7591 Spice Model ?...Anyone ?... I'm Groveling Over Here !

[valveitude]

Ok, I am seriously needing a model for a 7591. I am barely proficient at LtSpice, and a long ways from being able to do my own models yet. I have tried a couple of tube modeling programs that members here have written…but I stink up the place, and haven’t had any success.

It would be really swell if one of the spice Uber-User’s here could spend a little time and produce one…please…pretty please.

Since the 7591 is back in production, and a lot of vintage gear run ‘em, I am positive that I’m not the only one that could use this model…think of the fame…think of the adoring adulation’s…think of ME!

Did I say please?

Casey

[Robert McLean]

Hello Casey :
Your pleading has touched me to my very heart. I can feel your pain. So since I am in a generous mood today, I decided to work up a model for you.

But I found that none of the spec sheets I could find for 7591 give plate curves. This may explain the lack of published models for 7591. But surely there must be plate curves somewhere for 7591.

I do not have any 7591 personally, so I can't measure the data myself. (which I prefer to do rather than using spec sheets anyway)

You mention that you have tried modeling unsuccessfully, do you mean for 7591 specifically, and if so do you have 7591 data ?

[valveitude]

Heres the Pentode curves.

[valveitude]

Heres the triode connected curves.

[valveitude]

You mention that you have tried modeling unsuccessfully, do you mean for 7591 specifically, and if so do you have 7591 data ?

Unfortunately that was a general statement..never had any luck with the beta programs.

I can't thank you enough for the effort.

Casey

[Robert McLean]

Casey :

Try this model. Its not the greatest fit below 50 volts, but it is not bad for the limited data available. The shape of the plate curves looks a bit funny below 50 volts, but curves I ran in triode mode look pretty good. Use at your own risk, no guarantees and all that stuff.

****
*
* R McLean 9 January 2005
*
* 7591 pentode
* parameter extraction, from data sheets, 9 January 2005
* grid current not modeled
****
*
.SUBCKT 7591 A S G K
+ PARAMS: Ex=1.3215754205161 Kg1=972.600855246932 Kp=97.9392597291279

Kvb=25.0367202802361 Mu=16.7208998295801
+ Exd=2.78742077218546 Kd=159498.449500327 Ks=1.89047582270854

Kg=0.00189539610643784
+ CCG=10.0P CPG1=0.25P CCP=5.0P

Eat at 0 Value={limit(0.636*ATAN(limit(V(A,K),0,2000)/KVB),0,1)} ;

arctangent shaping
Eme me 0 VALUE={PWR(LIMIT(V(A,K),0,2000),EXD)/KD} ; diode line
Egs gs 0 VALUE= {V(S,K)/KP*LOG(1+EXP((1/MU+V(G,K)/V(S,K))*KP))} ;

effective voltage
Egs2 gs2 0 VALUE={(PWR(V(gs),EX)+PWRS(V(gs),EX))/(KG1*0.636)} ; total

space current
G1 A K VALUE={LIMIT(V(gs2)*V(at),0,V(me))} ; plate current
Escrn sc 0 VALUE={KS*V(gs2)*(1.1-V(at))} ; reverse arctan shaping for

screen current
G2 S K VALUE={Limit(V(sc),0,10)*LIMIT(V(S,K),0,10)/10} ; screen

current
* no grid current data available so comment out the grid current line
*G3 G K VALUE={PWR(LIMIT(V(G,K)+1,0,1E6),1.5)*(1.25-V(at))*KG} ;

grid current
C1 G K {CCG} ; CATHODE-GRID 1
C2 A G {CPG1} ; GRID 1-PLATE
C3 A K {CCP} ; CATHODE-PLATE
.ENDS 7591

[Robert McLean]

After I posted my last message I saw that the lines were not wrapping properly, ie my cut and paste did not work quite right. You could fix it manually, but thats a pain, so here is the model uploaded as a text file.

[valveitude]

THANK YOU MR. McLEAN !!!

I will model my Fisher's output stage this evening, and report back.

Its not the greatest fit below 50 volts, but it is not bad for the limited data available.

Hey, if your thirsty enough, it doesn't mater if the water is a little cloudy I'm sure it's good enough to show the relative performance differences of different splitter/driver schemes I'm considering.

You may want to check the date on your file ...glad I'm not the only one writing '05 on my checks.

Is it ok to share this model, as long as I leave your info on it ? I suspect others would be interested in it.

Thanx again Robert...you 'da man!!

Casey

[Robert McLean]

You may want to check the date on your file ...glad I'm not the only one writing '05 on my checks

Hey, its only the 10'th day of the year. Wait till March and see if I am still doing it

Is it ok to share this model, as long as I leave your info on it ?

Absolutely, spread it around, the more the merrier.

[valveitude]

Hey, its only the 10'th day of the year. Wait till March and see if I am still doing it

My personal "best" was May

Just a quick note to say that I successfully simulated my Fisher 800C's power amp using this model in LtSpice...thanx again Robert, and to everyone else this model works .

Casey