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Old 2nd February 2013, 06:30 PM   #1681
davada is offline davada  Canada
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Quote:
Originally Posted by myhrrhleine View Post
Hi all,

I was just wondering if an SVF oscillator might have lower distortion with series / parallel capacitors?

Ill try it and let you know.

Capacitor in series have a tendency to not share equal amount of charge.
I have no idea what effect this may have in a circuit like an integrator.
There has been discussion that capacitors do create distortion but I'm not clear
about the mechanism that causes this. If there is no information on cause then all we can do is study the effect.
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Old 2nd February 2013, 06:47 PM   #1682
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by davada View Post
Ill try it and let you know.

Capacitor in series have a tendency to not share equal amount of charge.
I have no idea what effect this may have in a circuit like an integrator.
There has been discussion that capacitors do create distortion but I'm not clear
about the mechanism that causes this. If there is no information on cause then all we can do is study the effect.
D.Self did a lot of work on capacitor distortion.
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Old 2nd February 2013, 07:27 PM   #1683
richiem is offline richiem  United States
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In the absence of facts, I'll opine that low ESR and low dielectric absorption are the two most important characteristics for lowest distortion. Polystyrene or polypropylene seem best suited, and my trials of various dielectric materials in my version of Bob Cordell's SVF oscillator support this opinion.

Ceramics are generally the worst; tantalums not so great; then aluminum electrolytics (haven't tried the new "solid" types); them films, with mylar OK, but the two mentioned above the best. I tried these at 100Hz and/or 1kHz, depending on available capacitance values.

Once the polypropylenes proved good, I haven't looked back -- they are my choice due to wide availability and low cost. If polystyrenes of the right values can be had, then they are first choice. You guys in the EU might have better access to styrenes than we in North America.
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Old 2nd February 2013, 07:40 PM   #1684
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Cyril Bateman demonstrated that extended foil polystyrene is best at about -135db.
But, how would one get lower?
Series or parallel or combination or other?
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Old 2nd February 2013, 08:47 PM   #1685
coluke is offline coluke  Italy
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Quote:
Originally Posted by richiem View Post
Ceramics are generally the worst;
Except for C0G/NP0 types - in my experience they're almost as good as polystyrene and polypropylene ones.

L.
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Old 2nd February 2013, 08:57 PM   #1686
davada is offline davada  Canada
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Quote:
Originally Posted by coluke View Post
Except for C0G/NP0 types - in my experience they're almost as good as polystyrene and polypropylene ones.

L.
It's only because ceramics have a bad rep.
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Old 2nd February 2013, 10:13 PM   #1687
RNMarsh is offline RNMarsh  United States
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The volume cap users have changed over to polyprop because of size and max temp rating. This has caused PS type mfr to be dropped by more and more cap companies due to low volume.... After that the PS film makers stopped producing the film. Now there is one mfr in China still making them to a high standard. REL-CAP in Calif uses their film source as it is highest quality film. But REL-CAP is a custom cap maker and does not stock caps of any type-- built to customers order. Some audiophile distibutors exist that have ordered and stock such parts from REL. The best is always hard to come by as they cost more. But if not enough useage, all will be lost. Just as happened with some super good transistors and jFETs..... no longer available. Get PS if you can and while you can... otherwise use a high quality made PP. Thx-RNMarsh
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Old 3rd February 2013, 03:04 AM   #1688
1audio is offline 1audio  United States
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This gent seems to be able to measure THD to -130+dB with a Lynx L22 in loopback : http://www.diyaudio.com/forums/analo...ml#post3352626 . I have my doubts but perhaps its possible. Does anyone else have experience with the L22? It would be a simple solution.
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Old 3rd February 2013, 04:02 AM   #1689
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
This gent seems to be able to measure THD to -130+dB with a Lynx L22 in loopback : http://www.diyaudio.com/forums/analo...ml#post3352626 . I have my doubts but perhaps its possible. Does anyone else have experience with the L22? It would be a simple solution.

Hi Demian,

What he's showing there is impossible.
This card isn't much better than the QA400.
I think he has a gross mis-calibration.
ARTA is showing a 1Vrms FS input signal.

L22 specs:

Analog In Performance(Analog performance specs measured at 44.1 kHz sample rate, 24-bit, card installed in computer)

Frequency Response
20 - 20 kHz, 0.05 dB at 44.1 kHz sample rate
Dynamic Range
117 dB, A-wtd.

Signal-to-Noise
116 dB, A-wtd.

Input THD+N
-108 dB (0.0004%) @ -1 dBFS
-104 dB (0.0006%) @ -8 dBFS
1 kHz signal, 22Hz - 22kHz BW
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Old 3rd February 2013, 04:27 AM   #1690
richiem is offline richiem  United States
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Yes, I too doubt the Lynx results. As to C0G/NP0 -- I have been told numerous times by folks I trusted that all of the ceramic cap materials are to a greater or lesser extent piezoelectric. I think this is not a Good Thing. But again, in the absence of facts....
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