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RE: K40y-9 capacitors - highest possible voltage rating for best sound?

Posted by Michael Samra on April 3, 2017 at 22:34:16:
I have found that the 1kv rated K40Y-9 caps sound a little better than the 400v ones,provided you have a higher B+ across the cap.When I cut open a .1uf at 1000v k40Y cap,I could see oil oozing out of it. When I opened a .1uf at 400v K40Y,I didn't see oil coming out.This doesn't mean there isn't oil in in the lower voltage caps,it just means they probably use more oil in the larger caps.
I would leave your preamp alone if it sounds good but you could try the .22uf at 400v K40Y cap or maybe try a pair FT2 .1uf Russian teflons in parallel.Measure the DC voltage across the cap you have in there now. If it a 100vdc or less,leave it be.If it's 180vdc,put in a 400v cap. Now if you try the FT2 teflons,those are rated at 200v but they don't show any leakage at all until they get 780vdc across them and even then,it is very little.