[quote author="GregL"]I'm new here but have about 25 years experience experimenting with
capacitor types in all different types of gear. Whether polypro or oil caps are better really will depend on the circuit and where they are used in the circuit. Oil caps can sound very good in circuits that are running open loop, especially if the preamp/amp in question is part of a system where there may be strident sounding components like some horn speakers.
Or if you want a mic preamp with a very vintage, smooth tonality.Oil caps also work great in power supplies for vacuum tube equipment. But in a lot of gear, using them as coupling caps will blunt the sound unacceptably.
The red WIMA metallized polypro's seem to work well about anywhere and I have yet to have a reliability issue with any of them. Lots of hi end recording and stereo gear use these. Other metallized polypro's I'm not so sure about (although again I have put many Solen's into gear and not ever had an issue, and they sound pretty good in a lot of instances).
The Sprague orange drop polypro film and foil in my experience work very well. Nice, clear, not too strident. Some people will quibble with this but I think they are good caps. And they are inexpensive. Do not get these mixed up with the Orange drop polyester or metallized polypro!
If you really want to up the ante some of the audiophile caps like Hovland and Auricap, MIT etc. can be great but are very expensive and in many places may not make that much of a difference. I really like the Hovlands but it may depend on your circuit and implementation (and subjective taste). These are all polypro by the way.
Replacing picofard valure caps-if you need to use ceramics COG's have types have the best DA charactersitics. Using better caps where these are used may not seem like it would make a big difference but I have had instances where replacing all ceramic caps with COG's (especially op amp stuff) has made a big difference on the top end smoothness. Better yet,
use good quality polystyrenes if you can find them.
Teflon is great but if you can afford to build anything with these you can afford to buy whatever gear you want!
I could go into electrolytics but I gotta get back to work.
Greg[/quote]
Welcome as well Greg.
I agree about the C0G parts---Jung and Marsh oddly seem to lump all ceramics together and the NP0/C0G's are very decent low-loss parts. They are just bulky for anything very large, although if you pay enough they can get up to 100nF with reasonable size. AVX made a power supply cap of 100's of microfarads with C0G material, for the International Space Station, but it probably cost the gov't $100k or more.
The paper/oil caps are exceptionally low in microphonics/piezoelectric effects. Supposedly that's why Peter Qvortrup likes them (Audio Note). They are not low dielectric absorption or even very low d.c. leakage. When I did a high-end piece for a friend, who insisted on using them as output coupling caps, I quipped that they were the first non-electrolytic caps that required a d.c. servo.
Lately I've had to do a lot of design with SMD and the capacitors are usually ceramic X7R and are terrible. It amazes me that the stuff doesn't sound worse.
