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Thanks to Helmut for the hints to making model-libs and coverting plain Spice-
Ascii text.
I encounterd problems with the model of the vacuum tube 12AX7 below. Apart from
being rather far from reality, this model seems to produce convergence problems.
LTspice throws an abort "time intervall too small" whatever time invall I put in
the .tran and also controlPanel. The shown waveform heavily varies.
Winspice concludes computing.

I earlier decided to develop Musician's Ampifiers, which imitate a tube-
Amplifier together with it's output transformer using analog and switched
circuits - not computing it, this had been done already. Guitarists love there
sound, I do so too. I intend a switched output stage and supply to save power
consumption and weight. There main features are:

- huge dynamic range
- nonlinearity depending on the signal's time domain
- compression effects (and filtering) highly depending on the signal
- some strange storage effects at medium and high levels

I made lots of step-/puls-responses of this kind of amplifiers to get there
behaviour. I is quit more than just nonlinearity.
Are there special devices from LT for this purpose ?
thanks, Arnold



* ECC83_2.cir

V1 1 0 DC 0 AC 1 PWL(0 0 1m 0 6m -5 16m 5 21m 0)

R1 1 0 100K
R3 3 0 2.2K
R4 4 100 150K
X1 4 1 3 NH12AX7

VP 100 0 DC 250

.TRAN 100u 50m 0 100u
.PRINT TRAN V(4)


* GENERIC: 12AX7 / ECC83
* MODEL: NH12AX7
* NOTES:
*--------------------------------------------------------------------------
* Connections: Anode
* | Grid
* | | Cathode
* | | |
.SUBCKT NH12AX7 A G K
*
* ANODE MODEL
BLIM LI 0 V=(URAMP(V(A)-V(K))^ 1.5 )* 1.6e-5
BGG GG 0 V=V(G)-V(K)--0.53056
BRP1 RP1 0 V=URAMP(-V(GG)* 0.076498 )
BRP2 RP2 0 V=V(RP1)-URAMP(V(RP1)-0.999)
BRPF RP 0 V=(1-V(RP2)^ 1 )+URAMP(V(GG))* 0.18
BGR GR 0 V=URAMP(V(GG))-URAMP(-(V(GG)*(1+V(GG)*-0.013621 )))
BEM EM 0 V=URAMP(V(A)-V(K)+V(GR)* 87.302 )
BEP EP 0 V=(V(EM)^ 1.5 )*V(RP)* 1.11e-6
BEL1 EL1 0 V=URAMP(V(EP))
BEL EL 0 V=V(EL1)-URAMP(V(EL1)-V(LI))
BLD LD 0 V=URAMP(V(EP)-V(LI))
BAK A K I=V(EL)
*
* GRID MODEL
BGF GF 0 V=(URAMP(V(G)-V(K)--0.2 )^1.5)* 1e-5
BG G K I=V(GF)+V(LD)
*
* CAPS
CAK A K 0.7P
CGK G K 2.4P
CGA G A 3.9P
*
.ENDS



.END

--- In LTspice@..., Arnold Esper <arnold.esper@n...>
wrote:

Thanks to Helmut for the hints to making model-libs and coverting

plain Spice-

Ascii text.
I encounterd problems with the model of the vacuum tube 12AX7

below. Apart from

being rather far from reality, this model seems to produce
convergence problems.

Hello Arnold,
I tried your example also without luck. The next step you normally
would do is testing the transfer function I_A(Ugk).
Ok, I did it for you. The gain was a factor of 1000 to less. I
remembered something with '^' and '**' for the power operator. After
some trial and error I came to the conclusion that LTSPICE has been
guilty for the wrong result.

Hello Mike,
why doesn't LTSPICE follow SPICE3 syntax with the '^' power operator.
LTSPICE only accepts '**' for the power operator. If I tried '^' for
the power, the result seems to be always 1.


Now Arnold, it is clear would you have to do. Replace any '^'
with '**' in all your models. I tested it already with the **
operator and it is then ok.

Example:

BLIM LI 0 V=(URAMP(V(A)-V(K))^1.5 )* 1.6e-5

BLIM LI 0 V=(URAMP(V(A)-V(K))**1.5 )* 1.6e-5

Best Regards
Helmut