* SPICE netlist
V3 VCC 0 12
V4 VSS 0 -12
V5 V_accent 0 {V_acc}
R55 N001 V_accent 33k
C20 N005 noise 22n
R65 VCC N005 2Meg
Q6 N002 N005 P001 0 BC546B
R66 P001 0 100
C21 N002 0 1.5n
C22 N001 0 1.5n
C23 N003 N001 1.5n
D3 N001 N002 1N4148
C9 N010 noise 1n
C10 N004 N003 1.5n
R34 N003 N006 2.7k
R35 N004 0 68k
Q13 VCC N004 N006 0 BC546B
R36 N006 VSS 22k
C11 808_orig N006 470p
C14 N011 N010 1n
R57 N010 transistor 2.7k
R58 N011 0 68k
Q17 VCC N011 transistor 0 BC546B
R59 transistor VSS 22k
V6 noise 0 AC 1
XU3 N008 N009 VCC VSS sallen_key TL074 ;pnba In+)In-)V+)V-)OUT
C1 N007 noise 1n
C2 N008 N007 1n
R1 sallen_key N007 18k
R2 0 N008 18k
R3 N009 sallen_key {Rf}
R4 N009 0 4.7k
.ac dec 100 1 20000
.inc TL074.mod
;.step param X list 100 25k 50k 250k 500k
;.step param V_acc list 1 2 5 7 10
.param V_acc=10
;.step param Rf list 7k 8.2k 8.5k 9k 10k
.param Rf=8.2k

* LTspice schematic (.asc)
Version 4
SHEET 1 2624 2000
WIRE -256 -984 -384 -984
WIRE 224 -824 224 -856
WIRE -384 -776 -544 -776
WIRE -336 -776 -384 -776
WIRE -256 -776 -256 -984
WIRE -256 -776 -272 -776
WIRE -192 -776 -256 -776
WIRE -80 -776 -128 -776
WIRE -32 -776 -80 -776
WIRE 80 -776 32 -776
WIRE 160 -776 80 -776
WIRE -80 -744 -80 -776
WIRE 80 -744 80 -776
WIRE -656 -728 -656 -792
WIRE -656 -728 -688 -728
WIRE -608 -728 -656 -728
WIRE -384 -728 -384 -776
WIRE -256 -728 -256 -776
WIRE 336 -728 224 -728
WIRE 224 -712 224 -728
WIRE 224 -712 192 -712
WIRE 992 -680 912 -680
WIRE 1232 -680 1072 -680
WIRE 224 -600 224 -632
WIRE -80 -584 -80 -664
WIRE 192 -584 192 -712
WIRE 192 -584 -80 -584
WIRE 832 -504 784 -504
WIRE 912 -504 912 -680
WIRE 912 -504 896 -504
WIRE 928 -504 912 -504
WIRE 1040 -504 992 -504
WIRE 1104 -504 1040 -504
WIRE 1232 -488 1232 -680
WIRE 1232 -488 1168 -488
WIRE 1312 -488 1232 -488
WIRE 1040 -472 1040 -504
WIRE 1104 -472 1088 -472
WIRE 224 -392 224 -424
WIRE -192 -344 -272 -344
WIRE -80 -344 -128 -344
WIRE -32 -344 -80 -344
WIRE 80 -344 32 -344
WIRE 160 -344 80 -344
WIRE 1088 -328 1088 -472
WIRE 1088 -328 1072 -328
WIRE 1104 -328 1088 -328
WIRE 1232 -328 1232 -488
WIRE 1232 -328 1184 -328
WIRE -80 -312 -80 -344
WIRE 80 -312 80 -344
WIRE 1072 -312 1072 -328
WIRE 336 -296 224 -296
WIRE 224 -280 224 -296
WIRE 224 -280 160 -280
WIRE 224 -168 224 -200
WIRE -80 -152 -80 -232
WIRE 160 -152 160 -280
WIRE 160 -152 -80 -152
FLAG -1040 696 0
FLAG -1312 696 0
FLAG -1312 616 VCC
FLAG -1040 616 VSS
FLAG -848 712 0
FLAG -848 632 V_accent
FLAG -752 -728 noise
FLAG -656 -872 VCC
FLAG -544 -600 0
FLAG -384 -664 0
FLAG -256 -664 0
FLAG -464 -984 V_accent
FLAG -272 -344 noise
FLAG 224 -856 VCC
FLAG 224 -600 VSS
FLAG 80 -664 0
FLAG 224 -424 VCC
FLAG 224 -168 VSS
FLAG 80 -232 0
FLAG 336 -296 transistor
FLAG -32 1000 0
FLAG -32 920 noise
FLAG 1136 -456 VCC
FLAG 1136 -520 VSS
FLAG 784 -504 noise
FLAG 1072 -232 0
FLAG 1040 -392 0
FLAG 1312 -488 sallen_key
FLAG 400 -728 808_orig
SYMBOL voltage -1312 600 R0
SYMATTR InstName V3
SYMATTR Value 12
SYMBOL voltage -1040 600 R0
SYMATTR InstName V4
SYMATTR Value -12
SYMBOL voltage -848 616 R0
SYMATTR InstName V5
SYMATTR Value {V_acc}
SYMBOL res -368 -1000 R90
SYMATTR InstName R55
SYMATTR Value 33k
SYMBOL cap -688 -744 R90
SYMATTR InstName C20
SYMATTR Value 22n
SYMBOL res -672 -888 R0
SYMATTR InstName R65
SYMATTR Value 2Meg
SYMBOL npn -608 -776 R0
SYMATTR InstName Q6
SYMATTR Value BC546B
SYMBOL res -560 -696 R0
SYMATTR InstName R66
SYMATTR Value 100
SYMBOL cap -400 -728 R0
SYMATTR InstName C21
SYMATTR Value 1.5n
SYMBOL cap -272 -728 R0
SYMATTR InstName C22
SYMATTR Value 1.5n
SYMBOL cap -128 -792 R90
SYMATTR InstName C23
SYMATTR Value 1.5n
SYMBOL diode -272 -792 R90
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL cap -128 -360 R90
SYMATTR InstName C9
SYMATTR Value 1n
SYMBOL cap 32 -792 R90
SYMATTR InstName C10
SYMATTR Value 1.5n
SYMBOL res -96 -760 R0
SYMATTR InstName R34
SYMATTR Value 2.7k
SYMBOL res 64 -760 R0
SYMATTR InstName R35
SYMATTR Value 68k
SYMBOL npn 160 -824 R0
SYMATTR InstName Q13
SYMATTR Value BC546B
SYMBOL res 208 -728 R0
SYMATTR InstName R36
SYMATTR Value 22k
SYMBOL cap 400 -744 R90
SYMATTR InstName C11
SYMATTR Value 470p
SYMBOL cap 32 -360 R90
SYMATTR InstName C14
SYMATTR Value 1n
SYMBOL res -96 -328 R0
SYMATTR InstName R57
SYMATTR Value 2.7k
SYMBOL res 64 -328 R0
SYMATTR InstName R58
SYMATTR Value 68k
SYMBOL npn 160 -392 R0
SYMATTR InstName Q17
SYMATTR Value BC546B
SYMBOL res 208 -296 R0
SYMATTR InstName R59
SYMATTR Value 22k
SYMBOL voltage -32 904 R0
SYMATTR Value AC 1
SYMATTR InstName V6
SYMBOL Opamps\\opamp2 1136 -424 M180
SYMATTR InstName U3
SYMATTR Value TL074
SYMBOL cap 896 -520 R90
SYMATTR InstName C1
SYMATTR Value 1n
SYMBOL cap 992 -520 R90
SYMATTR InstName C2
SYMATTR Value 1n
SYMBOL res 1088 -696 R90
SYMATTR InstName R1
SYMATTR Value 18k
SYMBOL res 1056 -376 R180
SYMATTR InstName R2
SYMATTR Value 18k
SYMBOL res 1088 -312 R270
SYMATTR InstName R3
SYMATTR Value {Rf}
SYMBOL res 1056 -328 R0
SYMATTR InstName R4
SYMATTR Value 4.7k