• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

SPICE model for 6AK5 wanted!

Here is a model for 6AK5 that I have developed. The data I have does not include control grid current, so the model is not accurate in that respect. Also, I dont know if this is 3F4 compatible or not, I have forgotten all the conversions. It works with LTSpice. If it is not 3F4 compatible, then some day I will do a translation, but not today.

* Pentode model based on my investigations
* see Excel spreadsheets BeamDLPentode.xls
* this model therefore uses Korens method for total current, and diode lines.
* similart to Pentode1, but with revised Capture Ratio formula
* R McLean 1 Apr 2008
.Subckt 6AK5 A S G K
+ Params: Ex=1.919796584 Mug=28.62765031 Mus=5.93E+02 Kg1=1241.263033 Kp=87.71075724
+ Kvb=0.001045715 Go=-0.174882604 Kd=5.00E-02 Exd=1.018581504 Exsd=1.106610165
+ C1= -20.45944113 A1=-0.001923837 B1=20.33820425 X1=0.011665792 Y1= 0.000268033 Sr=0.032709138
+ Cgk=4P Cgs=.5P Cga=0.03P Cak=2.8P

* calculate the total space current based on Koren's triode equations,
* but with an equivalent triode plate volatage equal to the pentode Vs + Vp/Mus
En1 n1 0 VALUE={(V(A,K)/Mus+V(S,K))/Kp*LN(1+EXP(Kp*(1/Mug+(V(G,K)-Go)/SQRT(Kvb+(V(A,K)/Mus+V(S,K))**2))))}
Esc sc 0 VALUE={ (PWR(V(n1),Ex)+PWRS(V(n1), Ex))/(Kg1) }

* calculate the plate current capture ratio
Ecr cr 0 Value={If(V(A,K)<=0,0,C1+A1*V(A,K)+B1*((limit(V(A,G),1,1e6)**X1)/(limit(V(S,G),1,1e6)**Y1)))}

* the tentative plate current is total space current multiplied by capture ratio
Ept pt 0 Value={V(sc)*V(cr)}

* calculate the diode line current
Ed d 0 value={Kd*V(A,K)**Exd*V(S,K)**Exsd}

* the actual Plate current is the lesser of pt and d
Ep p 0 value={Min(V(d),V(pt))}
Ga A K value={V(p)}

* calculate the screen current capture ratio
* if Vg <= 0 then the screen gets all the remaining current, otherwise the grid gets some
Escr scr 0 value={Limit(if(V(G,K)>0,1-Sr*V(G,K),1),0,1)}

* screen current is anything not captured by the plate, multiplied by screen capture ratio
Esg sg 0 value={(V(sc)-V(p))*V(scr)}
Gs S K value={V(sg)}

* grid current is anything not captured by the plate or the screen
Gg G K value={V(sc)-v(p)-V(sg)}

* interelectrode capacitances
C1 G K {Cgk}
C2 G S {Cgs}
C3 G A {Cga}
C4 A K {Cak}