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Old 26th January 2012, 07:02 AM   #11
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Hey Kevin,
I use Stephie´s GM70 model and it seems to work OK. Have you compared the two by simulating the U/I-curves in LTSpice?
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Old 26th January 2012, 01:54 PM   #12
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R1 is Kevin, R6 is Bench. I haven´t checked against datasheets. Ug 0 to -100V in 10V interval.
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Old 26th January 2012, 06:08 PM   #13
kevinkr is offline kevinkr  United States
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Hi Lars,
I haven't compared the two, and in fact did not know of SB's GM70 model's existence until you mentioned it.

Interesting that the curves appear so different, and I have no clue as to which is more accurate, but given Stephie's level of experience possibly her's is the more accurate model. I used paint_kit.jar to create my model and got a very good curve match the second attempt. Wondering if this is a reflection of the complexity of the model, a goof on my part or both..

I have noticed a number of differing curves for the GM70 on the web that do not seem to match well. I no longer remember where I got mine, but the predictions from those curves match actual measured performance well. (I can probably locate those curves at some point though)

I have not gotten very far in correlating the actual measured electrical performance of the GM70 in my amp with the spice model predictions, but there didn't seem to be anything that immediately caused concern. The predicted OP seems to match up reasonably well with what I have measured.
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Old 26th January 2012, 06:17 PM   #14
kevinkr is offline kevinkr  United States
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Hi Lars,
As a reality check Ug across six different GM70 samples at 980V and 120mA ranged from about -75V to -85V, at least 4 of these devices were almost exactly -80V.

Next time I am working on the amplifiers I will take some more careful measurements just to verify/refute/refine these values.
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Old 27th January 2012, 07:32 AM   #15
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Remove .txt and try the two models. Check curves by clicking R1 resp. R6. Seems like none of them neither the datasheets are like your IRL tests.

Why not make curves from your reality test data and a Spicemodel according to that? Seems like the tubes measure quite consistent.
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Last edited by revintage; 27th January 2012 at 07:42 AM.
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Old 29th August 2012, 07:21 AM   #16
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Quote:
Originally Posted by payloadde View Post
Jaz,
I can't find parameter <KC> in Koren's model. Can you explain ?

******************
.SUBCKT EF86 1 2 3 4 ; A G2 G1 C (Pentode)
* Philips data sheet AKA 6CF8 and 6267 Z729 EF806
* library format: LTSpice 02-Jun-2008
X1 1 2 3 4 PENTODE1 MU=34.90 EX=1.350 KG1=2648.1 KG2=4500 KP=222.06 KVB=4.7 VCT=0.00 RGI=2000 CCG=4.3p CPG1=0.6p CCP=5.1p ;
.ENDS EF86
So sorry, did not catch your post until now, it's a typo, KC should read KG2.

Jaz
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Old 29th August 2012, 07:57 AM   #17
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I noticed that the EL34-model from Koren which I have mostly used
is not very accurate. Ig2 is minimal and much lower than in real tube.
For example, with 250 V Ua/Ug2, the screen current is about 2.2 mA, but in Mullard specs it is some 15 mA.
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Old 29th August 2012, 09:54 PM   #18
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Quote:
Originally Posted by artosalo View Post
I noticed that the EL34-model from Koren which I have mostly used
is not very accurate. Ig2 is minimal and much lower than in real tube.
For example, with 250 V Ua/Ug2, the screen current is about 2.2 mA, but in Mullard specs it is some 15 mA.
I think many of us have discovered that the Koren pentode model does not work as well as his triode model, we have to tweak the parameters manually to get them to work sometimes... The best model I can find for the EL34 is from Excem, but it is a proprietary model, so must be used as is - and is very hard to adapt for other tubes...

Here is the screen current from the Excem model:
Click the image to open in full size.

Jaz
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Old 30th August 2012, 09:19 PM   #19
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Does anyone have Spice model for soviet 6F12P pentode side or 6J53P ?
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Old 31st August 2012, 06:35 AM   #20
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.SUBCKT 6F12PP 1 2 3 4 ; P G1 C G2 (Pentode) 28-Feb-2008
+ PARAMS: MU= 71.45 EX= 1.350 KG1= 260.8 KP=7396.95 KC= 4000
+ KVB= 17.9 VCT= 0.00 RGI= 4500k
+ CCG=6.6P CPG1=0.02P CCP=1.9P
RE1 7 0 1G
RE2 8 4 1G
E1 7 0 VALUE={V(2,4)/KP*LOG(1+EXP((1/MU+V(3,4)/V(2,4))*KP))}
G1 1 4 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KG1*1.57*TANH(2*V(1,4)/(KVB*3.14159))}
G2 8 4 VALUE={(PWR(V(7),EX)+PWRS(V(7),EX))/KC*(2.57-1.57*TANH(2*V(1,4)/(KVB*3.14159)))}
E2 8 2 VALUE={0}
RCP 1 4 1G ; FOR CONVERGENCE
C1 3 4 {CCG} ; CATHODE-GRID 1
C2 1 3 {CPG1} ; GRID 1-PLATE
C3 1 4 {CCP} ; CATHODE-PLATE
R1 3 5 {RGI} ; FOR GRID CURRENT
D3 5 4 DX ; FOR GRID CURRENT
.MODEL DX D(IS=1N RS=1 CJO=10PF TT=1N)
.ENDS
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