Capacitor questions

[Bill Layer]

 Hi Chris, here's two cents worth:

I am breadboarding a diode ladder filter and have bought polystyrene
>and
>> polypropylene capacitors for the project based on what I have been
>> reading on various diy web sites (thanks a million to those of you who
>> put those up BTW!).

>From my experience in high-end audio, I can make a recomendation. I have
used polystyrene caps frequently in circuit locations requiring stable,
critical value. One example of this is the RIAA eq. circuit in a
preamplifer. It is mandatory to maintain <.5% total error, if your curve is
to be correct, and polystyrenes are found almost exclusively in this
application. If I was constructing a high-precision filter, this would be
my choice. The only real detractors here are the fragility of the parts, so
dont over solder them.

Also, a word on metallized polypropylines. Great performance, small
package, self-healing properties (you can drill a hole through one, and it
will self heal most of the time) but boy do they sound bad in high-end
systems. Probably fine  for guitar amps (especially for their ruggedness)
but in the music signal path, they sound well, like grinding metal. Regular
polyprops are a little more neutral. BTW, don't get 'sold' on Sprague
Orange Drops, they are FINE but nothing AMAZING...

Some really fine poly pro/sty caps come from Reliable Capacitor in
California. Call for their catalog! PSST Eric Barbour; do you have that
number handy? Perhaps from a GA.

Hope I've not muddied the waters for you.>
Bill Layer
Sales Technician
<b.layer at vikingelectronics.com>

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