Today’s bookshelf isn’t a datasheet or a book. It’s actually just a webpage (which I suppose would make it an ‘EE bookmark‘), but it’s one that I like a lot, so I figured I’d share it.
Which capacitors sound better than others? Or perhaps, which ones distort the least? This is a contentious topic among audiophiles, musicians, DIY synth builders and occasionally HAMs as well. I don’t actually want to wade into this argument. My main purpose in writing this post is to share with you this excellent webpage over at greygum.net. I keep this one near the top of my bookmarks folder, and make sure it stays there when I migrate to a new computer.
This page dates from 1999, but the information is still good. It’s also a great example of an awesome late-90’s webpage.
The author, Steve, performed some tests to find the D-E curve of various types of capacitors (his test set-up is described at the bottom of the page). The results can be eye-opening.
The two worst performers on that page were electrolytics (which exhibit marked hysteresis, particularly the tantalum, above), and ceramic monolithics, which have very noticeable distortion. The one thing both electrolytics and monolithics have in common is their relatively compact size, achieved in part by use of a very thin dielectric. It’s interesting to see that the high-voltage monolithic has less distortion than it’s low-voltage counterpart, perhaps in part because the HV version has a thicker and/or different dielectric.
While I had known from long-time experience that ceramic and electrolytic caps can muck up the signal path, I never had any data (visual or otherwise) to back it up — until I read about Steve’s experiment a few years ago. As such, I tend to relegate these caps to decoupling and bypassing, and use something else for anything that touches signal, usually polypropylene film.