[sdiy] electrolytic coupling capacitors

[Glen]

At 04:12 PM 10/31/04 , blitz wrote:

>I'm building a small mixer with gain and need to couple the the 
>output to remove DC.  From circuit analysis I need a 10uF cap in 
>series on the inputs and output to remove the DC offset.  10uF is 
>pretty large, so the only available caps I have are electrolytic with 
>polarity.  Can I use an electrolyitic in place of a non-polarity 
>coupling capacitor?  How do I know which end the +/- should be 
>connected to?

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. 

Here's a link for a 10uF Mylar cap, in case you want to pursue that route:

http://mcm.newark.com/NewarkWebCommerce/mcm/en_US/endecaSearch/partDetail.js
p?SKU=31-0330&N=4

I'm sure you can also find these through other vendors. This is just the
first reference I found.

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.

Personally, for a "basic" mixer, I would probably go with electrolytics. If
I wanted to build some really nice preamp, I might experiment with the
large valued mylar caps.


later,
Glen