[sdiy] (de)coupling capacitors

[Glen]

At 11:09 AM 7/18/04 , harrybissell wrote:

>Theo made the best point...can you scale the impedances to get the cap
>smaller, and then use a film
>capacitor ? If not, I'd go with NP Lytics.

I agree with practically everything Harry said. In fact, he saved me from
having to write a lengthy post.  ;)

However, there is a potential problem with raising the input impedance of a
circuit to allow for a smaller coupling capacitor at the input. It can
sometimes noticeably increase the amount of background noise. If you aren't
dealing with small signal levels, or if you aren't fussy about a little
extra noise, it might not be a big deal to you. I just wanted to mention
this one possible tradeoff with the smaller input capacitor and the higher
input impedance.

I would probably use the non-polarized electrolytic like Harry suggested,
unless I happened to have a large enough metalized poly capacitor laying
around (and it physically fits the circuitry--they can be quite large.)
Some people would even place a small, high-quality capacitor in parallel
with the large non-polarized electrolytic, in hopes of offsetting some of
the potential distortion in the large electrolytic.


later,
Glen