A simulation of the headphone amp to determine the bandwidth yields a 30 dB peak around 75 Hz, at 1 KHz the amplitude is -45 dB. Using an LT1055 produced the expected results, a bandwidth of about 1 MHz. The netlist follows:
Version 4 SHEET 1 880 680 WIRE 0 144 -48 144 WIRE 160 160 64 160 WIRE 208 160 208 128 WIRE 0 176 -16 176 WIRE -16 208 -16 176 WIRE -512 240 -512 224 WIRE -512 240 -576 240 WIRE -576 256 -576 240 WIRE -512 288 -512 240 WIRE -240 288 -336 288 WIRE -144 288 -176 288 WIRE -48 288 -48 144 WIRE -48 288 -64 288 WIRE -16 288 -48 288 WIRE 208 288 208 176 WIRE 208 288 64 288 WIRE 368 288 208 288 WIRE -336 304 -336 288 WIRE 368 304 368 288 WIRE 208 320 208 288 WIRE 160 400 112 400 WIRE 208 400 208 368 WIRE 112 432 112 400 WIRE 208 432 208 416 FLAG -16 208 0 FLAG 368 384 0 FLAG -336 384 0 FLAG -576 256 0 FLAG -512 144 V+ FLAG 208 80 V+ FLAG 32 128 V+ FLAG -512 368 V- FLAG 32 192 V- FLAG 208 512 V- FLAG 112 432 V- FLAG 368 288 out FLAG -336 288 in SYMBOL res 80 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 50k SYMBOL res -48 272 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 35 66 VTop 2 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL res 384 400 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R3 SYMATTR Value 32 SYMBOL res 224 528 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R4 SYMATTR Value 6.8 SYMBOL cap -176 272 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1
SYMBOL voltage -512 128 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 6 SYMBOL voltage -512 272 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 6 SYMBOL voltage -336 288 R0 WINDOW 123 33 59 Left 2 WINDOW 39 0 0 Left 2 WINDOW 3 38 72 Left 2 SYMATTR Value2 AC 0.2 SYMATTR Value "" SYMATTR InstName V3 SYMBOL nmos4 160 80 R0 SYMATTR InstName M1 SYMATTR Value DN2540 SYMBOL nmos4 160 320 R0 SYMATTR InstName M2 SYMATTR Value DN2540 SYMBOL Opamps\\opamp2 32 96 R0 SYMATTR InstName U2 SYMATTR Value MyTL081 TEXT -536 496 Left 2 !.lib C:\\myLTClib\\DN2540.lib TEXT -536 528 Left 2 !.include C:\\myLTClib\\MyTL081.lib TEXT -536 464 Left 2 !.ac dec 100 50 1e5