[sdiy] (de)coupling capacitors

[Theo]

Using a smaller value plastic cap parallel to a elco is what we use for
cathode decoupling in the Tidal tube amps.
At least at a subjective level it seem to work well.

Theo


----- Original Message -----
From: Glen <mclilith at charter.net>
To: harrybissell <harrybissell at prodigy.net>; Theo <t.hogers at home.nl>
Cc: M.A. Koot <makoot at gmx.net>; <synth-diy at dropmix.xs4all.nl>
Sent: Sunday, July 18, 2004 9:50 PM
Subject: Re: [sdiy] (de)coupling capacitors


> 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