Pooh Bear wrote:

Strange that almost every single high end recording console uses electrolytics for coupling then ?

Because in the solid-state world there isn't much choice. And one of the
big problems with the early solid-state world is that people adopted the
usual single-ended capacitively-coupled designs that were common with tubes.
Since input impedances were so low, massive caps were required, and so of
course electrolytics turn up.

If somebody made a film cap that was almost as small as an electrolytic and
in the same price range, I don't think you'd see any high end recording
consoles still using electrolytics.

All ceramics aren't bad btw. The ones with low-K dielectrics like NPO don't suffer the dielectric
non-linearity You'd only use them for feedback or small value caps in EQ sections though. Not good for
any more than 330-470 pF in practice..

I really want to know more about ceramic caps... I used to have a strong
anti-ceramic bias until I tried some of the newer COG types which are less
microphonic by a long shot. I want to thank John Hardy for turning me on
to some of the better quality ceramics today. I have used them as coupling
caps in very high-Z circuits and have actually been pleased with the
performance compared with most of the film caps.

The 'rectification effect' in electrolytics only appears AFAIK when a reverse voltage of around 0.5 V
is applied. Keep the reverse volts due to an a.c. signal below that and it doesn't happen. That
*doesn't* mean restricting the a.c. signal value to below 0.5 V though. Think 'potential divider' and
use large value caps. I commonly use 100uF for outputs and 10uF for inputs where Zin is = 10k ohm.

Right. Our question is whether there might be some other nonlinear effects
in addition to this one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."