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Vacuum Tube SPICE Models

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Joined 2004
Paid Member
Linearity and noise performance mainly. It's designed to operate at relatively high currents (recommended up to 15mA) and linearity is not great at low currents. I also want to run them in the high transconductance region of their characteristic curves, I use them in low noise phono stages..
 

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Linearity and noise performance mainly. It's designed to operate at relatively high currents (recommended up to 15mA) and linearity is not great at low currents. I also want to run them in the high transconductance region of their characteristic curves, I use them in low noise phono stages..

Interesting. What plate/cathode voltage are you using.

For my application linearity is not a big issue since the signal level is small and there is global NFB. My plan is to run it at 100V Vak, -1.6 Vgc and Ia of 1mA which still gives a gm of 20mA/V.

Cheers

Ian
 
Code:
.SUBCKT 6973  1 2 3 4 ; A G2 G1 C (Pentode)
* RCA data sheet
* library format: LTSpice 14-Nov-2009
+PARAMS: MU=13.58 EX=1.350 KG1=1142.2 KG2=4500 KP=27.70 KVB=18.4 VCT=0.00 RGI=2000 CCG=4.3p CPG1=0.6p CCP=5.1p
RE1  7 0  1MEG    ; DUMMY SO NODE 7 HAS 2 CONNECTIONS
E1   7 0  VALUE={V(2,4)/KP*LOG(1+EXP((1/MU+V(3,4)/V(2,4))*KP))} ; E1 BREAKS UP LONG EQUATION FOR G1.
G1   1 4  VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1*ATAN(V(1,4)/KVB)}
G2   2 4  VALUE={(EXP(EX*(LOG((V(2,4)/MU)+V(3,4)))))/KG2}
*G2   2 4  VALUE={PWR(if( V(2,4)/MU+V(3,4) < 0 , V(2,4)/MU+V(3,4), 0 ) ,EX )/KG2}
*G2   2 4  VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG2*(2.5708-ATAN(V(1,3)/KVB))}
RCP  1 4  1G      ; FOR CONVERGENCE    A  - C
C1   3 4  {CCG}   ; CATHODE-GRID 1    C  - G1
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
 
Administrator
Joined 2004
Paid Member
Curious, but from which Russian data-book/sheet did those 6S3P curves come from?

I have several, but the one I referred to specifically in this case is available here:

http://www.mif.pg.gda.pl/homepages/frank/sheets/112/6/6S3PEV.pdf

I do not know the specific origin of this data sheet, most Soviet era data sheets do not list specific vendors. It probably came out of some design bureau in Moscow or St. Petersburg. Russian language data sheets are packed with these tubes, complete with inspection stamp which is both on the tube and the data sheet.. (And the symbol for Reflektor, the only maker I have identified for the EV version)
 
Code:
.SUBCKT 6973  1 2 3 4 ; A G2 G1 C (Pentode)
* RCA data sheet
* library format: LTSpice 14-Nov-2009
+PARAMS: MU=13.58 EX=1.350 KG1=1142.2 KG2=4500 KP=27.70 KVB=18.4 VCT=0.00 RGI=2000 CCG=4.3p CPG1=0.6p CCP=5.1p
RE1  7 0  1MEG    ; DUMMY SO NODE 7 HAS 2 CONNECTIONS
E1   7 0  VALUE={V(2,4)/KP*LOG(1+EXP((1/MU+V(3,4)/V(2,4))*KP))} ; E1 BREAKS UP LONG EQUATION FOR G1.
G1   1 4  VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1*ATAN(V(1,4)/KVB)}
G2   2 4  VALUE={(EXP(EX*(LOG((V(2,4)/MU)+V(3,4)))))/KG2}
*G2   2 4  VALUE={PWR(if( V(2,4)/MU+V(3,4) < 0 , V(2,4)/MU+V(3,4), 0 ) ,EX )/KG2}
*G2   2 4  VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG2*(2.5708-ATAN(V(1,3)/KVB))}
RCP  1 4  1G      ; FOR CONVERGENCE    A  - C
C1   3 4  {CCG}   ; CATHODE-GRID 1    C  - G1
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
Thank you very much cogsncogs, this is a very good tube. :)
 
Ex-Moderator
Joined 2011
4P1L UL Characteristic & SPICE Model

Someone asked for the UL characteristic for 4P1L, here is one with 40% tap:

An externally hosted image should be here but it was not working when we last tested it.


Here is the SPICE model based on the datasheet found here.

Code:
*
* Generic pentode model: 4P1L_AN
* Copyright 2003--2008 by Ayumi Nakabayashi, All rights reserved.
* Version 3.10, Generated on Wed Jan 08 17:33:48 2014
*               Plate
*               | Screen Grid
*               | |  Control Grid
*               | |  |  Cathode
*               | |  |  |
.SUBCKT 4P1L_AN A G2 G1 K
BGG   GG   0 V=V(G1,K)+1
BM1   M1   0 V=(0.020703576*(URAMP(V(G2,K))+1e-10))**-0.32815356
BM2   M2   0 V=(0.8205*(URAMP(V(GG)+URAMP(V(G2,K))/8.67)))**1.8281536
BP    P    0 V=0.0016959897*(URAMP(V(GG)+URAMP(V(G2,K))/10.566728))**1.5
BIK   IK   0 V=U(V(GG))*V(P)+(1-U(V(GG)))*0.00103*V(M1)*V(M2)
BIG   IG   0 V=0.00084799486*URAMP(V(G1,K))**1.5*(URAMP(V(G1,K))/(URAMP(V(A,K))+URAMP(V(G1,K)))*1.2+0.4)
BIK2  IK2  0 V=V(IK,IG)*(1-0.4*(EXP(-URAMP(V(A,K))/URAMP(V(G2,K))*15)-EXP(-15)))
BIG2T IG2T 0 V=V(IK2)*(0.857*(1-URAMP(V(A,K))/(URAMP(V(A,K))+10))**1.5+0.143)
BIK3  IK3  0 V=V(IK2)*(URAMP(V(A,K))+908)/(URAMP(V(G2,K))+908)
BIK4  IK4  0 V=V(IK3)-URAMP(V(IK3)-(0.0010943584*(URAMP(V(A,K))+URAMP(URAMP(V(G2,K))-URAMP(V(A,K))))**1.5))
BIP   IP   0 V=URAMP(V(IK4,IG2T)-URAMP(V(IK4,IG2T)-(0.0010943584*URAMP(V(A,K))**1.5)))
BIAK  A    K I=V(IP)+1e-10*V(A,K)
BIG2  G2   K I=URAMP(V(IK4,IP))
BIGK  G1   K I=V(IG)
* CAPS
CGA   G1  A  0.1p
CGK   G1  K  5.6p
C12   G1  G2 3.7p
CAK   A   K  8.5p
.ENDS
 
Last edited:
Ex-Moderator
Joined 2011
Freshly traced 4P1L with uTracer. Will create new models for triode-mode with starved filaments.
Thanks,
Ale

These are very nice looking curves but not quite the same as the datasheet due to manufacturing tolerance, in any case, for simulation purpose, the difference can be compensated by altering Vg2 a little bit, so the above model can still be used.

An externally hosted image should be here but it was not working when we last tested it.
 
Yes, I tested 10 4P1L and all measured about 18-20% over data sheet specs. This one is 19% I believe. I took care of plotting screen current as generally is not a value available and thought it was good to have to adjust the model.

Those published curves are not the same I have. Where did you get them from?

Does the Ayumi model cater for screen current? How can you adjust it?


Regarding the gm curve, I forgot to increase the polynomial order to 5 at least to get gm curve better adjusted

Thanks
Ale
 
Ex-Moderator
Joined 2011
Those published curves are not the same I have. Where did you get them from?

The datasheet is from here.

Does the Ayumi model cater for screen current? How can you adjust it?

Sorry I was not more clear, you do not need to modify the model itself, but instead make the adjustment by changing the voltage connected to the screen grid in the simulation circuit.