I'm one of the others Ian 🙂 , I bought some 100nF SMR's 6 or more years ago for bypass duty when I recapped my playmaster series 200.
The PPS are superior to polycarbonate in most respects, their main selling point is high temperature stability for automotive use.
I can't remember which but one of the pps caps manufactures datasheets lists audio as one of the applications.
Tony.
The PPS are superior to polycarbonate in most respects, their main selling point is high temperature stability for automotive use.
I can't remember which but one of the pps caps manufactures datasheets lists audio as one of the applications.
Tony.
Arrrgh! I ordered those ECQE(F) yesterday to try in place of my WIMA MKP4/Vishay MKP1839 signal path dc blocking caps and they have just arrived.
Definitely not PPS...someone at Farnell must have been sloppy at the data entry!!
Not sure whether it is worthwhile de-soldering the current MKP caps to try some "metallised polyester" film caps that aren't designed for audio.
Are they useful for anything else audio-wise?
No - That would be a backward step, WIMA MKP4 and Vishay MKP1839 are superior. Short of spending megabucks what you've already got in there are as good as you can do.
A little hint from my sandbox experience - where there is decent amount of DC across a cap I found that the "pre-stressing" of the dielectric meant that I could not pick the difference between good polypropylene and $50+ audio jewellery. Where there was NO DC across the cap, and dielectric stress was reversing with the audio signal then I could pick the difference, hysteresis at the electric field reversal I would guess. Most caps in tube audio will have enough DC across them that there will never be a reversal of the electric field (due to the audio signal) and so there is not much point in trying the audio jewellery.
I' doning my flameproof vest as I type, in anticipation - just my experience/opinion, feel free to disagree.
Cheers,
Ian
A little hint from my sandbox experience - where there is decent amount of DC across a cap I found that the "pre-stressing" of the dielectric meant that I could not pick the difference between good polypropylene and $50+ audio jewellery. Where there was NO DC across the cap, and dielectric stress was reversing with the audio signal then I could pick the difference, hysteresis at the electric field reversal I would guess. Most caps in tube audio will have enough DC across them that there will never be a reversal of the electric field (due to the audio signal) and so there is not much point in trying the audio jewellery.
I' doning my flameproof vest as I type, in anticipation - just my experience/opinion, feel free to disagree.
Cheers,
Ian
could that be why some people "hear" a difference between, say, 400v rated caps and 630v rated caps? (ie. less apparent dielectric stress?)
yeah, definitely not going to use them in place of the MKP. any ideas as to what other sections of an audio circuit the mylar might come in handy?
For those who are keen to try PPS caps at tube voltages, Newark is stocking a line of PPS X capacitors.
instead of eyeing the poor cap, why not look at the circuit itself? maybe there is room for optimization....
I think I've almost got to the point of having this circuit optimised (the coupling caps are IMHO the last frontier).
Rather than paste some info I've posted earlier (and risk being labelled a spammer!) -
Circuit is here:
http://www.diyaudio.com/forums/digi...-w-6dj8-srpp-mod-suggestions.html#post2619638
The mods I've done are here:
http://www.diyaudio.com/forums/tubes-valves/193207-pio-coupling-caps-damaged-used-3.html#post2650082
Any other suggestions obviously very welcome!
Rather than paste some info I've posted earlier (and risk being labelled a spammer!) -
Circuit is here:
http://www.diyaudio.com/forums/digi...-w-6dj8-srpp-mod-suggestions.html#post2619638
The mods I've done are here:
http://www.diyaudio.com/forums/tubes-valves/193207-pio-coupling-caps-damaged-used-3.html#post2650082
Any other suggestions obviously very welcome!
you can try the textbook common cathode-cathode follower buffer in lieu of the SRPP, you may even like it....
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