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Old 23rd May 2007, 03:53 PM   #21
Hartono is offline Hartono  Indonesia
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Hi Jcx,

"What exactly do you think needs Correction in Linear audio coupling applications?"

Maybe you misunderstood my sentence, my point is: it would be nice to be able to remove capacitor(any component/circuit in fact) distortion/nonlinearity , perhaps compensating it somehow, but too bad that for caps in coupling application, there's not much we can do about it. and it's too bad that while Bob can reduce capacitor error in his application, we can not do much other than changing capacitor type.

"unless you have some new data showing ppM frequency response variations are audible,"

I never mentioned that miniscule frequency response is audible in this thread. Anything can sound different and not because of frequency response



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Hartono
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Old 23rd May 2007, 03:55 PM   #22
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... we should start with the glossary: http://www.diyaudio.com/wiki/index.p...Audio+Glossary ... no entries for capacitors at all or the associated terminology ...

A simple "door opening" entry would work ... or a reference to the hydraulic model related to a capacitor ...
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Old 23rd May 2007, 04:03 PM   #23
rdf is offline rdf  Canada
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I don't think anyone suggested potential sonic differences between caps are due to frequency response aberrations. Too easy to measure.
Re: the term 'ground' was just useful shorthand to describe the common practice of putting a very low AC impedance - the capacitor - across the error voltage being measured. Every test I recall seeing placed a resistor in series with the cap, tied the other cap end to ground and drove the resistor end with the generator, measuring mid-point. Potential spuria generated by the cap are shorted by the cap. A good representative test for some applications like PS filtering but of limited value for coupling.
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Old 23rd May 2007, 05:03 PM   #24
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" ... Every test I recall seeing placed a resistor in series with the cap, tied the other cap end to ground and drove the resistor end with the generator, measuring mid-point. Potential spuria generated by the cap are shorted by the cap. ..."

... because that's where the electrons are? ... at the ground connection (usually at a more negative voltage).

I would bet there are differences in reactance of a capacitor when the resistor is in series with the cap through the ground connection, thus offering a "longer", more resistive pathway for electron flow ... No?
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Old 24th May 2007, 01:00 AM   #25
rdf is offline rdf  Canada
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The tests I referred to were similar to your setup #2 and measured across the cap. I was thinking more in term of the below, measured across the resistor. Any capacitor aberrations which manifest themselves as a current will be much easier to measure across a load resistor than across the cap due to the latter's low impedance. Conrad's test in effect was measuring voltage differences to ground caused by cap current flowing through the load resistors.
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Old 24th May 2007, 04:09 AM   #26
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And of course it's a very interesting question what happens when you reduce those resistors and increase the current level. I still question the value of the test, because of what I mentioned above. With increasing current, D becomes a factor, and the circuit is no longer balanced. I can add a resistor to balance it, but only at one frequency. Yet, I was under the impression that D had been sort of ruled out as the "x-factor" for why caps supposedly sound different. Still, it means ESR varies with frequency, and that doesn't seem completely benign. Some say it's dielectric absorption, but others say not. That's actually easier to test (I think) by building up a physical version of the DA model, and making DA really horrible, then seeing if it sounds different. Not enough hours in a day- right now I'm rebuilding an amp and working on my oscillation overthruster, er, sniffer.
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Old 24th May 2007, 04:26 PM   #27
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Default This Capacitor type Comparison thread

rdf: " ... I was thinking more in terms of the [attached diagram above], measured across the resistor. Any capacitor aberrations which manifest themselves as a current will be much easier to measure across a load resistor than across the cap due to the latter's low impedance. ..."

mmm .. looks suspiciously like many amplifier inputs = the resistor representing the "load" or input impedence of the amp and the cap blocking any DC offset.

Typical resistor/load values might be from 10K to 250K Ohms. (Wirewound = no? Metal film = ? Other type = ? ...)

The capacitor of course must be good enough to pass through any and all audio information in with relatively flat response ( ~20 to ~20K Htz ? ... 5 to 50K Htz? ... 5 to 200K Htz.?). Hopefully the cap will be good enough to not interfer, distort or otherwise change the audio by its presence. (It is axiomatic for "golden ear" designs to eliminate these caps entirely from the signal path, where possible.)

Thus the whole point of this discussion and thread is to discover the optimum capacitor type for audio application. ... And possibly to include the latest "wise old men" theories and experience regarding selection of capacitors and associated components into a Wiki think piece ... this being, in my opinion, a critical piece of amplifier design and construction knowledge.

Consider, as many of you already know, the use of decent passive components at the imput can make a world of difference at the output ... an extra US$0.50 spent at the input can easily be worth more than US$5.00 spent on corrections at the output. ...

a chart:
Capacitor Type ... Material type and quality ... approximate costs ... Best usage ... ???
================================================== ==========
Ceramic 200 volt ... inexpensive, radial leads ... $0.05 ... high frequency bypass (non audio?) ... etc. ...

Comment? Contributions? ...
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Old 24th May 2007, 04:39 PM   #28
Hartono is offline Hartono  Indonesia
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"optimum capacitor type"

I thought we already agree on this
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Old 24th May 2007, 04:44 PM   #29
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Fast Eddy posted:

... because that's where the electrons are? ... at the ground connection (usually at a more negative voltage).

I would bet there are differences in reactance of a capacitor when the resistor is in series with the cap through the ground connection, thus offering a "longer", more resistive pathway for electron flow ... No?



I am not sure whether this is in jest or not

If not, you have a rather bizarre understanding of electrical current, IMO
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Old 24th May 2007, 04:47 PM   #30
Hartono is offline Hartono  Indonesia
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"thus offering a "longer", more resistive pathway for electron flow ... No? "

at least the resistive part is correct...... it's a resistor hey !!! [Joke]
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