That Elliot article is very good.
For some other odd opinions about caps (not endorsing I hasten to point out), I was told via an intermediary that Audio Note believe (or believed) that the crucial differences among caps for audio coupling etc. were the amounts of piezoelectric activity, and this drove their adoption (and fabrication) of paper-foil-oil caps. They helpfully made these available for purchase
. My friend wanted to use them in various places in an active crossover I designed, a hybrid tube-transistor affair. The larger ones were about the size of a quarter stick of dynamite, and of course had an irreducible loop area that proved problematic in proximity to the toroidal mains transformer's leadouts.But the worst thing for me was the leakage current, which was substantial. I quipped that they were the first capacitors I'd encountered which nearly necessitated a d.c. servo
According to Thorsten Loesch, who I gather is still quiet after a fit of pique when admonished, Qvortrup and company have returned to using film capacitors, based on what new revelations I have no idea.
Well, I think it does. For one thing it is probably provable that most of the reference LP's that folks go to have terrible low frequency group delay artifacts. Except for dynamic range and noise I don't find the low end anymore "believable" on Sheffield Labs, etc. than those 60yr. old recordings.
That's an unfair generalization, the old close minded engineer made of straw. Linear distortion and "sounds" non-linear are inexact, fuzzy, and useless to an engineer IMHO.
Again tired old characterizations. Test equpment measurements are fine, I'd love to see someone extract "what really matters" from all the garbage with a Cary or Wavac in the signal chain, let alone sampling the sound field from just about any real loudspeaker.
Considering there also are many folks and recording professionals who don't hear something, please forgive me if I want to see some published results from some controlled listening tests rather than the proverbial "everyone in the room".
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It can't be much less than 8 poles - look at how fast it falls with frequency. Unless, of course, it is heading into a zero which is just off the edge of the graph. That would create problems of its own.RNMarsh said:
Only if there is still an input signal to beat with or there are effectively two or more resonators. Otherwise ringing would show as an exponential decay (i.e. linear on a dB scale) at the resonance frequency.RNMarsh said:
If you arent into making high quality caps, like Audio Note isnt, they would know about the fields between the plates can cause plate attraction/repulsion if not using a solid dielectric. You can hear some caps vibration with signal currents passed thru them... High speed winding methods makes things worse by trapping air between layers... making for loose plate and more possibility of arcing over and break down (a reliability issue for the mfr). Only slow, tight winding can reduce this but that limits thru put and so cost is higher.
Another method to increase voltage rating reliability and prevent capacitance modulation (measured it and published it) under pulse power or high current apps is to anneal the cap.... You have all seen a flattened or oval film cap.... this is what is being done.... the cap film is heated to the plastic state and pressed... fusing the film into a solid block. no air, no moving/vibrating plates. Most caps if you saw them in half will shred but a cap made slowly and annealed will cut like a solid peice of metal. Not that that has anything to do with sound. The monolythic style caps that are not wound (WIMA) will not have these issues but they generally cant be used well in high current apps. Each has it place in apps. -RNM
Another method to increase voltage rating reliability and prevent capacitance modulation (measured it and published it) under pulse power or high current apps is to anneal the cap.... You have all seen a flattened or oval film cap.... this is what is being done.... the cap film is heated to the plastic state and pressed... fusing the film into a solid block. no air, no moving/vibrating plates. Most caps if you saw them in half will shred but a cap made slowly and annealed will cut like a solid peice of metal. Not that that has anything to do with sound. The monolythic style caps that are not wound (WIMA) will not have these issues but they generally cant be used well in high current apps. Each has it place in apps. -RNM
Thank you. I understand. Let me put it another way. A square wave with ringing on it or this water fall plot? Which better correlates to the description of loss of details in the region of the rolloff (resonance)? I think this is a better fit. thats all. Sorry i dont rememebr the details of the filter --- I thought it was a speaker cross-over but now that you mention it, it might have been an active, variable Kron-Hite filter. Anyway, my point was which better correlated.
As to some of the really big probems that are not and needs to be addressed, I havent the answeres for anyone.
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"High definition." What that has to do with the alleged sound of capacitors or the design of analog electronics is beyond me.
From the Elliot article:
From Cyril Bateman:
Here's the caption:
Generalizations abound in audio land; you are quit correct for that application with an IC that has high psrr etc. Digital pwr supply bypass too of course need it's HF performance - and very low Ls.
The water fall plot is probably a better way of showing energy storage, as square wave ringing can be caused by several different things. My problem is that in order to exhibit the phenomenon you chose an unlikely filter for an audio system. It is fairly easy to find 'scary' plots; audio salesmen use them all the time to frighten people into believing they have a problem which the gizmo being sold will fix.RNMarsh said:
So the story seems to be that high value ceramics are fine for HF bypassing but don't use one to set the LF rolloff for your system. That is, make sure if you use them that there is no appreciable signal voltage across them (and that they are not piezoelectric). You didn't actually say but that was the point you were making?serengetiplains said:
Expnad on this a bit - in your mind
Come on - extrapolate in your mind.... Mostly, I think in terms of concepts. A lower order filter will have a faster decay but wider area of affect.... and visa versa.... right? This example should be thought in terms of what would happen with two closely spaced resonances like a low pass and a high pass such as might be found in speaker filters etc etc. If you think it might matter, then nextstep would be to find ways to minimize the issue. -Thx RNM
Come on - extrapolate in your mind.... Mostly, I think in terms of concepts. A lower order filter will have a faster decay but wider area of affect.... and visa versa.... right? This example should be thought in terms of what would happen with two closely spaced resonances like a low pass and a high pass such as might be found in speaker filters etc etc. If you think it might matter, then nextstep would be to find ways to minimize the issue. -Thx RNM
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Richard, things sure have changed! '-) I remember you and I in a heated debate in choosing which two Rel. 0.1uf polystyrene caps, on TAN, 20 years ago. You put out charts and graphs at the time, comparing your RTX (I think) vs the RT that I used in my Vendetta Research phono stage at the time. You were very persuasive, then. Now, people are telling us to use ceramic caps in the power supply. What is the world coming to?
From the Elliot article:
From Cyril Bateman:
Here's the caption:
Talk about bait and switch a bypass capacitor sees no AC signal (it's there to eliminate it). This is a classic mis-use of Bateman's results. Would anyone use X7R's to make an RIAA, please.
EDIT - Sorry if I missed the point of juxaposing the two articles. My experience has been as I just said, X7R's have easily measurable distortion when voltage appears across them so according to some are useless in any audio application.
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You may be confusing order and Q. A sufficiently smooth rolloff (e.g. Bessel) could have no storage at all so nothing to decay. A filter does not necessarily have to show resonance, although sharp ones usually will.RNMarsh said:
Nobody is telling you to do anything. Just noting that different caps have different purposes. Ceramics are not universally bad. One of my standard techniques when leading a discussion group is to say something apparently outrageous just to make people think and question their own tidy assumptions.john curl said:
Interesting, but it may be that it is the shape of the initial rolloff corner rather than the final slope which really matters. The article may mix these up. However, it does perhaps raise issues relating to the brickwall filters of digital audio.john curl said:
John:
I thought Slot's book was really interesting when I first encountered it many years ago. It has a number of observations that are still very relevant.
I may want to borrow it at some point in the future.
This is a collection of observations by some really smart people at Phillips from the 70's. It predates most of the polarization we have today about audio so its pretty free of the judgementalism high end audio is rife with now.
I thought Slot's book was really interesting when I first encountered it many years ago. It has a number of observations that are still very relevant.
I may want to borrow it at some point in the future.
This is a collection of observations by some really smart people at Phillips from the 70's. It predates most of the polarization we have today about audio so its pretty free of the judgementalism high end audio is rife with now.
Yup, get with the rest of the industry. If you guys, BY MEASURMENT, can show that off the shelf ordinary capacitors can not possibly make a power supply good enough for precision instrumentation, we are all ears.
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