[sdiy] DC blocking caps on inputs - or not?

[Gordonjcp]

On Sat, Feb 06, 2016 at 03:37:06AM -0600, mskala at ansuz.sooke.bc.ca wrote:
> On Sat, 6 Feb 2016, Mattias Rickardsson wrote:
> > Another capacitor question popped up:
> > What's your view on having electrolytic caps right at the input of an audio
> > device in order to block DC and/or protect the circuit?
> 
> I think it's not so much a question of "protection," as of allowing you to
> choose the DC bias point of the first stage.  If you don't block DC, then
> anything you connect to that input is going to affect the bias in a
> hard-to-predict way.
> 

This is pretty much it.

> I'd avoid electrolytic caps in this application because they don't
> tolerate reverse voltage, and so it'd become necessary to protect the cap
> from that, one way or another.  Not so much an issue of signal quality.
> 

If you're sticking sufficient voltage and current backwards into the electrolytic capacitor to damage it, you're likely to zap other things as well.  Electrolytics are nowhere near as fragile as people think they are.

-- 
Gordonjcp MM0YEQ