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 Post subject: Origins of Audio obsessions with capacitors
PostPosted: Feb Sun 03, 2019 5:41 pm 
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These two articles in Audio might be the origin of the obsession with capacitors and their influence on hi-fi gear in the American media. I had these cut out in a notebook at one time but the notebook got ruined. So this website has the two part article in Audio Magazine. It is by Jung, How to Pick Capacitors for Audio in the Feb and March 1980 issues at this link https://www.americanradiohistory.com/Audio-Magazine.htm Has actual tests of the different caps as well as the descriptives of their impact on sound.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Sun 03, 2019 6:25 pm 
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I skimmed through the articles since I already knew about this phenomenon having read about it in several books on amplifier design. The authors definitely were not in the snake oil selling business; they were doing actual tests to determine the distortion caused by capacitors in audio circuits. The key takeaway is that certain dielectrics have significant nonlinearity which manifests as harmonic distortion when there is an AC voltage across the capacitor such as those used in filters or EQ networks, not so much as coupling capacitors. This kind of article does not explain certain 'phool or vintage gear crowd obsessions with things like paper/oil capacitors, special foil materials, or special construction techniques. The article was concerned with standard, off-the-shelf, brand name capacitors.


Capacitor distortion is a real and measurable thing, but most of the time the distortion levels are pretty low, but if trying to design for lowest distortion or doing precision analog design (like the analog front end for a precision ADC or measurement system) it does need to be taken into account. This does not call for the need to use expensive boutique "audiophile" parts; just good quality stuff from reputable manufacturers.


Places in audio where capacitor distortion can be a problem are: RIAA phono stages, tone controls or equalizers, filters, and speaker crossover networks. These circuits use capacitors in ways that there will be significant AC voltages across them in normal operation.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Sun 03, 2019 6:33 pm 
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Many many years ago when I designed A/D converters and Sample and Hold circuits, glass or polystyrene were the goto types, low dielectric absorption if I remember right.

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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Sun 03, 2019 7:16 pm 
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I know that the industry for higher cost gear got away from using ceramic and polyester caps for coupling. I had a pretty high end preamp from the mid 70s and it used alot of those. But they could never get fully away from electrolytics, so now you have varieties of "special" electrolytics for audio circuits. Amongst other things some specs better than run of the mill types. Might be beneficial or not. With this article in mind I refurbished a PAS-3 preamp in the mid 80s using PP caps from work and RN60 metal film caps for lower noise. It sounded nice. Audio mag. had alot of exellent and educational articles about hi fi hardware. And even construction projects for the lastest concepts in amp design and etc. They did not get as far out on a limb as the more esoteric hi fi mags that still exist. Greatly missed. Equipment reviews better than High Fidelity and technical measurements good.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Sun 03, 2019 8:56 pm 
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Another form of MOB MENTALITY.

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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Mon 04, 2019 2:14 am 
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Maybe these audiophile-grade caps have better test results, but not enough that the human ear could tell the difference.

Of course, after someone spends $20 on one capacitor, they are inclined to believe they hear a difference :wink:

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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Mon 04, 2019 2:56 am 
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I can see switching to better caps but the gold plated hand would by monks in special rice paper jobs are probably a little overkill. They took some valid research and ran with it over the edge to make money. You can get decent quality polypropylene caps for alot less than the anointed specialties. Actually not much more than old fashioned polyester jobs.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Tue 05, 2019 1:09 am 
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Walt Jung is one of the most highly regarded analog circuit engineers around. He pretty much defined the low noise, low distortion op amp during his career at Linear Technology and Analog Devices. Indeed, his work on distortion resulting from different types of capacitors and other passive components sprang from the development of low distortion op amps.

The simple truth of the matter is, all real world components are capable of exhibiting non-linear behavior (meaning they will cause distortion) under certain conditions. Good circuit designers know this and avoid troublesome circuits and components, or control the distortion by other means. But they do it with real measurements and calculations, not with their imaginations.

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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Tue 05, 2019 1:55 am 
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Chris108 wrote:
Walt Jung is one of the most highly regarded analog circuit engineers around. He pretty much defined the low noise, low distortion op amp during his career at Linear Technology and Analog Devices. Indeed, his work on distortion resulting from different types of capacitors and other passive components sprang from the development of low distortion op amps.

The simple truth of the matter is, all real world components are capable of exhibiting non-linear behavior (meaning they will cause distortion) under certain conditions. Good circuit designers know this and avoid troublesome circuits and components, or control the distortion by other means. But they do it with real measurements and calculations, not with their imaginations.


Exactly. I'm not sure how a well designed test and well written article investigating distortion caused by capacitors and dedicated to advancing the state of the art in audio translates to the world of expen$ive foofoo "audio grade" capacitors. Has anyone done similar tests on the 'phool parts to see how they perform? None that I know of, it's all "I know what I hear" nonsense. If the 'phools took the advice of this article they would use polystyrene and polypropylene capacitors in their designs instead of mostly obsolete stuff like paper in oil capacitors and other parts with a good marketing story behind them and not much else, and save lots of money by doing so.

As far as the distortion being below the level of audibility, that's likely so, but when designing for low distortion (even if it's just for spec bragging rights) why tolerate more distortion than necessary, especially if the cost isn't that much greater? At least you'd be able to say the circuit in question isn't the reason for poor sound quality.

Of course, none of this applies to our old radios since they weren't designed to be hi-fi for the most part.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Tue 05, 2019 2:40 am 
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Well regardless, Audio as I remember and see is full of useful information about stuff like acoustics, speaker design, measuring amplifier distortions, building projects, and due to the time period it was out, kinda not too much into the pixie dust magical stuff. Much more than just pretty pictures and reviews. But not rigidly technical to the point of disregarding all subjective impressions of stuff.


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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Wed 06, 2019 12:35 am 
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I grew up in electronics using Jung's "Op Amp Cookbook" as one of my bibles. I'd accept his test results without much question. Or more accurately, without ANY question.

I wonder what he'd have to say about low oxygen speaker cables, cryogenically treated AC outlets, and plutonium plated chassis screws. :-D And let's not forget the concrete subwoofer enclosure. :roll:

Sure sounds nice... ahhhh, that plutonium makes the audio positively glow in the dark.

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 Post subject: Re: Origins of Audio obsessions with capacitors
PostPosted: Feb Thu 07, 2019 5:01 pm 
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Quote:
Exactly. I'm not sure how a well designed test and well written article investigating distortion caused by capacitors and dedicated to advancing the state of the art in audio translates to the world of expen$ive foofoo "audio grade" capacitors. [...]


Jung himself tells you what the impetus is at the top of his article. He says outright that the fact that all electronic components exhibit non-linear behavior under the right conditions was well known. It was generally neglected in the past because tubes and early transistors produce so much distortion and noise themselves, the tiny amount of distortion caused by properly applied passive components was buried. However, with the low distortion op amps Jung was creating at the time, the distortion in passive components becomes sizable by comparison. Having designed op amps that were essentially free of distortion, but still finding it in practical circuits, he and other engineers went back and looked at the passives. It is important to note that it wasn't just capacitors that were the culprits; there are nonlinear distortions in resistors and other parts. Even the type of insulation on the wires can have an impact.

One thing people don't generally appreciate about Jung's articles is, he applied very large AC voltages to the capacitors in his tests in order to get demonstrable results. If you were a home hobbyist or a small company in 1980, you probably didn't have the coin for signal generators and distortion analyzers capable of measuring 0.001% THD. So he made the voltages much higher than would typically be applied in normal circuit design so engineers and experimenters following along with rudimentary equipment could observe results which would be orders of magnitude smaller in the real world. Unfortunately, one of the consequences was that non-technical and quasi-technical people cherry-picked the articles and turned it into a "my capacitor sounds better than your capacitor" kind of thing.

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As far as the distortion being below the level of audibility, that's likely so, but when designing for low distortion (even if it's just for spec bragging rights) why tolerate more distortion than necessary, especially if the cost isn't that much greater? At least you'd be able to say the circuit in question isn't the reason for poor sound quality.


It has to be remembered that it was the rare tube amplifier that produced less than 2% or 3% THD for any length of time, and 0.1% THD was considered pretty darn good for a solid state amplifier in the '70s and '80s. When you get to 0.01% THD or below, you have to start taking things like passive non-linearity into account. Jung was trying to wake circuit engineers and designers up to the kinds of things they'd have to deal with as they got involved in lower distortion equipment. His results are just as applicable to instrumentation, analog computers, and other fields as they are to audio.

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