors have been used to a reported 4.2 Kelvin cryogenic temperature)."
(from the Eltec Instruments website)
I used to screen the 1Tohm parts for actual resistance and excess noise at 77K. I recall one that behaved as if it had about three different paths for the current. Needless to say it was rejected.
If you know how to formulate and handle these materials, they can do EM tricks that metals can't.
Would you kindly teach us? Any measurements to support your claim?
Sure would, if I could find a sucker to buy them and only for that reason alone!! Not really, I am not like that!! I'd tell him the truth, to be honest. I hate people taking advantage of others.Would you make a resistor out of Teflon? A circuit board out of zinc?
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Where did you get these 30-50G resistors? Do they obey Ohm's Law? What's the application?
I'm interested in these for capacitor mikes.
they were special order from one of the resistor companies, glass encapsulated, silicone coating to make them hydophobic on the outside, the tempco wasnt great. They were used for a flame ionization detector that counts carbon atoms going through a flame.
Wrinkle
Would you kindly teach us? Any measurements to support your claim?
I can't go into formulation, that would (as has) taken many books to fill, but the main points are that you can easily make a panel (or enclosure) that has a conductivity gradient chosen to maximize EM absorption. Likewise, you can make a material with a very high loss factor or one with novel magnetic properties. The literature is full of measurements, my own were done back in the '80s; some of my patents from Lockheed should give you more than a hint.
These days, I don't design equipment that needs heroic measures to function properly.
they were special order from one of the resistor companies, glass encapsulated, silicone coating to make them hydophobic on the outside, the tempco wasnt great. They were used for a flame ionization detector that counts carbon atoms going through a flame.
Wrinkle
A Victoreen "HI-MEG" on teflon feedthroughs, 2000 megohms in this case. I actually needed it for a measurement of JFET gate leakage recently.
Attachments
And indeed, that's how the hook problem was noted. I would love to find that reference.
I think it was Tektronix who had come up with some integrated circuits for the vertical amplifier chain --- was it for the 485, or one of the mainframe 7000 series scopes? --- and used some PCB pads for low-value capacitors as part of the matching networks to the chips.
I should ask John Addis if he recalls that article, as I believe he was there at the time.
Long before that trimmers were made of thin enamel insulated wires wound around thicker wires. I saw that in Soviet radio receivers designed in 1950'th.
The 'best' caps generally do not use epoxy as an outside coating. AND they certainly don't use epoxy for the cap dielectric material. However, a circuit board is a number of small caps that are created by the board material and the spacing between conductors. That is why SY recommends Teflon standoffs, when he considers them necessary (I do too). Taking things to the ultimate, Teflon boards are 'better' than FR-4 boards, just like carbon fiber might be a 'better' material for a race car than steel.
Thanks Scott, for adding to my confusion -🙂 Sorry to ask, what is "DA" noise?, boy, do I have a lot to learn and their is only so much time left!! Cheers Rick
I was not totally kidding, like Tek if you make capacitors out of FR4 they have horrible dielectric absorption which acts as a loss resistance which does have noise in a high impedance circuit. I easily measured it in a mica cap which is actually supposed to be a cap. Those Tek guys probably thought they were very clever.
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Long before that trimmers were made of thin enamel insulated wires wound around thicker wires. I saw that in Soviet radio receivers designed in 1950'th.
Around here those used to be called "gimmicks".
Taking things to the ultimate, Teflon boards are 'better' than FR-4 boards, just like carbon fiber might be a 'better' material for a race car than steel.
Problem is, when it comes to actual performance for this application, it's not better. Either it's unfilled, in which case it's mechanically floppy and cold-flows easily (nice to have a flexible, rattly board in a soundfield?), or it's glass filled and the bulk dielectric properties are dominated by the glass as is the case for glass epoxy composite. In both cases, the trace integrity is markedly degraded compared to glass epoxy, reducing reliability.
Teflon PCB is a good choice for some very specialized applications, but audio isn't one of them- except for the fashion and hype factor, of course. The faith-based audiophile pays more and gets poorer performance and reliability.
edit: If you want to have your cake and eat it too, you could do point to point between standoffs (silver wire, natch!) so that the dielectrics are dominated by Teflon and air. As your Parasound demonstrates, you don't really get any performance advantage by avoiding reliable glass epoxy, but it IS a high coolness factor.
Wash your hands!A Victoreen "HI-MEG" on teflon feedthroughs, 2000 megohms in this case. I actually needed it for a measurement of JFET gate leakage recently.
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Teflon PCB is a good choice for some very specialized applications, but audio isn't one of them- except for the fashion and hype factor, of course. The faith-based audiophile pays more and gets poorer performance and reliability.
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Unless Teflon PCBs have actual audible benefits.
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