[sdiy] Filters

[harrybissell]

OTA might be more 'high tech' but also a lot harder to control. There is time
delay through the OTA (not much but in a feedback loop it could be enough
to notice)... OTA has limited signal handling capacity, high offset voltage
etc...

Where the LED/Photocell might work just fine, and for maybe $.50 (usa)

I did my Aries filter with the photocell method... using the "Analog
Multiplier"
circuit from NAtional Semiconductor AN-20 (replaced the incandescent lamp
with LED to make it 'hi-tech' :^)

H^) harry

jbv wrote:

> >
> > >Is there a (easy) way to modify this VC-BPF design :
> > >http://www.cgs.synth.net/modules/cgs35_syntha_vcf.html
> > >to add VC-Q to it ?
> >
> > Replace the Q pot with a LDR+LED (and 1k resistor parallel to the LDR) ?
>
> Mmh... I guess there my be a slighly more hi-tech, OTA-based
> solution...
>
> Thanks anyway,
> JB