[sdiy] electrolytic coupling capacitors

[Harry Bissell Jr]

--- Glen <mclilith at charter.net> wrote:


> Just in case you didn't know, you can actually
> purchase mylar caps in the
> 10uF range. They're much larger physically, and they
> cost more than an
> electrolytic, but you don't have to worry about
> polarity. Some people also
> say that they sound better. There are supposed to be
> some quirky nonlinear
> properties involved with electrolytics. 

Well... there are also quirky properties of Mylar
caps.
Mylar is not free of Dielectric Absorption... that
will
cause frequency dependant distortion which you
probably
will NOT notice... like most Audiophile effects :^P

> You can also get non-polarized electrolytics, but
> these are really two
> polarized electrolytics wired in series, one "turned
> around backwards"
> compared to the other one. Since your signal is then
> going through two
> electrolytics, I would expect possibly more signal
> corruption than with the
> polarized variety.

Probably not true.  There should be no greater effects
with a non-polar electrolytic than with a polar
unit...especially if you really NEED a non-polar
because of unknown or unpredictable polarity. Some
folk like to use two polar lytics, back to back...with
a
bias viltage to the center tap...often the most
negative supply. That of course means that the most
negative supply better be REALLY clean (noise free) or
youi are shooting yourself in the foot !!!

Capacitor selection is a series of trade-offs. In
general, the film varieties outpterform the
electrolytics... but for low level (low ripple
current)
apps the electrolytics are the usual choice.

Of course if you are clever, you design your circuits
at a high enough imprdance that the caps scale into
small, easily obtained values.  

Good luck, your mileage may vary :^P

H^) harry