1. Models only the blocks that form a continuous signal chain between the two points (MIC → MAX9814 pre-amp → two op-amp gain stages → output switch).
2. Uses vendor-supplied macromodels where available (MAX9814) and generic ideal op-amp models for the three ADA4807 stages (replace with proper macro-models if you have them).
3. Applies an AC-sweep stimulus so you can view frequency response, plus a quick transient test to see waveform shape at one representative frequency (1 kHz).

Spice
* === Bone Conduction Hearing Aid v2.1 – Simplified Audio Path ===
* Units: V, A, seconds, Farads, Ohms, Henry
*---------------------------------------------------------------
* 1) AC source (simulates acoustic pressure on electret element)
VIN  N_MICIN_GND  0  AC 1 SIN 0 1 1k

* 2) Electret bias resistor (R3 2.2 k nominal)
RBiasMic  N_MICBIAS N_MICIN_GND 2200

* 3) MAX9814 pre-amp (IC4)    
*    Download “MAX9814.SUB” from Maxim → File must be in same dir.
XMAX9814 N_MICIN_GND N_MICBIAS N_MICOUT N_MAXVDD N_MAXGND MAX9814

* 4) Coupling capacitor C1 (1 µF)  
Ccouple1  N_MICOUT N_OP1_IN 1u

* 5) 1st op-amp stage – [U1](https://www.flux.ai/:handle/:documentSlug?fit=U1)  
*    Non-inverting gain set by R11 and R1/1
R11 N_OP1_IN   N_OP1_OUT 100k
Rfb1 N_OP1_OUT N_OP1_FB   10k
EOP1 N_OP1_OUT 0  N_OP1_IN N_OP1_FB  999k

* 6) Coupling / EQ network (C2/1 etc.) – simplified as single cap
Ccouple2  N_OP1_OUT N_OP2_IN 470n

* 7) 2nd op-amp stage – [U2](https://www.flux.ai/:handle/:documentSlug?fit=U2)  
EOP2 N_OP2_OUT 0  N_OP2_IN 0  400k
Rload2 N_OP2_OUT 0 100k

* 8) 3rd op-amp stage – [U3](https://www.flux.ai/:handle/:documentSlug?fit=U3)  
EOP3 N_OP3_OUT 0  N_OP2_OUT 0  200k
Rload3 N_OP3_OUT 0 10k

* 9) Output coupling cap to headphone jack / SW2
Ccouple3  N_OP3_OUT N_SW2 4.7u

*—- Power rails (5 V and 2.5 V virtual rails) ——*
V5   N_MAXVDD 0  5
V25  N_V25    0  2.5

*—- Ground references ——*
.PARAM ac_in=1  
*---------------------------------------------------------------
* AC frequency sweep 20 Hz → 20 kHz, 20 pts/dec
.AC DEC 20 20 20000
.PROBE V(N_SW2)
.PROBE V(N_MICIN_GND)
*---------------------------------------------------------------
* Transient check: 1 ms to 10 ms at 1 kHz
.TRAN 0.01m 10m
.PROBE V(N_SW2) V(N_MICIN_GND)
*---------------------------------------------------------------
.END

1. Place the MAX9814.SUB file (or any other macro-models you add) in the same directory as your project’s exported net-list.
2. Copy the entire block above into the chat after the @simulator keyword, for example:

@simulator
<paste-the-netlist-above>

3. Copilot will parse the net-list and launch the Ngspice engine.
   • The AC analysis returns a Bode plot of magnitude & phase from MK1 to SW2.
   • The TRAN analysis provides the actual waveform at SW2 for a 1 kHz tone.
4. If Ngspice reports missing models:
   • Replace EOPx ideal op-amps with real ADA4807 macromodels once you obtain them.
   • Verify every passive in the list exists (capacitance & resistance values).
5. Rerun @simulator after model fixes; Copilot will display the plots and let you download raw CSV data for further processing.