Mura Filter

From the Japanese term for the waste of uneveness this filter will create an uneven distortion of the resonance structure both from the transistor and from the diode in the feedback path.  Connections are described in the picture.  Values can be changed somewhat to match standard values.  RS is a rail splitter.  Saving the other side for an LFO to modulate the Fco.  Have not built this yet but it looks pretty cool in the simulator.

Falstad circuit simulator code:


$ 1 5.0E-6 0.9891409633455756 50 5.0 50
r 336 320 272 320 0 4700000.0
c 336 224 336 192 0 1.0E-9 0.00268564673175871
c 432 224 432 192 0 1.0E-9 -1.876367065692067
r 272 320 272 368 0 47000.0
c 272 320 224 320 0 1.0000000000000001E-7 -2.4144869775373956
174 336 192 432 176 0 100000.0 0.9059 Q 100k
a 336 336 432 336 0 15.0 -15.0 1000000.0
w 336 224 336 240 0
w 336 288 336 320 0
w 432 224 432 240 0
w 432 288 432 336 0
g 336 352 336 368 0
g 272 368 272 384 0
O 432 336 432 368 0
174 336 192 240 176 0 100000.0 0.9257000000000001 Fco 100k
g 240 192 240 208 0
w 288 176 336 192 0
R 224 320 192 320 0 2 100.0 5.0 0.0 0.0 0.5
r 336 288 384 288 0 2000000.0
r 384 288 432 288 0 2000000.0
g 384 240 384 224 0
c 384 288 384 240 0 1.0E-11 -0.939194425306891
w 384 176 336 192 0
w 432 240 432 288 0
w 336 240 336 288 0
w 336 160 336 192 0
w 448 288 432 288 0
174 336 160 432 160 0 1000000.0 0.005 Resistance
d 464 160 464 192 1 0.805904783
w 384 144 336 160 0
w 432 160 464 160 0
w 464 192 464 288 0
w 464 288 448 288 0
t 288 128 288 160 0 1 0.45948822583066745 0.4568213771495246 100.0
w 272 160 240 160 0
w 240 160 240 192 0
w 304 160 336 192 0
R 288 96 288 64 0 1 40.0 3.0 2.0 0.0 0.5
174 288 96 304 128 0 1000000.0 0.10400000000000001 Resistance
w 304 112 288 96 0
o 13 4 0 34 20.0 9.765625E-5 0 -1

Note the resonance wave form has a slight sawtooth edge as well as only oscillating on the positive cycle of the square wave.