Good to see you posting over here again... and an interesting post on PPS capacitors. You inspired me to go back and look up the Jung and Marsh Picking Capacitor series that I referenced above. Fun to see that seminal article again and remember how it turned the audio world upside-down 32 years ago!
Your dielectric constant comment got me to start a little research on PPS capacitors... I downloaded papers from AVX, Vishay, Kemet, Dearborn Electonics, CDE, and Toray (basically the first few when I googled "PPS film DF") and have done a quick scan of the AVX paper. In their table III, they compare the DA of several capacitor materials and list PPS with a DA of 0.02-0.05, which compares well to the <0.1 values cited for polyprop/polystyrene/teflon capacitors in table III of Picking Capacitors Part II. This suggests that the dialectric constant may not be the only determining factor here.
I also have seen little published information on comparisons of PPS capacitors to polyprops. There is one here:http://mysite.verizon.net/vze4c5pt/id11.html
Then I have been watching for their use in gear that I respect and found they are used or likely used in the following:
- EUVL's ES9022 DAC module, current version (from DIYAudio)
- Chaki's SD Card Player (as an optional add-on, also from DIYAudio)
- K&K RAKK DAC (based on examination of a number of photos of the board)
- Ayres QB9 (based on examination of a couple of photos of the board)
I agree that I wish Hypex had done some custom polyprops for this position... especially after changing out all three output filter caps in my NC400 to Ric Schultz-styled nuded/outer-film-oriented/stacked Wima polyprops... changing one was a nice upgrade, changing three (after about 3-4 weeks of break-in) was a much stronger improvement and I highly recommend it to anyone wanting to get away from the 'wowee-zowee' sound of the stock modules and gain a good bit of naturalness and increased delicacy without losing the dynamic punch and low-level clarity of the NCore.
I know you have some questions about whether this mod increases the module's perpensity to pick up RF... I can say that the increased clarity, cleanliness, and inter-transient silence I hear after doing the mod suggests it does not.
Julf, you seem to have a habit of taking over threads to push your own ideas and bias in audio systems and components instead of responding to or allowing others to freely respond to the questions asked. For example, earlier in this thread, you write:
"The OP asked for responses to the idea of the capacitor modification. He did not state that evidence-based responses were excluded. If an open and balanced discussion bothers you, you should probably ignore this thread."
What the OP actually asked was:
"Has anyone tried the Ric Shultz WIMA capacitor modification, (replacing a single stock wima cap .68mf with two .33mf polypropylene)"
He clearly DID NOT ask for "responses to the idea of the capacitory modification", but for feedback from those who have done this mod.
I did so, privately.
We are very clear you do not believe in this view of audio or that it has anything to offer in improving sound quality. Also that you believe that anyone who does believe so is deluded and not able to discern the truth. We get that. Please do not introject your views and bias into threads that clearly do not ask for them and are not served by them.
This is all I will say on this.
Greg in Mississippi (flame suit on!)