* SPICE netlist
R12 N011 vgain {ri}
R13 Hs vx {rc}
RtoneA vx N011 {rtone*apos+1u}
RtoneB p1 vx {rb}
Rboost p2 Hs {rd+1u}
Ro 0 Hs {ro}
C8 p1 0 {c1}
C9 p2 0 {c2}
V1 vin 0 0 AC 1
B1 vovxblt 0 V=V(pre4)*gdsp2 Laplace=(X0blt*exp(-s*Ts) + 1)/(Y0blt*exp(-s*Ts) + 1)
B2 Hz 0 V=-V(vovxblt)*gdsp Laplace=(A2blt*exp(-s*2*Ts) + A1blt*exp(-s*Ts) + 1) / ( B2blt*exp(-s*2*Ts) + B1blt*exp(-s*Ts) + 1)
B3 pre1 0 V=V(vinr)*gx1 Laplace=(b11*exp(-s*Ts) + b10)/(a11*exp(-s*Ts) + 1)
B4 pre2 pre1 V=V(vinr)*gx2 Laplace=(b21*exp(-s*Ts) + b20)/(a21*exp(-s*Ts) + 1)
B5 pre3 N012 V=V(pre2) Laplace=(b31*exp(-s*Ts) + b30)/(a31*exp(-s*Ts) + 1)
B6 N012 0 V=V(vinr)
B7 pre4 0 V=V(pre3)*gx3 Laplace=(b41*exp(-s*Ts) + b40)/(a41*exp(-s*Ts) + 1)
XU1 vinr N006 vcc 0 vgain_pre level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
C3 vinr vin 10n
R5 vinr vbias 1Meg
RdriveA vgain_pre N007 {rgpot*gpos+1u}
R6 N007 N006 {rgser}
RdriveB N008 vgain_pre {rgpot*igpos+1u}
R9 N009 N008 {rgser}
XU2 vbias N004 vcc 0 vgain level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
C7 N004 N009 100n
R10 vgain N004 220k
R8 N010 N006 27k
C6 0 N010 10n
R7 N005 N006 33k
C5 0 N005 10n
V2 vbias 0 4.5
V3 vcc vbias 4.5
C4 vgain_pre N006 100p
D4 vgain N002 1N914
D5 N002 N001 1N914
D2 N001 N003 1N914
D3 N003 vgain 1N914
R11 N001 N004 6.8k
D7 vbias N011 1N914
D6 N011 vbias 1N914
.ac oct 100 20 22050
.step param apos list 0.05 0.5 0.95
.step param bstpos list 0.05 0.5 0.95
.param bpos { 1 - apos}
.param ri {1k}
.param rtone {25k}
.param rboost {50k}
.param ra {ri + apos*rtone}
.param rb {bpos*rtone + rtone/fs}
.param rc {6.8k}
.param rd {rboost*bstpos}
.param ro {100k*1000k/(100k + 1000k)}
.param c1 {10n}
.param c2 {10n}
.param fs 44100
.param Ts {1/fs}
.param aa0 {ro + rc}
.param aa1 {(ro + rd)*rc*c2 + ro*rd*c2}
.param bb1 {(ro+rd)*c2}
.param N0 {aa0}
.param N1 {rb*c1*aa0 + aa1}
.param N2 {rb*c1*aa1}
.param D0 {1}
.param D1 {rb*c1 + c1*aa0 + bb1}
.param D2 {rb*c1*bb1 + c1*aa1}
.param gvx {N2/(N2 + ra*D2)}
.param A0 {N0/N2}
.param A1 {N1/N2}
.param B0 {(N0 + ra*D0)/(N2 + ra*D2)}
.param B1 {(N1 + ra*D1)/(N2 + ra*D2)}
.param gvo {(c2*ro*rd)/(c2*(ro*rd+(ro+rd)*rc))}
.param X0 {1/(c2*rd )}
.param Y0 {(rc + ro)/(c2*(ro*rd+(ro+rd)*rc))}
.param gblt {((A0 + kx*A1 + kx*kx)/(B0 + kx*B1 +kx*kx))}
.param gdsp {gvx*gblt}
.param A1blt {((2*A0-2*kx*kx)/(A0+kx*A1+kx*kx))}
.param A2blt {((A0-kx*A1+kx*kx)/(A0+kx*A1+kx*kx))}
.param B1blt {((2*B0-2*kx*kx)/(B0+kx*B1+kx*kx))}
.param B2blt {((B0-kx*B1+kx*kx)/(B0+kx*B1+kx*kx))}
.param g2blt {(X0 + kx)/(Y0 + kx)}
.param gdsp2 {gvo*g2blt}
.param X0blt {(X0 - kx)/(X0 + kx)}
.param Y0blt {(Y0 - kx)/(Y0 + kx)}
.param kx {2*fs}
.param w1 {1/(33k*10n)}
.param w2 {1/(27k*10n)}
.param a11 = -exp(-w1/fs);
.param g1 = (1.0 - a11)*0.5;
.param b10 = g1;
.param b11 = -g1;
.param a21 = -exp(-w2/fs);
.param g2 = (1.0 - a21)*0.5;
.param b20 = g2;
.param b21 = -g2;
.param rgpot 100k
.param rgser 10k
.param gpos 1.0
.param igpos {1-gpos}
.param gx1 {(rgser + rgpot*gpos)/33k}
.param gx2 {(rgser + rgpot*gpos)/27k}
.param w3 {1/(110k*100p)}
.param w4 {1/((rgser+rgpot*igpos)*100n)}
.param a41 = -exp(-w4/fs);
.param g4 = (1.0 - a41)*0.5;
.param b40 = g4;
.param b41 = -g4;
.param gx3 {220k/(rgser + rgpot*igpos)}
.param a31 = -exp(-w3/fs);
.param g3 = (1.0 + a31)/1.12;
.param b30 = g3;
.param b31 = 0.12*g3;

* LTspice schematic (.asc)
Version 4
SHEET 1 3248 5680
WIRE 328 -2824 168 -2824
WIRE 456 -2824 392 -2824
WIRE 600 -2824 520 -2824
WIRE 168 -2712 168 -2824
WIRE 344 -2712 168 -2712
WIRE 472 -2712 408 -2712
WIRE 600 -2712 600 -2824
WIRE 600 -2712 536 -2712
WIRE 168 -2632 168 -2712
WIRE 168 -2456 168 -2552
WIRE 344 -2456 168 -2456
WIRE 600 -2456 600 -2712
WIRE 600 -2456 424 -2456
WIRE -360 -2344 -392 -2344
WIRE 376 -2312 344 -2312
WIRE 344 -2232 344 -2312
WIRE -1144 -2216 -1336 -2216
WIRE -1016 -2216 -1080 -2216
WIRE -760 -2216 -936 -2216
WIRE -696 -2216 -760 -2216
WIRE -552 -2216 -616 -2216
WIRE -392 -2216 -392 -2344
WIRE -392 -2216 -472 -2216
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WIRE 168 -2216 72 -2216
WIRE 312 -2216 168 -2216
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WIRE 600 -2200 376 -2200
WIRE 664 -2200 600 -2200
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WIRE -392 -2104 -568 -2104
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WIRE 568 -1832 440 -1832
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WIRE -776 -1672 -808 -1672
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WIRE 600 -1336 600 -1448
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WIRE 600 -1208 552 -1208
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WIRE 600 -1176 600 -1208
WIRE -1624 -1096 -1624 -1176
WIRE -1256 -1048 -1256 -1192
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WIRE 600 -1000 600 -1112
WIRE 600 -1000 200 -1000
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WIRE 904 -1000 600 -1000
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WIRE 904 -984 904 -1000
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WIRE -1256 -840 -1256 -968
WIRE -1624 -744 -1624 -856
WIRE -968 1112 -1064 1112
WIRE 392 1112 296 1112
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WIRE -1064 1192 -1064 1112
WIRE 296 1192 296 1112
WIRE 1528 1208 1528 1128
WIRE -1064 1352 -1064 1272
WIRE -968 1352 -1064 1352
WIRE 296 1384 296 1272
WIRE 1528 1400 1528 1288
WIRE -1064 1432 -1064 1352
WIRE 296 1576 296 1464
WIRE -1064 1592 -1064 1512
WIRE -984 2008 -1080 2008
WIRE -1080 2088 -1080 2008
WIRE -1080 2248 -1080 2168
WIRE -1016 2600 -1112 2600
WIRE -1112 2680 -1112 2600
WIRE -1112 2840 -1112 2760
FLAG 904 -984 0
FLAG 8 -1720 vgain
FLAG 952 -1448 Hs
FLAG -1256 -840 0
FLAG -1144 -1192 vin
FLAG 296 -1448 vx
FLAG 152 -1240 p1
FLAG 552 -1208 p2
FLAG -1080 2248 0
FLAG -984 2008 vovxblt
FLAG -1112 2840 0
FLAG -1016 2600 Hz
FLAG -1064 1592 0
FLAG -968 1352 pre1
FLAG -968 1112 pre2
FLAG 392 1112 pre3
FLAG 296 1576 0
FLAG 1624 1128 pre4
FLAG 1528 1400 0
FLAG -664 -1800 0
FLAG -632 -2008 vcc
FLAG -1048 -1880 vin
FLAG -776 -1672 vbias
FLAG 344 -2104 0
FLAG 376 -2312 vcc
FLAG 280 -2184 vbias
FLAG -1336 -2040 0
FLAG 664 -2200 vgain
FLAG -1624 -744 0
FLAG -1592 -984 vbias
FLAG -1448 -1176 vcc
FLAG -840 -1880 vinr
FLAG -360 -2344 vgain_pre
FLAG 568 -1832 vbias
SYMBOL res 168 -1736 R90
SYMATTR InstName R12
SYMATTR Value {ri}
SYMBOL res 504 -1464 R90
SYMATTR InstName R13
SYMATTR Value {rc}
SYMBOL res 216 -1480 R180
SYMATTR InstName RtoneA
SYMATTR Value {rtone*apos+1u}
SYMBOL res 216 -1288 R180
SYMATTR InstName RtoneB
SYMATTR Value {rb}
SYMBOL res 616 -1240 R180
SYMATTR InstName Rboost
SYMATTR Value {rd+1u}
SYMBOL res 920 -1176 R180
SYMATTR InstName Ro
SYMATTR Value {ro}
SYMBOL cap 184 -1176 R0
SYMATTR InstName C8
SYMATTR Value {c1}
SYMBOL cap 584 -1176 R0
SYMATTR InstName C9
SYMATTR Value {c2}
SYMBOL voltage -1256 -1064 R0
SYMATTR Value2 AC 1
SYMATTR InstName V1
SYMATTR Value 0
SYMBOL bv -1080 2072 R0
SYMATTR InstName B1
SYMATTR Value V=V(pre4)*gdsp2 Laplace=(X0blt*exp(-s*Ts) + 1)/(Y0blt*exp(-s*Ts) + 1)
SYMBOL bv -1112 2664 R0
SYMATTR InstName B2
SYMATTR Value V=-V(vovxblt)*gdsp Laplace=(A2blt*exp(-s*2*Ts) + A1blt*exp(-s*Ts) + 1) / ( B2blt*exp(-s*2*Ts) + B1blt*exp(-s*Ts) + 1)
SYMBOL bv -1064 1416 R0
SYMATTR InstName B3
SYMATTR Value V=V(vinr)*gx1 Laplace=(b11*exp(-s*Ts) + b10)/(a11*exp(-s*Ts) + 1)
SYMBOL bv -1064 1176 R0
SYMATTR InstName B4
SYMATTR Value V=V(vinr)*gx2 Laplace=(b21*exp(-s*Ts) + b20)/(a21*exp(-s*Ts) + 1)
SYMBOL bv 296 1176 R0
SYMATTR InstName B5
SYMATTR Value V=V(pre2) Laplace=(b31*exp(-s*Ts) + b30)/(a31*exp(-s*Ts) + 1)
SYMBOL bv 296 1368 R0
SYMATTR InstName B6
SYMATTR Value V=V(vinr)
SYMBOL bv 1528 1192 R0
SYMATTR InstName B7
SYMATTR Value V=V(pre3)*gx3 Laplace=(b41*exp(-s*Ts) + b40)/(a41*exp(-s*Ts) + 1)
SYMBOL Opamps\\UniversalOpamp2 -664 -1896 R0
SYMATTR InstName U1
SYMBOL cap -904 -1896 R90
SYMATTR InstName C3
SYMATTR Value 10n
SYMBOL res -824 -1832 R0
SYMATTR InstName R5
SYMATTR Value 1Meg
SYMBOL res -456 -2232 R90
SYMATTR InstName RdriveA
SYMATTR Value {rgpot*gpos+1u}
SYMBOL res -600 -2232 R90
SYMATTR InstName R6
SYMATTR Value {rgser}
SYMBOL res -216 -2232 R90
SYMATTR InstName RdriveB
SYMATTR Value {rgpot*igpos+1u}
SYMBOL res -40 -2232 R90
SYMATTR InstName R9
SYMATTR Value {rgser}
SYMBOL Opamps\\UniversalOpamp2 344 -2200 R0
SYMATTR InstName U2
SYMBOL cap 72 -2232 R90
SYMATTR InstName C7
SYMATTR Value 100n
SYMBOL res 440 -2472 R90
SYMATTR InstName R10
SYMATTR Value 220k
SYMBOL res -1032 -2088 R270
SYMATTR InstName R8
SYMATTR Value 27k
SYMBOL cap -1144 -2088 R270
SYMATTR InstName C6
SYMATTR Value 10n
SYMBOL res -1032 -2200 R270
SYMATTR InstName R7
SYMATTR Value 33k
SYMBOL cap -1144 -2200 R270
SYMATTR InstName C5
SYMATTR Value 10n
SYMBOL voltage -1624 -952 R0
SYMATTR InstName V2
SYMATTR Value 4.5
SYMBOL voltage -1624 -1112 R0
SYMATTR InstName V3
SYMATTR Value 4.5
SYMBOL cap -568 -2120 R90
SYMATTR InstName C4
SYMATTR Value 100p
SYMBOL diode 520 -2840 R90
SYMATTR InstName D4
SYMATTR Value 1N914
SYMBOL diode 392 -2840 R90
SYMATTR InstName D5
SYMATTR Value 1N914
SYMBOL diode 344 -2696 R270
SYMATTR InstName D2
SYMATTR Value 1N914
SYMBOL diode 472 -2696 R270
SYMATTR InstName D3
SYMATTR Value 1N914
SYMBOL res 152 -2648 R0
SYMATTR InstName R11
SYMATTR Value 6.8k
SYMBOL diode 360 -1848 R90
SYMATTR InstName D7
SYMATTR Value 1N914
SYMBOL diode 312 -1704 R270
SYMATTR InstName D6
SYMATTR Value 1N914