Norman Koren        SPICE/PSpice tube model package and instructions

updated August 28, 2001
This page contains instructions for the files and models that accompany Norman Koren's articles on SPICE and preamplifier design, most notably Improved Vacuum Tube Models for SPICE Simulations and SPICE and the art of preamplifier design. The models can be downloaded as a compressed file which must be "unzipped" with Pkunzip, Winzip or a similar program by shift-clicking here on Tubemods.zip.

These models are available as shareware. All the usual legal disclaimers apply to these models. They were developed with the best efforts of the author, who bears no legal liability for their use or misuse.

The parameters in my tube models are based on published data sheets, and are far from perfect for all cases. Tubes vary from unit-to-unit and batch-to-batch. My chief sources of tube data are Duncan's Amp Pages and Frank's Electron tube Pages.

Several files come with each PSpice model. The .dat files (complete results of a PSpice simulation used as input to Probe) are not included because they're too large and not readable.
 

PSpice file extension Description
.SCH Schematics diagram file.
.CIR Control file generated by Schematics. ASCII.
.NET Netlist (circuit description) generated by Schematics. ASCII.
.ALS Alias file generated by Schematics. Needed for PSpice simulation.
.PRB Control file for Probe plots. Contains settings from last run, scaling, etc.
.DAT Complete output file generated by PSpice; input to Probe. Not readable; very large, hence not included in shareware package.
.OUT Readable ASCII output file from PSpice simulation. Contains dc levels, etc.
August 28, 2001:  Some of these files are out of date. I'll be updating and purging them in the next few weeks. The .sch files for individual tubes are older, but should work OK.
File name Description
Pent_P.sch ... Schematic for calculating plate characteristic curves from pentodes in Pentode mode. Uses 6550; other tubes may be substituted.
Pent_UL.sch ... Schematic for calculating plate characteristic curves from pentodes in Ultra-Linear mode. Uses 6550; other tubes may be substituted.
Pent_TR.sch ... Schematic for calculating plate characteristic curves from pentodes in Triode mode. Uses 6550; other tubes may be substituted.
TRIOTEST.sch Schematic for calculating generic triode plate curves. Uses 12AU7; other tubes may be substituted.
12AX7TST.sch Schematic for calculating 12AX7 plate curves (used by Pspice Schematics program).
12AU7TST.sch Schematic for calculating 12AU7 plate curves.
EL34PTST.sch Schematic for calculating EL34 plate curves (pentode mode).
EL34TTST.sch Schematic for calculating EL34 plate curves (triode mode).
EL34UTST.sch Schematic for calculating EL34 plate curves (ultra-linear mode).
errata.txt Errata for GA Tube models article with additional models.
Pasorgtc.sch ... Original Dynaco PAS with tone controls.
Paspursp.sch ... Spiced PAS, purist version (without tone controls).
Pasphon.sch Spiced PAS phono preamp.
Paspurln.sch Spiced PAS line stage- purist mod.
Pentode.cir SPICE file for calculating pentode plate curves. Old.
Lochero.sch ... "Local Hero" amplifier (modified Dynaco Mark 3) from Feedback and Fidelity, Part 2.
psreadme.txt Old instructions-- kept for historical interest.
trio300B.sch Schematic for calculating 300B curves from Western Electric data reprinted in The Parts Connection Catalog & Resource Guide.
Triode.cir SPICE file for calculating triode plate curves. Old.
Tube.lib Tube model library.
Tube.slb Tube symbol library
Tube1.lib and Tube1.slb Additional tube model and symbol libraries : I moved some devices that I'm not currently using into these files because the evaluation version of PSpice limits user-created libraries to 20 models.
PAS94.TXT Excerpts from the 1994 PAS modification article.  Should help with some of the construction details.  Turn on word wrap to view if you use Notepad.

Files in the shareware package

Several commercial versions of SPICE run on personal computers, most notably PSpice from Orcad, 888-671-9500. The downloadable Pspice evaluation package has limited capabilities by standards of solid-state circuit design, but it can be amazingly useful in simulating vacuum tube amplifiers, which tend to have fewer components. All examples in this article can be run on the MicroSim Pspice evaluation package. Other well-known SPICE implementations include Electronics Workbench, 800-263-5552, and ICAP/4, from Intusoft, P.O Box 710 San Pedro, CA 90733-0710; 310-833-0710. Duncan Munro's list of SPICE vendors may contain some hidden treasures. WinSpice is a free Spice3F4 Port for Windows 95, 98, 2000 & NT. Very intriguing. It will simulate much larger circuits than evaluation PSpice.

The simulations in the accompanying files can be run on the PSpice evaluation package, which consists of Schematics for entering circuits, PSpice for simulating them, Probe for viewing the simulation results, a set of documentation and tutorials.

I'm still using Pspice version 6.3 because versions 7+ limit the total number of parts more strictly (to 50). In the newer versions, files that contain both the phono preamplifier and line amplifier (such as paspursp.sch) may need to be separated into two separate files. For those of you who run into problems with Paspursp.sch, I have included Pasphon.sch (phono only) and Paspurln.sch (line amp only).

Installing the tube and symbol libraries



After you've installed PSpice on your computer you must install or create the tube models.  Although PSpice is up to level 9.1 as I write this, I use version 6.3 for this example because I'm familiar with it and because you can also get away with a few more parts than newer versions allow. I assume you've downloaded my models. You'll need to install two files: the tube symbols (TUBE.SLB) and SPICE models (TUBE.LIB). Both are installed from the Schematics program.

Installing the symbol library (TUBE.SLB)--  From the Schematics screen, click Options, Editor Configuration..., Library Settings. The screen on the right appears. Enter the foll pathname of the file containing the schematics symbols, except for the extension, in the Library Name: window, C:\NORMK\AUDIO\TubeShar\TUBE in the example. Check the box to the left of Symbol to get the .slb file extension. Click OK, OK.

Window for entering .slb symbol library

 

Installing the SPICE model library (TUBE.LIB)-- From the Schematics Screen, click Analysis, Library and Include Files... The screen on the right appears. Enter the full pathname of the SPICE model file (including extension) in the File Name: window, C:\NORMK\AUDIO\TubeShar\TUBE.LIB in the example. Click Add Library*, OK, OK.

PSpice should be ready to run with tubes!

Creating your own models


The technique for linking drawings to models is quite complex, and the PSpice tutorial must be studied to grasp it. It would be wise to look it over before continuing! The following steps will bring up a good example that can be adapted for tube models. From Schematics, click on File, Edit Library to get into the Parts Library editor. Click on File, Open..., eval.slb to open a library file that contains some parts useful as examples. (Be patient: Your screen will still be blank at this point.) Click on Part, Get..., IRF9410 to load the drawing for a P-channel mosfet. (Choose another part if you desire, but this MOSFET is as close as you can get to a tube in this library.) Click on Part, Attributes... to see the statements that define this part. For the IRF9410, they are

template=M^@refdes %d %g %s %s @MODEL
refdes=M?

PART=IRF9140
MODEL=IRF9140

Template links the part to the model library: With appropriate substitutions, for example, IRF9140 for @MODEL, it appears in the netlist. A number on the schematic diagram replaces ? in refdes. To alter an attribute, click on it in the box on the right and edit it in the boxes on the upper left. The attributes of the 12AX7 that link it to its subcircuit in TUBE.LIB are:
template=X^@REFDES %P %G %C @MODEL
refdes=TU?
PART=12AX7
MODEL=12AX7
To create a new library file, click on File, New, then File, Save as..., tube.slb (or a full path name of your choice). To insert a part into the new library file, draw it following instructions in the tutorial or modify an existing part (such as the IRF9410), then save it by clicking Part, Save to Library... Either type the library file name or use the usual Windows navigation techniques to locate it. Good luck and please do the tutorial.

Parts are entered into PSpice Schematics drawings by clicking on the little box with the "and" gate. You can enter "R", "L", "C", "BUBBLE", etc. for common parts, or click on Browse... to examine a library of parts. I recommend using the rubberband option, which can be set by clicking Options, Display Options..., Rubberband. Named nodes (1G, 1P, etc.), which are created by double-clicking on lines and entering a name, are required for voltages to be examined in Probe. Input files to Schematics have the three character extension .SCH. Clicking Analysis, Create Netlist creates files with extensions .CIR (the control file), .NET (the netlist), and .ALS (an alias file which speeds up analysis) which are used as inputs to Pspice. The .CIR and .NET files contain ASCII text in SPICE format, as described in Paul Tuinenga's excellent text10. Clicking Analysis, Simulate creates the netlist, runs Pspice, and loads Probe to display results. Press the Insert key to select a voltage or current for Probe display. You can use "VDB" or "VP" to display a voltage in dB or its phase in degrees. There are many more possibilities for controlling the display.

Obtaining plate curves

Figures 3 and 4 on the previous page are schematics diagrams for generating triode and pentode characteristic curves. Their netlists are shown in Appendices A1 and A2. Each of these circuits requires that you perform a few added steps to generate the characteristic curves. We will use the pentode (Fig. 4) as an example.

To step the grid voltage, click on Analysis, Setup..., Parametric... Set Swept Var. Type to Voltage Source, Sweep Type to Linear, Name: to VG1, Start Value to 0, End Value: to -75 (or as appropriate), and Increment: to -15 (or as appropriate), then click OK. You may set the plate voltage sweep while the Analysis Setup... box is still open. Click DC Sweep... Set Swept Var. Type to Voltage Source, Sweep Type to Linear, Name: to VP, Start Value to 0, End Value: to 600 (or as appropriate), and Increment: to 5 (or as appropriate), then click OK. The DC Sweep... and Parametric boxes should contain check marks. Finally, click Close. All voltage sources except VG2NOM are set to DC=0 in the schematic diagram. (Attributes can be viewed and changed by double-clicking on the symbol.) Grid and plate voltages are controlled by the DC Sweep... and Parametric... settings.

VG2NOM is the nominal screen grid voltage. It is 300V in Figure 5 (pentode mode) and 450V in Figure 7 (ultra-linear (UL) mode). (It has no meaning in triode mode, where screen grid voltage equals the plate voltage). E2 is an EVAL voltage-controlled voltage source that controls how the screen grid voltage tracks the plate voltage. For Ultra-Linear mode it is set to V(%IN+, %IN-)*.4+V(1P)*.6 . For pentode mode it is V(%IN+, %IN-). For triode mode it is V(1P). VP is set to zero: -I(VP) is the correct polarity for plate current plotted by Probe. When you have completed entering the schematic, click Analysis, Simulate. This will create a netlist, run PSpice, and then run Probe to display the results. Error messages can appear at any one of several stages of this process. They are unavoidable when you start out. Don't get frustrated. This is where real learning happens.


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