[sdiy] EFM VCF6

[harrybissell]

Why SURE I do...

I used polystyrene, but they are hard to find in sizes larger than .01uF

Polycarbonate or polypropylene are good choices.

I'd try to match the diodes. You could measure forward voltage at maybe
200uA or so... or just use the diode scale on some meters.  You have to match
in horizontal pairs only.

Failure to match can give a nasty DC bounce when you sweep the control
voltage (the sound might actually drop right OUT momentarily).

The resonance feedback blocking cap (C9 in my schematic) needs to be
MUCH larger... like 100uF to get full resonance down to low frequencies.

Its tied for my favorite EFM filter

H^) harry

Tom Arnold wrote:

> I betcha Harry has some good pointers on this...
>
> I'm ordering caps to stuff a bunch of EFM boards and in fact am right now
> try to select the caps for the VCF6 diode ladder.
>
> After reading Harry's cap information I think I've settled on some caps from
> Mouser.  505-MKP20.1/100/5 which is a Metallized Polypropylene cap.  I was
> looking for a Polycarbonate cap but they seem to be more rare then Polystyrenes
> ( which I have found are being made by several companies right now, not just
> one always-rumored-to-be-stopping company ).
>
> The schematic for the VCF6 ( new and improved instructions even! ) is
> http://www.ele4music.com/pdfs/vcf6c.pdf
>
> I figure this is probably a no brainer...
>
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