vcf 8e

[harrybissell at prodigy.net]

I'd go with a polystyrene of polypropylene cap for
C3,C4,C6,C7.  You can get some from mouser
Xicon Axial or Radial (whichever fits the holes)
.002uF = 2000pF
5% or better.

The closer the match the easier it will be to get to
higher "Q" (resonance) values.

R26,29,31,34 10K and R27,28,32,33 220 ohm could benefit
from 1% resistors. Same for the other 1/2 of the filter.
Same reason as above... The two stages of each filter
should match well, and you probably get less offset voltage (read thump from CV).

C5 and C8 are coupling capacitors (not smoothing) they should be Bipolar Electrolytic (since you cannot predict which way they will be charged... especially when patched in a modular... mouser has Rubycon type BIW caps
they have a 47uF for $1.53 (if you go smaller with these caps you limit low frequency response. But if you assume that the load that you plug this into is 10K ohms or larger, 10uF would get you response down to 3Hz... so 10uF is probably big enough !!!!

Do NOT use tantalums for C5 and C8 (a BAAD thing)

H^)   call anytime....


 ---- On Feb 17 mark scetta <n0nspaz at loa.com> wrote: 
> harry,
> 
> although i'm still waiting on  a couple of parts to finish up the LFO8a, 
> i'm looking ahead to possibly doing the vcf8e 
> http://www.geocities.com/efm_gc/cam/vcf8e.html
> i searched the DIY archives and didn't come up with any real issues with 
> this circuit, but i wanted to consult you first. let me know if you have 
> any thoughts on it.
> 
> if you could also help with choosing the best capacitors for the job 
> (besides the 2 smoothing electrolytics C5 & C8 which i'm familiar with now) 
> i would appreciate it.
> 
> thanks!
> mark