Disc-ceramic capacitors for LPF use:
I have replaced a lot of HF SS amp LPF caps over time.
The best parts are not uncommon, but not terribly simple to find,
either.
There are two keys:
1. Get the physically-largest cap you can with the highest voltage
rating. Generally larger than a quarter is good.
2. Make sure it's "Type 1" dielectric.
Key #1 maximizes the current rating, which is nearly never obtainable
from the manufacturer.
Key #2, in English, means that NP0 (or C0G) caps are the ideal. The
larger the capacitance value, the less likely you can find it in NP0
(and afford it). Any tempco marking with an "N" (e.g., N750, N3300,
etc.) is still Type 1 and should be sufficient for LPF service.
You can find all sorts of kV-rated capacitors at the mainline
distributors. But most of the time, they are not Type 1. If it doesn't
have an N in the tempco (or if no tempco marking exists), play it safe
and find a different cap.
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