Tag: 4P1L spice model

4P1L with screen as anode

A friend in DIYAudio came up with a great idea of using the 4P1L in a different way for a pre-amp/line stage. Given availability of IT and its gapped current, he suggested connecting the 4P1L differently. Instead of using the anode as the anode element, the screen is used as anode. The 4P1L screen has a maximum current of 10mA and dissipation should be within the 1.5W.

The 4P1L curves in this mode

Let’s look at an initial transfer curve with Uak=100V:

4P1L Screen as Anode transfer

 

 

 

 

 

 

 

 

I wired the 4P1L in the following way to allow tracing with the uTracer:

4P1L screen as anode connectionThe connection is slightly different as the one suggested by Indra. If you are looking to implement filament bias, you will have to rearrange the anode and suppressor grid connection and expect a slight shift on the curves given the change in bias. Filaments are in series here, however is preferred to wire them in parallel when using this valve in filament bias as a smaller filament resistor will be required given there is twice the filament current when filaments are connected in parallel. This will help to keep the output resistance lower as the size of this resistor is smaller (remember it is reflected multiplied by μ+1 times.

Continue reading “4P1L with screen as anode”

4P1L model improved

 Improving the DHT model in A2

After playing for some time with the uTracer, I found that the tracer wasn’t measuring accurately A2 curves. Ronald clearly advised me (as explained on his site) that uTracer wasn’t designed for this purpose although there was a great trick to use the screen driver to generate the A2 curves and also measure grid current. Measuring grid current is key in A2 mode so a better grid current model can be derived to better simulate the non-linear and low impedance behavior of the grid in positive bias.

My incarnation of the uTracer is not neat. I’m using my existing analogue curve tracer. As shown in the pictures below, my current tracer have a plethora of sockets and just adding right jumper cables for anode, cathode, screen and grid connectors will still give me the flexibility I had with my analogue tracer

Additional 3,300uF capacitor across C13 to help A2 traces
My version of the uTracer
uTracer using my analogue tracer sockets 🙂

The process of generating the A2 curves (and SPICE model) starts by plotting the normal curves. The uTracer is great for this. Then you have to overlay the A2 curves in Excel (or whatever tool you prefer) to combine both set of curves.

Continue reading “4P1L model improved”

4P1L triode SPICE model

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 Model Continue reading “4P1L triode SPICE model”

4P1L SPICE model updated

Dmitry Nizh kindly worked out the 4P1L triode SPICE model using his great tool:

4P1L_triode_match

 

Here is Dimtry’s model:

** 4P1L_TRIODE ************************************************************

* Created on Mon Jan 07 07:31:48 PST 2013 using tube.model.finder.PaintKIT
* URL: http://www.bartola.co.uk/valves/valve-curves/4p1l/
*————————————————–
.SUBCKT TRIODE_4P1L_TRIODE 1 2 3 ; P G K ;
+ PARAMS: CCG=8P CGP=7P CCP=9P RGI=2000
+ MU=8.232 EX=1.3719 KG1=851.25 KP=108.0 KVB=528.0 VCT=-1.0 ; Vp_MAX=450.0 Ip_MAX=0.08 Vg_step=5.0
*————————————————–
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
*$