[sdiy] Hand-matching capacitors for filter stages

[Antti Huovilainen]

On Tue, 9 Feb 2010, Tim Stinchcombe wrote:

> Cyril Bateman tried to once-and-for-all end the debate on what/how a cap 
> affects audio quality, by attempting to quantify the distortion etc. 
> that comes from different types. Not all of it may be attributable to 
> the way we use caps in filters, but some of it is doubtless applicable.

I read the bunch yesterday and it was quite illuminating. However, his 
threshold of "bad" distortion from caps is very low: -90dB is enough to 
get it. For comparison, 1V sine into emitter follower with +- 15V rails 
already gives as much distortion (-80dB with +- 9V).

So, just because you've used polyester caps that doesn't mean you need to 
recap every module you've built. Most interesting (filter, vca) modules 
have much higher distortion sources than the very small amount of 2nd/3rd 
harmonic that "badly" built polyester caps produce.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova