[sdiy] Hand-matching capacitors for filter stages

[rob]

Hi folks,
I have built a large number of filter "clones" over the last few years, 
ranging from E-mu Systems, ARP to Roland and EMS.
My experience with filter core capacitors...(we always fit high quality 
audio path electrolytic caps from Panasonic).

The use of modern components seems to be a big factor.
An ARP4035 VCF clone compared with an ARP 4034 original I have, sounds 
alot clearer, better frequency response curve and less noise.
The clone has polyester caps not polystyrene, and only 10% matching.
But every component was Modern in the clone.

Wise people say you  must use polystyrene 1% caps...so I have for many 
filters.
A Roland IR3109 filter with polystyrene 1% capacitors sounds alot better 
than the original JP-8.
The detail in the resonance control and the edge of the sound on cutoff 
is way more impressive.
But was that just down to the OTA caps? Yeah probably.

The E-mu Systems SSM2040 LPF and SSM2020 Resonant Filter certainly sound 
smooth with 1% polystyrene caps.

But recently I have questioned this wisdom and fitted 1% matched "green" 
polyester film caps in diode ladders.
Does this sound awful? Well no, they sound brilliant, very "diode" edgy 
and controllable.
I will fit them to a Roland moog SH-3A filter and see how thats sounds 
next week.

So to resolve some of this theory I am building a couple of EMS diode 
filters, to conduct an A-B test.
One with the original unmatched " as old as I can find" 10% ceramics
One with matched 1% "green" polyester film, we will see what the 
difference is!

Perhaps I should also build an ARP 4012 filter with polystyrene 1% caps, 
and compare with the 10% polyester film version I have.
I will post some audio samples on the web site

Regards - Rob
www.emulatorarchive.com