Simple 12 db low pass filter.
This filter use 2 BC547 NPN transistor and a stereo 100k pot
for the cutoff, instead of the pot. it's possible to use 2 photo resistor.
This filter is calibrated for 5v use but also 9\12 volt for simple application.
I've develop it with Peppo at LEP lab. in Milano.
I use it in this 6 bit noise generator, video.
Val Pastel made this filter audio test listen
A small revision for the 12 db filter, this schematics is calibrated for 12 volt use.
Here an High Pass version of the same filter.