The Sound of Capacitors - Electrolytics

Electrolytic capacitors are not known for their linearity. In the initial article, I presented two curves, one a Tant, and one an Aluminum electrolytic. These were so called "non polarized" devices, and they displayed a lot of hysteresis. Here's the curves:

Neither of these are particularly grand. In discussions with several folks, it was pointed out that these devices really want to be polarized with a DC bias, so I thought I'd run a few curves as a function of DC bias. The part(s) chosen were polarized tantalum capacitors, 5 - 0.47uF 35 volt parts in series (175 volt capability) [Note: I originally reported these as 25V parts to some folks off line; they're indeed 35 volt parts.] Here's the results:

There are a couple of items to note:

• The so-called non-polarized parts with no bias look dangerously like the polarized parts with no bias. That probably tells you "worth" of the non-polarized parts. Don't depend on that characteristic.
• With relatively healthy biasing (100 volts) the hysteresis has disappeared. If you look carefully though, you can note that the characteristics is curved, indicating non-linear operation. Apparently the hysteresis was "hiding" the otherwise non-linear character of these parts.

For high quality audio, these parts are probably best avoided.

Steve