[sdiy] Hand-matching capacitors for filter stages

[thx1138]

On 2/9/10 11:30 AM, "David G. Dixon" <dixon at interchange.ubc.ca> wrote:

>> I often use polystyrene
>> capacitors for filters, since these are widely regarded as the best,
>> and breadboard experiments I've done do tend to support this.
> 
> How are they better, exactly?  Does the filter sound better?  Is the
> filter's transfer function closer to the theoretical?
> 
> I've never used (or even seen) a polystyrene cap, because they are too
> inconvenient to obtain, and I loathe inconvenience.  I've used silvered
> mica, metallized polypropylene, and C0G ceramics, and they all seem to work
> pretty well.  Polystyrene caps are famous for having low leakage, but many
> others are nearly as low.  What specific quality of polystyrene is so
> desirable for filters, and how exactly does this enhance the filter's
> performance?
> 
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Hi David,

Your observations are correct.

I have about 4500 PolyStyrene that are Green epoxy covered I bought back in
1979 from a Hughes Aircraft parking lot sale .

I love polypropylene for the same reasons you described and they survive
rosin flux removal pretty well.

I too have some Silver Mica in small amounts and some ceramics I keep around
just in case. But I am trying to use up some of what I have on hand before I
do another buy.

Most of my LAB parts inventory disappeared from the business when it was
robbed by some thieves back in 1984. They even took the work benches from
the industrial building I was leasing.

They were looking for Gold and electronics in our facility it seems. It cost
me about 250K to replace test equipment and some of the inventory. Some
things were harder to replace like my 1930's Telefunken Microphones and
Enigma machines I restored.

Regards,

Terry