[sdiy] AC coupling caps on MS20 clone

[Andre Majorel]

On 2010-07-30 09:48 -0700, David G. Dixon wrote:

> > Cumulative DC offset in the signal path would be a reason
> > for me to want optional AC coupling in an input.
> 
> That's easy enough to do.  I was actually more interested in
> the possible requirement of a cap between the HP and LP
> sections of the filter...?

CV bleed ? The KORG35 MS-20 has plenty. Not easy to apportion
blame between filters and VCA, though, with that hard-wired
signal path...

> > Combined with input impedance, the coupling cap forms a
> > high-pass filter. The value depends on the lowest frequency
> > you want to pass. For example, a 0.1 uF cap coupled to a
> > typical 100K input impedance will cut-off frequencies at
> > 16Hz and lower. Most any non-polar type ought to work.
> 
> Yes.  I usually use 474 (0.47uF) Z5U ceramic caps from Epcos
> for this purpose.  I guess this would preclude using the
> filter as a sine LFO.

A Z5U is probably the worst possible cap to put in a signal path
from a fidelity POV. As we all know, all the best synths have
low THD, right ? :-D

-- 
André Majorel http://www.teaser.fr/~amajorel/