Long Tail Phase Inverter 12at7

[Sammaypipes]

I realize that vacuum tube amps are a lesser technical form of electronic appliance.  However, I am attempting to simulate one nonetheless.  

I have been trying to simulate an amp that I have built in order to simulate different mods but every time I have encountered a Convergence Error.  I have narrowed down the error to happening only when the the tube models involved in the Long Tail Phase Inverter are connected to the circuit.  Clearly, this circuit works, as I have built it, and guitar amps have been using this type of phase inverter for over 50 years in amps like the 5F6A Bassman and the AB763 Deluxe Reverb.  Has anyone else managed to make a push/pull tube amp work with a standard Long Tail Phase Inverter in multisim?  

[gmack]

I have using a 12AU7 in my McIntosh MA230 simulator (see attached schematic).  Make sure you don't "overdrive" the NI tube models though!

[Sammaypipes]

I don't yet have a lot of experience with Multisim's tube models but how do they compare to their real life counterparts?  My circuit is giving me convergence errors without even applying a signal voltage to the circuit- just B+ and filament voltage.

[gmack]

Im' still working on that issue - see my posts (I'm "jmack") at http://www.diyaudio.com/forums/tubes-valves/243950-vacuum-tube-spice-models-73.html#post4211642.

[gmack]

Since the 12AT7 was omitted from the Multisim 13 Database, I suspect that you're using one from an older version.  The 12AT7 model (and most-all of the others?) in the Multisim 10 Database are not good models (the left hand side of the Triode Plate Characteristics parabola isn't suppressed).  You can easily check them by using "DC sweep" Analysis with the plate voltage as "Source 1" and the gate voltage as "Source 2" with plate current as the output.  You can download datasheets for comparison from http://www.drtube.com/en/library/tube-datasheets (as well as amplifier schematics).  For tube ("Valve") SPICE models (and another source of datasheets and schematics) see http://www.duncanamps.com/spice.html.  Multisim 13 Power Pro uses the Dave Cigna models.

[lucaso3]

Hi Sammaypipes,

I am not very sure which errors you have, but you probably might find these links useful:

http://digital.ni.com/public.nsf/allkb/A65253BD02F585CD86257A6B0049945D

https://decibel.ni.com/content/groups/circuit/blog/2012/03/12/ni-multisim-spice-simulation-and-the-c...

http://digital.ni.com/public.nsf/allkb/4B99B2CD6C0C3B6A86257205005D58E0

http://forums.ni.com/t5/Circuit-Design-Suite/Unable-to-solve-convergence-error/td-p/1488044

I really hope this information may clear help you solve the convergence errors.

Luis C.

National Instruments

[gmack]

You kinda got me curious so I generated some Plate Characteristics Graphs for several the 12AT7 SPICE Models.  It looks like the Koren model most closely matches the data sheet.   See the attachment.

[Sammaypipes]

Thanks for all your interest you guys. Yes I have an older version 12. It seems like whether I use 12at7 or 12ax7 they all have the convergence error. I'm not an engineer YET! Just a student and so I am not entirely amazing on the simulator yet. I'll take a look at the links you sent and see if I can get it to work