[sdiy] Electrolytic Caps for Audio Decoupling

[Seb Francis]

Harry Bissell Jr wrote:

> We need to separate the term "Decoupling"
> from the term "Coupling" in regard to capacitor usage. They are not the
> same.
>
Ok, I consider my wrist well and truly slapped !

So continuing on the subject of AC-COUPLING caps ...

>
> Polarity is a big problem. If you know that one DC potential is always 
> higher than
> the other, normal POLARIZED electrolytic caps may be used.
>
In the THAT datasheets and design notes they show polarized caps with 
the negative end connected via a resistor to the IC inputs which are at 
virtual ground.  And in fact many times I have seen polarized caps used 
in places like this where in all likelyhood the polarity will be 
reversed about half of the time.

I'm guessing this may cause some distortion, and certainly degrade the 
polarized cap over time.

>
> If the polarity is unknown, a non-polar electrolytic would be a good 
> choice.
>
This sounds like good advice, but I wonder why this type of cap is not 
more commonly shown on schematics, especially featuring THAT ICs which 
are meant to be pretty high-end audio components.

> Some people like to parallel that electroytic with a film or ceramic 
> cap to
> overcome the self-inductance of the electrolytic cap and increase the
> high frequency performance.
>
> Now you are going into audiophile land...
>
No need to go there .. this will be a compressor for analog drums + 
analog synths :)  I have plenty of audiophile compressors in software if 
I want to compressor a whole mix or something.

Seb