All about electronic valves and hi-fi
This build became one of the quickest and eventually the most painful from all, perhaps not really. However, it was very challenging in the end. I will tell you why in more detail. Yet, it has been a fantastic learning experience.
After some proper time tracing the curves, here are a set of Russian high-frequency pentodes in triode-mode for comparison. I was looking at closer ones to D3a and these are the ones I had at hand and wanted to include in the tests:
| 6Z5P | 6Z9P | 6Z11P | 6Z49P-D | 6Z51P | 6P15P | 6E5P | 6E6P-E | D3a | |
| Vf [V] | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 | 6.3 |
| If [ma] | 450 | 300 | 440 | 300 | 300 | 760 | 600 | 610 | 315 |
| Pa [W] | 4 | 3.75 | 6 | 3.4 | 3.5 | 13.5 | 10.6 | 8.8 | 4.5 |
| Gm [ma/V] | 7 | 35 | 33 | 17.75 | 29 | 16 | 32 | 25 | 34 |
| μ | 44 | 36 | 40 | 44.3 | 79.5 | 22 | 30 | 34 | 68 |
| Ra [Ω] | 6K2 | 1k | 1K2 | 2K5 | 2K7 | 1K6 | 960 | 1K3 | 2K |
| Ia [ma] | 16 | 29 | 40 | 15.7 | 23 | 52 | 50 | 30 | 22 |
| Va [V] | 252 | 125 | 150 | 200 | 150 | 250 | 200 | 200 | 200 |
Well, as you can see in the table above, the 6e5p and 6e6p-e (both tetrodes) were included in the list. Some interesting points to highlight:
Using my C3g and D3a triode curves, I developed the following SPICE models:
** D3A TRIODE ************************************************************
* Created on Sat Jan 12 09:17:53 GMT 2013 using tube.model.finder.PaintKIT
* model URL: http://www.bartola.co.uk/valves/valve-curves/d3a-triode/
* Created by Ale Moglia valves@bartola.co.uk
*--------------------------------------------------
.SUBCKT TRIODE_D3A 1 2 3 ; P G K ;
+ PARAMS: CCG=6.7P CGP=3.3P CCP=1P RGI=2000
+ MU=72.1 EX=1.456 KG1=65.625 KP=534.0 KVB=300.0 VCT=0.0557 ; Vp_MAX=500.0 Ip_MAX=0.07 Vg_step=0.5
*--------------------------------------------------
E1 7 0 VALUE={V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(VCT+V(2,3))/SQRT(KVB+V(1,3)*V(1,3)))))}
RE1 7 0 1G
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1}
RCP 1 3 1G ; TO AVOID FLOATING NODES
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
*$
** C3G TRIODE ************************************************************
* Created on Sat Jan 12 09:40:08 GMT 2013 using tube.model.finder.PaintKIT
* model URL: http://www.bartola.co.uk/valves/valve-curves/c3g-pentodetriode/
* Created by Ale Moglia valves@bartola.co.uk
*--------------------------------------------------
.SUBCKT TRIODE_C3G 1 2 3 ; P G K ;
+ PARAMS: CCG=7P CGP=2.7P CCP=6P RGI=2000
+ MU=50.4 EX=1.428 KG1=199.6875 KP=426.0 KVB=204.0 VCT=0.5760 ; Vp_MAX=500.0 Ip_MAX=0.07 Vg_step=1.0
*--------------------------------------------------
E1 7 0 VALUE={V(1,3)/KP*LOG(1+EXP(KP*(1/MU+(VCT+V(2,3))/SQRT(KVB+V(1,3)*V(1,3)))))}
RE1 7 0 1G
G1 1 3 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1}
RCP 1 3 1G ; TO AVOID FLOATING NODES
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