kamis said:
Yes, a 20MHz resonance will play havoc with the sound. It is clear that RIAA preamps need to be built using UHF/microwave techniques, as HF techniques are not good enough.jackinnj said:
Hello
If the polystyrene capacitors were not suitable I do not think they would have been recommended by Elektor in the 'Preamp 2012 by Douglas Self'. I myself made a corrector R.I.A.A from this diagram with the use of polystyrene capacitors and the result is superb (very close to Jolida JD9).
😉
I just throw this one out for comparison -- tan theta for a host of polystyrenic, polycarbonate and a multi-layer ceramic C0G. (The glitch at 3kHz arises from my test jig.)
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KEMET Polyphenylene Sulphide (PPS) 0.1 uF Film Capacitors | Mouser Romania
you have the polyphenylene sulphide caps too...a lot of them , cheap, both though hole and smd and nobody can complain about them.There are many many types of suitable capacitors.Wima fkp, ero mkc,wima fkc, ero kp1832...even wima fkp or orange drops sprague p715 are still suitable for filters in case you need high voltage for valve preamps.They are polipropylene but they are stable enough for the job .I use them all together in parallel to match the value i need with no real problem and if i could measure stable response up to 25khz squarewave through riaa networks done with such capacitors i don't think there's any problem whatsoever.Myths are a part of our lives though.The basic need for riaa capacitor is to be stable with temperature but don't imagine it's the same with radio frequency domain.You can have big shifts with temperature and you won't be able to hear that.
WIMA
Better read Cyril Bateman discourse on capacitors:
Cyril Bateman's Capacitor Sound articles | Linear Audio NL
https://www.google.ro/url?sa=t&rct=...spx?ID=37270&usg=AOvVaw37hOPEC5lpwL-KTQmP0Jvz
you have the polyphenylene sulphide caps too...a lot of them , cheap, both though hole and smd and nobody can complain about them.There are many many types of suitable capacitors.Wima fkp, ero mkc,wima fkc, ero kp1832...even wima fkp or orange drops sprague p715 are still suitable for filters in case you need high voltage for valve preamps.They are polipropylene but they are stable enough for the job .I use them all together in parallel to match the value i need with no real problem and if i could measure stable response up to 25khz squarewave through riaa networks done with such capacitors i don't think there's any problem whatsoever.Myths are a part of our lives though.The basic need for riaa capacitor is to be stable with temperature but don't imagine it's the same with radio frequency domain.You can have big shifts with temperature and you won't be able to hear that.
WIMA
Better read Cyril Bateman discourse on capacitors:
Cyril Bateman's Capacitor Sound articles | Linear Audio NL
https://www.google.ro/url?sa=t&rct=...spx?ID=37270&usg=AOvVaw37hOPEC5lpwL-KTQmP0Jvz
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Thanks RajkoM, I just asked about the capacitors in RIAA circuit, because I noticed a slight sibilance on female voices. I'm using now Philips polypropylene 1% caps. The sibilance was reduced with russian NOS silvered mica in place. I ordered the LCR caps from farnell and I will do a test.
I know, slight sibilance I've always noticed (less or more) with polypropylene capacitors. Personally, I do not like them.
Extended foil polystyrene or teflon capacitors is my choice.
Extended foil polystyrene or teflon capacitors is my choice.
The sibilants are actually part of the real content of musical program most of the time.Parametric eq's work great in reducing them when needed.If you make a fixed filter for those sibilants be sure that on other programs will change the original sound of the album.People often forget about eq-ing in search for pure sound butt that the sound itself comes from a mixer with lots of eq processing.Cartridge loading sometimes solves a great deal of it , right from the start but nothing is more correct than eq-ing.
Techniques For Vocal De-essing |
otherwise silver-mica capacitors are indeed good .
Techniques For Vocal De-essing |
otherwise silver-mica capacitors are indeed good .
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Polypropylene is not necessarily producing any sibilants, it's just passing the sound unaltered and if there's any sibillant there...Foil polypropilene cut some sibilants :
https://www.vishay.com/docs/26016/kp1830.pdf
I have some of these and they do this job:
6x ERO KP 1832 Kondensator, 9.5 nF / 1200 VDC, High End Tone Capacitor, NOS | eBay
most probably because there's less piezo effect in foil capacitors with thicker (high voltage versions) dielectric.This is just another theory i am not sure of ...it might be true though.At the same time thick dielectric capacitors(high voltage) have great losses on weak signals and can alter the high frequency content which usally lead to some sibilants through feeding oscillations. You can kill the sibillants right from the start by severely loading the cartridge and see if the polipropilene is still creating any sibillant.
https://www.vishay.com/docs/26016/kp1830.pdf
I have some of these and they do this job:
6x ERO KP 1832 Kondensator, 9.5 nF / 1200 VDC, High End Tone Capacitor, NOS | eBay
most probably because there's less piezo effect in foil capacitors with thicker (high voltage versions) dielectric.This is just another theory i am not sure of ...it might be true though.At the same time thick dielectric capacitors(high voltage) have great losses on weak signals and can alter the high frequency content which usally lead to some sibilants through feeding oscillations. You can kill the sibillants right from the start by severely loading the cartridge and see if the polipropilene is still creating any sibillant.
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Is the frequency scale on the chart in post #23 correct? Those resonant dips in sub kHz region seems implausable.
Hello everyone
Here is my corrector R.I.A.A (Douglas Self) drawn with polystyrene capacitors (1% and 2%) and you will notice that there is no ground plane. The final assembly is mounted in a box with the power and the result is really excellent, no breath or noise and the sound is really superb.
😉
Here is my corrector R.I.A.A (Douglas Self) drawn with polystyrene capacitors (1% and 2%) and you will notice that there is no ground plane. The final assembly is mounted in a box with the power and the result is really excellent, no breath or noise and the sound is really superb.
😉
Attachments
When you need higher voltage capacitors i'd say that Sprague orange drops(the cylindrical ones, not the vishay flat version) is really good for both coupling and riaa section.I used to play around with cloning guitar head-amps 10 years ago and i found that the most sought head amplifiers usually used the Sprague orange drops capacitors for all tasks: eq, decoupling and coupling .The other natural choice was silver mica for lower values .
Orange Drops: Busting Tone Control Capacitor Myths!
"People like Orange Drop capacitors because of the placebo effect. Actually, there’s a technical reason for choosing Orange Drop capacitors. Sprague was a leading name in capacitors, and in the mid-20th century produced capacitors for industry, the military, and aerospace. The Orange Drop capacitor line introduced in the 60s heralded the capacitors of the modern era—with stability, resistance to temperature variation, low moisture absorption, excellent characteristics in AC circuits, no microphonics, and other desirable attributes. (The technology can also handle high voltages, making them well-suited to tube amps.) Cornell Dubilier (CDE), another high-quality capacitor manufacturer, acquired the Orange Drop line from Sprague in late 2012."
Orange Drops: Busting Tone Control Capacitor Myths!
"People like Orange Drop capacitors because of the placebo effect. Actually, there’s a technical reason for choosing Orange Drop capacitors. Sprague was a leading name in capacitors, and in the mid-20th century produced capacitors for industry, the military, and aerospace. The Orange Drop capacitor line introduced in the 60s heralded the capacitors of the modern era—with stability, resistance to temperature variation, low moisture absorption, excellent characteristics in AC circuits, no microphonics, and other desirable attributes. (The technology can also handle high voltages, making them well-suited to tube amps.) Cornell Dubilier (CDE), another high-quality capacitor manufacturer, acquired the Orange Drop line from Sprague in late 2012."
Thanks for the info, I found some Orange drops at hificollective. I will definitely try them.
I have some polystyrene caps salvaged from an early solid state organ.
I am guessing early 1960's making them easily 50 yrs old.
What can I expect from them at that age? Will they still be usable?
Btw, while a bit off topic, I saw an interesting implementation of coupling capacitors from Ben Duncan in an "HiFi News Record Review" diy pre-amp from the mid '80's.......1984 I think. He liked VERY low frequency high pass sections and they required large value caps. At one point he proposed a composite capacitor made up of two polarized (NOT bi-polar) electrolytics mounted back to back appropriately to generate a single bipolar cap. But he advocated a high WV of 350v I think.........suggesting that this caused less distortion.
This was for an pre' amp running at very most -/+24 psu.....I recall.
Cheers Jonathan
I am guessing early 1960's making them easily 50 yrs old.
What can I expect from them at that age? Will they still be usable?
Btw, while a bit off topic, I saw an interesting implementation of coupling capacitors from Ben Duncan in an "HiFi News Record Review" diy pre-amp from the mid '80's.......1984 I think. He liked VERY low frequency high pass sections and they required large value caps. At one point he proposed a composite capacitor made up of two polarized (NOT bi-polar) electrolytics mounted back to back appropriately to generate a single bipolar cap. But he advocated a high WV of 350v I think.........suggesting that this caused less distortion.
This was for an pre' amp running at very most -/+24 psu.....I recall.
Cheers Jonathan
The capacitor values usually found in riaa filters are usually very low , much lower than the available values for electrolitic capacitors.0.1uf /50v is the lowest value i have ever seen and 500nf capacitors are used only in very low impedance filters which are rarely used.I used a maximum value of 600nf in a passive filter but couldn't find 0.1uf at around 200v as i needed.Besides...the electrolitics are loosing their values with time which isn't beneficial with filters.
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