Some other forums are sending people here for information. For the time watchers, yup, old thread. Doesn't matter for the folks looking for information, and stumble upon this. I dig up old threads all the time, when I am researching.
Russian PIO caps K42Y-2
500V 0,1uf 10% tol.
10 pcs
K42Y-2 - capacitors have a unique perky disposition among the paper series of russian caps.
Different from the famous
K40Y-9 series is metallized dielectric, but this does not mean that sound are worse.
They sound a bit different. Soft tactful bass, sweet treble, cheeky mid emphasized dirty.
Recommended applications - shading frequency amplifier tembroblok sound in the style of old school. _____________________________ This is one of the Russian sellers from eBay trying to describe the cap, taken word for word. Here is another, from a seller in the USA.
Russian military K42Y-2 .047uf 250V capacitor. K42's are metalized paper in oil, glass sealed in a metal body.
These make great tone capacitors for guitars. The metalized paper gives it a brighter less unadulterated sound making it an interesting choice for strats, teles, p-basses.
Compact dimensions make these are easy to install even in tight cavities.
These caps are not unlike a new speaker and will sound there best after being broken in for several hours. From Bob Latino......
What Corndog has written here is exactly what I have noticed with the K40-Y and the K42-Y caps. There is very little (if any) difference between these two capacitors at least if used as main coupling capacitors in a tube amp. Both are slightly on the warm side and both give a very wide and deep "3D type" soundstage. If you buy them on Ebay, K40 caps tend to be a little more expensive than the K42's but that does not mean that they are "better". K42 caps also tend to be somewhat smaller in size than their K40 counterparts with the capacitance and voltage ratings being the same. This makes a K42 easier to fit into some situations that have limited space.
Bob