[sdiy] (Electrolytic) Capacitors in audio coupling

[Seb Francis]

René Schmitz wrote:
>
> Other than that, I'd like to point out that you should perhaps look 
> into wether you really need those high values at all.  No need to buy 
> an extra bass octave, which your speakers can't reproduce anyway. If 
> you can make inputs of higher impedance you only need smaller caps, 
> and might get away with foil caps. And I think its often that your 
> load is minimum 10k or so, where you get into the region of 680n for a 
> 25Hz lower corner.

I think I do need the values that I'm using as they are matched to the 
requirements of the input and output stages of an audio CODEC.  The 
other place is the input to a THAT VCA, and again I've gone with the 
values the datasheet has suggested.

This is the specific circuit in question:
http://burnit.co.uk/sdiy/stuff/Digi-Mod.pdf
(pages 2, 8-11)

> If you must use the higher values however (think driving 600ohms), you 
> can improve the high frequency behaviour by paralleling a smaller cap 
> to the electrolytic, as its also often done with power supply decoupling.
>

This sounds interesting, so maybe parallel a C0G ceramic?  I could lay 
an extra footprint to be able to try this out.  Would you suggest any 
particular values?

Thanks,
Seb