polypropylene capacitors

[rayma]

Can't you get a close photo of the markings?

 

[SirPaulGerman]

that the best I can do, it came from my tech, he is convinced is Polypropylene becasue of the color.

 

[SirPaulGerman]

got another one

 

[rayma]

Appears to be Panasonic ECQ-V series metallized polyester film.
Also replace those ceramic disc caps with COG/NPO types.

 

[NanoFarad]

I can see a 5pf NPO/COG there with black paint on top. That 221K ceramic isn't COG, that's for sure.

 

[SirPaulGerman]

are the bigger one in the 1st picture also Panasonic?

 

[rayma]

No way to tell, they're just dipped film.

 

[SirPaulGerman]

The preamp is from 1990
Should I change those ?
He already did some changes

 

[mchambin]

So, there is nothing new since the original post.
Film capacitors in 10uF, 20uF, 33uF in small volume, low voltage are expensive.
However an information, I liked going through all posts is about capacitor matching.

One can expect 0.5% matching in 10% film capacitors.
Any more information ? About 10uF, 20uF, 33uF, small capacitors, good for 48 volt phantom isolation ?

 

[dotneck335]

"One can expect 0.5% matching in 10% film capacitors."
Is that a verifiable FACT? Have you had such experience?

 

[wrenchone]

If it's a no-name cap I would strongly suspect metallized polyester as default choice, just because they're cheaper to make. There are probably a lot of polyester caps out there being sold as polypropylene.

 

[rayma]

One can expect 0.5% matching in 10% film capacitors.

It may be possible in a given batch, although the absolute value will tend toward the smaller limit more than that, due to cost savings.

 

[wrenchone]

Panasonic has a line of 450V rated polypropylene caps that are extremely compact, used as "bus caps" for PFC applications - the "bus cap" is the cap immediately following the rectifier bridge in a PFC, used as a charge reservoir.

 

[SirPaulGerman]

I told my tech to replace the ones in the signal path and the ceramics, I think is a good compromise.

There are few NOS electrocube poly-carbonate capacitors out there, are those any good for home audio ?

 

[dotneck335]

"Panasonic has a line of 450V rated polypropylene caps that are extremely compact, used as "bus caps" for PFC applications."
Got a part #?

 

[rayma]

There are few NOS electrocube poly-carbonate capacitors out there, are those any good for home audio ?

PP will be fine. It's best if they fit the board properly.

 

[mchambin]

"One can expect 0.5% matching in 10% film capacitors."
Is that a verifiable FACT? Have you had such experience?

I would like to know if that is true.
And know more about what has been found when matching capacitors.
Typically for 48v phantom power isolation in microphone preamplifiers.

 

[mchambin]

Panasonic has a line of 450V rated polypropylene caps that are extremely compact, used as "bus caps" for PFC applications - the "bus cap" is the cap immediately following the rectifier bridge in a PFC, used as a charge reservoir.

Interesting, what size ?

 

[wrenchone]

Here's a link to a 1uF cap at Digi-Key. I've been getting the 2u2 size - still pretty compact for a 450V cap
https://www.digikey.com/en/products/detail/panasonic-electronic-components/ECW-FD2W105J4/3844565

 

[wrenchone]

Here's the link to the 2.2uF, 450V cap. It fits in bout the same outline as the Roederstein 2.2uF, 63V polycarbonates I've been using for the "Nakamichi" unity gain DC feedback scheme that I use in just about every amp I've designed since the late 70's.

https://www.digikey.com/en/products/detail/panasonic-electronic-components/ECW-FD2W225J/3844558