GU-50 SPICE Model

It’s been a while indeed. Mostly busy with my day job and family. However, spare time is dedicated to synthesisers – I’m designing and building modules for Eurorack – and playing and listening to music.

I’ve been asked about the GU-50 triode curves. I have misplaced them, however I have something even better to share which is the accurate model created for this great valve.

Here are the pentode curves at different screen voltages with the matching model:

Here are the models for you to use:

***************************************************
.SUBCKT GU50-pentode-300V 1 2 3 4 ; A G2 G1 C;
*      Extract V3.000
* Model created:  4-Jun-2016
* Version 2
*
* Curve tracing and model by Ale Moglia (valves@bartola.co.uk)
* (c) 2016 Bartola Valves
* www.bartola.co.uk/valves
*
* Derk Model
*
X1 1 2 3 4 BTetrodeD  MU=  6.26 EX=1.296 kG1= 380.1 KP=  22.3 kVB =  437.3 kG2=92411.5
+Sc=.81E+01 ap=  .100 w=     0. nu=   .00 lam=    39.4
+ Ookg1mOokG2=.262E-02 Aokg1=.99E-06 alkg1palskg2=.262E-02 be=  .080 als=173.46 RGI=2000
+ CCG1=13.0P  CCG2 = 0.0p CPG1 = 0.0p  CG1G2 = 0.1p CCP=10.0P  ;
.ENDS

****************************************************
.SUBCKT BTetrodeD 1 2 3 4; A G2 G1 C
*
* NOTE: LOG(x) is base e LOG or natural logarithm.
* For some Spice versions, e.g. MicroCap, this has to be changed to LN(x).
*
RE1  7 0  1MEG    ; DUMMY SO NODE 7 HAS 2 CONNECTIONS
E1 7 0 VALUE=
+{V(2,4)/KP*LOG(1+EXP(KP*(1/MU+V(3,4)/SQRT(KVB+V(2,4)*V(2,4)))))}
E2   8 0 VALUE = {Ookg1mOokG2 + Aokg1*V(1,4) - alkg1palskg2/(1 + be*V(1,4))}
E3   9 0 VALUE = {Sc/kG2*V(1,4)*(1+tanh(-ap*(V(1,4)-V(2,4)/lam+w+nu*V(3,4))))}
G1   1 4 VALUE = {0.5*(PWR(V(7),EX)+PWRS(V(7),EX))*(V(8)-V(9))}
G2   2 4 VALUE = {0.5*(PWR(V(7),EX)+PWRS(V(7),EX))/KG2 * (1+ als/(1+be*V(1,4)))}
RCP  1 4  1G      ; FOR CONVERGENCE	A  - C
C1   3 4  {CCG1}   ; CATHODE-GRID 1	C  - G1
C4   2 4  {CCG2}   ; CATHODE-GRID 2	C  - G2
C5   2 3  {CG1G2}   ; GRID 1 -GRID 2	G1  - G2
C2   1 3  {CPG1}  ; GRID 1-PLATE	G1 - A
C3   1 4  {CCP}   ; CATHODE-PLATE	A  - C
R1   3 5  {RGI}   ; FOR GRID CURRENT	G1 - 5
D3   5 4  DX      ; FOR GRID CURRENT	5  - C
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS BTetrodeD

And here is the triode model:

****************************************************
.SUBCKT GU50-triode 1 2 3; A G C;
*      Extract V3.000
* Model created:  4-Jun-2016
*
*
* Curve tracing and model by Ale Moglia (valves@bartola.co.uk)
* (c) 2016 Bartola Valves
* www.bartola.co.uk/valves
*
X1 1 2 3 TriodeK MU=  6.18 EX=1.380 KG1= 448.2 KP=  22.3 KVB=  700. RGI=2000
+ CCG=0.0P  CGP=0.0P CCP=0.0P  ;
.ENDS

****************************************************
.SUBCKT TriodeK 1 2 3; A G C
*
* NOTE: LOG(x) is base e LOG or natural logarithm.
* For some Spice versions, e.g. MicroCap, this has to be changed to LN(x).
*
E1 7 0 VALUE=
+{V(1,3)/KP*LOG(1+EXP(KP*(1/MU+V(2,3)/SQRT(KVB+V(1,3)*V(1,3)))))}
RE1 7 0 1G
G1 1 3 VALUE={0.5*(PWR(V(7),EX)+PWRS(V(7),EX))/KG1}
RCP 1 3 1G    ; TO AVOID FLOATING NODES IN MU-FOLLOWER
C1 2 3 {CCG}  ; CATHODE-GRID
C2 2 1 {CGP}  ; GRID-PLATE
C3 1 3 {CCP}  ; CATHODE-PLATE
D3 5 3 DX     ; FOR GRID CURRENT
R1 2 5 {RGI}  ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS TriodeK

You can download the files from here: