4P1L triode SPICE model

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After playing for some time with Dmitry’s great DHT composite triode models, I looked at refining the model by matching my own set of curves of the 4P1L in triode-mode. Here is my take on it:

4P1L Triode ModelAnd here is the SPICE model:

*** 4P1L TRIODE ******************************************
* Created on 04/01/2013 10:53 using paint_kit.jar
* www.bartola.co.uk/valves / valves@bartola.co.uk
* Created by Ale Moglia from curve tracer
* Curves image file: 4P1L Triode.jpg
* Data source link: www.bartola.co.uk/valves
*----------------------------------------------------------------------------------
.SUBCKT TRIODE_4P1L 1 2 3 4; Plate Grid K1 K2
+ PARAMS: CCG=3P CGP=4P CCP=2P
+ MU=8.16 KG1=1702 KP=124
+ KVB=533 VCT=0 EX=1.59 RGI=2000
* Vp_MAX=500 Ip_MAX=0.08
* Vg_step=5 Vg_start=5 Vg_count=11
* END PARAMS -----------------------------------------------------------------------
* cathode resistor is (2.1V/650ma) = 3.23 ohm, the pins K1 and K2 are 0.807 ohms from the ends of it
RFIL_LEFT 3 31 0.807
RFIL_RIGHT 4 41 0.807
RFIL_MIDDLE 31 41 1.615
E11 32 0 VALUE={V(1,31)/KP*LOG(1+EXP(KP*(1/MU+V(2,31)/SQRT(KVB+V(1,31)*V(1,31)))))}
E12 42 0 VALUE={V(1,41)/KP*LOG(1+EXP(KP*(1/MU+V(2,41)/SQRT(KVB+V(1,41)*V(1,41)))))}
RE11 32 0 1G
RE12 42 0 1G
G11 1 31 VALUE={(PWR(V(32),EX)+PWRS(V(32),EX))/(2*KG1)}
G12 1 41 VALUE={(PWR(V(42),EX)+PWRS(V(42),EX))/(2*KG1)}
RCP1 1 3 1G
RCP2 1 4 1G
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
D4 6 4 DX ; FOR GRID CURRENT
RG1 2 5 {RGI} ; FOR GRID CURRENT
RG2 2 6 {RGI} ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
*$

Note that the above triode is with paralleled filaments so it’s running at 2.1V and 650mA. Also this model use the 4-element DHT symbol in SPICE.

Looking at Dmitry’s parameters on his model:

*-------------------------------------------------------------------------------
* TRIODE_4P1L_COMPOSITE_5: Russian pentode 4P1L in triode mode.
* Five-element Composite model.
* Created on Wed Mar 16 22:56:00 PST 2005 using tube.model.finder.PaintKIT
* tube data: http://www.klausmobile.narod.ru/testerfiles/4p1l.htm
* http://www.klausmobile.narod.ru/testerfiles/4p1l_vah_10.gif
*-------------------------------------------------------------------------------
.SUBCKT TRIODE_4P1L_COMPOSITE_5 1 2 3 4 ; P G K1 K2
XDHT 1 2 3 4 DHT_COMPOSITE_5
+ PARAMS: CCG=3P CGP=4P CCP=2P RGI=2000 RFILQ=1
+ MU=9.88 EX=1.4 KG1=914 KP=101 KVB=168.5 VCT=0.003 ; Vp_MAX=175.0 Ip_MAX=0.04 Vg_step=2.0
.ENDS
*$

We can see that there is a difference in KP which makes both model to perform different from a linearity point of view. Highly linear triodes have KP above 100. Here are some examples:

  • 6e5P: KP=242
  • 6J11p: KP=276
  • 6J9P: KP=300
  • D3a: KP=475

Despite having a minor difference of 20 (KP=101 – Dmitry’s and KP=121 – Ale’s model)  I found that the models behave differently when driving large signals. The impact of KP is more evident at those extremes of the curves and my model provides a more linear 4P1L representation.

Here is a typical loadline for a 5k6 OT:

4P1L SE Loadline

 

Are you looking for a PSE Spice model? I’ve done my version here by simply doubling the anode current (from 80mA to 160mA maximum) and halving KP parameter:

4P1L PSE model matching curves

Also note that Pa is now doubled to 18W maximum.

Here is the 4-element SPICE composite model:

**** 4P1LPSE ******************************************
* Created on 03/23/2013 08:47 using paint_kit.jar
* www.bartola.co.uk/valves
* Curves image file: 4P1LPSE
* Data source link: 4P1LPSE
*----------------------------------------------------------------------------------
.SUBCKT TRIODE_4P1LPSE 1 2 3 4 ; Plate Grid K1 K2
+ PARAMS: CCG=6P CGP=8P CCP=4P
+ MU=8.16 KG1=851 KP=124
+ KVB=533 VCT=0 EX=1.57 RGI=2000
* Vp_MAX=550 Ip_MAX=0.16
* Vg_step=5 Vg_start=5 Vg_count=14
* END PARAMS -----------------------------------------------------------------------
* cathode resistor is (2.1V/(2x650ma) = 1.615 ohm, the pins K1 and K2 are 0.403 ohms from the ends of it
RFIL_LEFT 3 31 0.403
RFIL_RIGHT 4 41 0.403
RFIL_MIDDLE 31 41 0.807
E11 32 0 VALUE={V(1,31)/KP*LOG(1+EXP(KP*(1/MU+V(2,31)/SQRT(KVB+V(1,31)*V(1,31)))))}
E12 42 0 VALUE={V(1,41)/KP*LOG(1+EXP(KP*(1/MU+V(2,41)/SQRT(KVB+V(1,41)*V(1,41)))))}
RE11 32 0 1G
RE12 42 0 1G
G11 1 31 VALUE={(PWR(V(32),EX)+PWRS(V(32),EX))/(2*KG1)}
G12 1 41 VALUE={(PWR(V(42),EX)+PWRS(V(42),EX))/(2*KG1)}
RCP1 1 3 1G
RCP2 1 4 1G
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
D4 6 4 DX ; FOR GRID CURRENT
RG1 2 5 {RGI} ; FOR GRID CURRENT
RG2 2 6 {RGI} ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
*$

And here is a typical loadline with a 5k6 OT gapped at 60mA:

4P1L PSE Loadline

Hope you enjoy it!

 

 

  

2 thoughts on “4P1L triode SPICE model

  1. Hei Ale,
    thanks for all the effort you put in this. I am planning a headphone amp with this tube and your models will be used in simulating. Just thought it would be nice to know that yor work is appreciated :=
    thanks a lot, harald

    • Harald, many thanks! Just try them and send me your feedback. Would be keen to get how you get on with it. From my experiments. 4P1L PSE is hard to beat!
      Ale

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