model for 12AY7
Try this.
*
* model for one half of 12AY7
*
* heater not included
* Data extracted 16 June 2005
* from ElectroHarmonix 6072A/12AY7EH tube
*
.SUBCKT 12AY7 A G K
+ PARAMS: EX=1.18296637295072 MU=41.7794590897682 KG1=1283.6566442837 KP=328.825557514402 KVB=2847.72219152647
+ Go=0.34371558686874 KG=0.000213922190232166 AG=0.874211243853364 BG=0
+ CCG=1.3P CGP=1.3P CCP=0.6P
E1 4 0 VALUE={V(A,K)/KP*LN(1+EXP(KP*(1/MU+(V(G,K)-Go)/SQRT(KVB+V(A,K)*V(A,K)))))}
G1 A K VALUE={ (PWR(V(4),EX)+PWRS(V(4), EX))/(KG1) }
RCP A K 1G
G2 G K VALUE = {IF(V(G,K)>0,{Kg}*((({Ag}+V(A,K))/({Bg}+V(A,K)))**4)*V(G,K)**1.5,0)}
C1 G K {CCG} ; CATHODE GRID
C2 G A {CGP} ; GRID-PLATE
C3 A K {CCP} ; CATHODE-PLATE
.ENDS 12AY7