NE5532 offset nulling circuit (in LTspice IV format)

Version 4
SHEET 1 1108 680
WIRE 336 -208 336 -240
WIRE 336 -112 336 -128
WIRE 416 -112 336 -112
WIRE 336 -96 336 -112
WIRE 416 -96 416 -112
WIRE -224 -48 -224 -80
WIRE -160 -48 -224 -48
WIRE -16 -48 -80 -48
WIRE 128 -48 -16 -48
WIRE -16 -32 -16 -48
WIRE 128 -32 128 -48
WIRE -224 -16 -224 -48
WIRE 128 64 128 48
WIRE 208 64 128 64
WIRE 336 64 288 64
WIRE -16 80 -16 48
WIRE 128 80 128 64
WIRE 96 160 -96 160
WIRE 128 176 128 160
WIRE 192 176 128 176
WIRE 336 192 336 64
WIRE 336 192 256 192
WIRE 368 192 336 192
WIRE 464 192 464 144
WIRE 464 192 432 192
WIRE 480 192 464 192
WIRE 592 192 560 192
WIRE -112 208 -304 208
WIRE 96 208 96 160
WIRE 192 208 96 208
WIRE 0 240 -64 240
WIRE 96 240 96 208
WIRE 96 240 64 240
WIRE -304 272 -304 208
WIRE 336 288 336 192
WIRE 96 304 96 240
WIRE -112 320 -112 288
WIRE -112 320 -208 320
WIRE -64 320 -64 240
WIRE -64 320 -112 320
WIRE -112 336 -112 320
WIRE 592 336 592 192
WIRE -208 352 -208 320
WIRE -304 448 -304 352
WIRE -112 448 -112 416
WIRE 96 448 96 384
FLAG -112 448 0
FLAG 416 -96 0
FLAG -304 448 0
FLAG 592 336 0
FLAG 336 -240 V+
FLAG 224 160 V+
FLAG 336 -16 V-
FLAG 224 224 V-
FLAG -16 80 0
FLAG -224 64 V-
FLAG -224 -160 V+
FLAG 96 448 0
FLAG -96 160 Vin-biased
FLAG 336 288 Vout-biased
FLAG 464 144 Vout-AC
FLAG -208 352 Vin-AC
SYMBOL res 112 -48 R0
SYMATTR InstName R1
SYMATTR Value 1K
SYMBOL res 304 48 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 10K
SYMBOL res -96 304 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R3
SYMATTR Value {10K*b}
SYMBOL res -128 320 R0
SYMATTR InstName R4
SYMATTR Value {10K*(1-b)}
SYMBOL res 576 176 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R5
SYMATTR Value 600
SYMBOL polcap 0 224 M90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C4
SYMATTR Value 10µ
SYMBOL polcap 432 208 M270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName C5
SYMATTR Value 47µ
SYMBOL voltage 336 -112 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL voltage 336 -224 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL voltage -304 256 R0
WINDOW 123 24 124 Left 2
WINDOW 39 0 0 Left 2
WINDOW 0 -121 29 Left 2
WINDOW 3 -173 62 Left 2
SYMATTR InstName Vtest
SYMATTR Value SINE(0 1 300)
SYMBOL Opamps\\opamp2 224 128 R0
SYMATTR InstName U2
SYMATTR Value NE5532
SYMBOL res -32 -48 R0
SYMATTR InstName R6
SYMATTR Value 100
SYMBOL res -240 -32 R0
WINDOW 0 -38 38 Left 2
WINDOW 3 -124 68 Left 2
SYMATTR InstName R7
SYMATTR Value {50K*(1-a)}
SYMBOL res -240 -176 R0
WINDOW 0 -40 41 Left 2
WINDOW 3 -89 71 Left 2
SYMATTR InstName R8
SYMATTR Value {50K*a}
SYMBOL res -176 -64 M90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R9
SYMATTR Value 200K
SYMBOL res 80 288 R0
SYMATTR InstName R10
SYMATTR Value 100K
SYMBOL res 112 64 R0
WINDOW 0 -51 30 Left 2
WINDOW 3 -64 60 Left 2
SYMATTR InstName R11
SYMATTR Value 100K
TEXT -56 -248 Left 2 !.lib NE5532.sub
TEXT -56 -224 Left 2 !.tran 30ms
TEXT 136 464 Left 2 ;R10 is needed for the + input pin bias current in the presence of C4.
TEXT -56 -192 Left 2 !.param a = 0.45
TEXT -320 496 Left 2 ;R3 & R4 are stand-in for a volume pot.
TEXT -184 -128 Left 2 ;R7 & R8 are the Voffset bias pot.
TEXT -56 -168 Left 2 !.param b = 0.9
TEXT 136 488 Left 2 ;Using a fairly large value here for demo purposes to induce a large Voffset.