Tried with different MOSFET models, and the one I have for CD4007 performs the best, but still with not enough gain.

There's many bad models for the 2N7000. They often don't work at low currents and all the stuff we use for effects pedals. If you search "Win Hill" 2N7000 or "Winfield Hill" 2N7000 you might find something.

The CD4007 is a *very* different device, much higher resistance.

These models are OK for small signal stuff.

It's a long while since I verified the ROB model.

* Win Hills version of this has M1 without L and W modified

* so Win's relies on default L and W.

.SUBCKT MZVN4106_ZTX 3 4 5

* Nodes D G S

M1 3 2 5 5 MOD1 L=1u W=1u

RG 4 2 343

RL 3 5 6E6

D1 5 3 DIODE1

.MODEL MOD1 NMOS VTO=2.474 RS=1.68 RD=0.0 IS=1E-15 KP=0.296

+CGSO=23.5u CGDO=4.5u CBD=53.5P PB=1 LAMBDA=267E-6

.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222

.ENDS MZVN4106_ZTX

*

* This is my best model so far for low currents (=M2N7000_AVGSS)

*

* Average 2N7000/BS170 device for small signal

* Based on some playing around.

* VTO is in the 1.8 to 2.0V region

* KP is in the 20e-3 to 30e-3 region.

* Originally Zetex Generic (N-channel DMOS, 2n7000, 2n7002 etc)

* CGDO increased from 4.5u to 12.5u to match measurements

.SUBCKT M2N7000_ROB 3 4 5

* Nodes D G S

M1 3 2 5 5 MOD1

RG 4 2 343

RL 3 5 6E6

D1 5 3 DIODE1

.MODEL MOD1 NMOS VTO=1.9 RS=1.68 RD=0.0 IS=1E-15 KP=26e-3

+CGSO=23.5u CGDO=12.5u CBD=53.5P PB=1 LAMBDA=267E-6

+L=1u W=1u

.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222

.ENDS M2N7000_ROB

*