Tubes Model

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https://gist.github.com/chanmix51/6947361
12.10.2013 · * Modeling Of Tubes Employing Genetic Algorithms * * Models contain 1G resistors from all nodes to earth in order to avoid * floating nodes. Triode and tetrode/pentode models contain a diode for * simulating grid current. * * Non-commercial use is permitted, but at your own risk... This model …
https://cbp.tnw.utwente.nl/PolymeerDictaat/node62.html
It is clear from the above picture that the reptative motion will determine the long time motion of the chain. The main concept of the model is the primitive …
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www.normankoren.com/Audio/Tubemodspice_article.html
20.03.2003 · Scott Reynolds 1 and Marshall Leach 2 model vacuum tubes as voltage-controlled current sources whose output …
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Which is the main concept of the tube model?
Which is the main concept of the tube model?
The chain thus creates a new piece of tube and at the same time destroys part of the tube on the other side. This kind of motion is called reptation . It is clear from the above picture that the reptative motion will determine the long time motion of the chain. The main concept of the model is the primitive chain.
cbp.tnw.utwente.nl/PolymeerDictaat/node6…
What kind of models are used for vacuum tubes?
What kind of models are used for vacuum tubes?
* Modeling Of Tubes Employing Genetic Algorithms * Models contain 1G resistors from all nodes to earth in order to avoid * floating nodes. Triode and tetrode/pentode models contain a diode for
How are vacuum tubes modeled in motega software?
How are vacuum tubes modeled in motega software?
* Model generated by Motega software: * Modeling Of Tubes Employing Genetic Algorithms * Models contain 1G resistors from all nodes to earth in order to avoid * floating nodes. Triode and tetrode/pentode models contain a diode for
Which is the best program for finding tube model parameters?
Which is the best program for finding tube model parameters?
James E. Lanier's PSPICE Triode Calculatoris a promising program for finding tube model parameters. It's still under development; he plans to expand it to include tetrodes and pentodes. LTspicecan apparently be used for these models.
www.normankoren.com/Audio/Tubemodspic…
https://www.cgtrader.com/3d-models/a-tube
8 A tube 3D models available for download in any file format, including FBX, OBJ, MAX, 3DS, C4D.
tdsl.duncanamps.com/dcigna/tubes/spice
Spice Models of Vacuum Tubes. Here are models of a few popular audio tubes that have been generously donated by others*. (If you have any working models that you would like to add, please let me know.) general model for the heater of indirectly heated tubes …
https://en.m.wikipedia.org/wiki/Marshall_1959
They were equipped with four KT66 tubes, but models made after 1967 had four EL34 tubes instead; it had three ECC83 tubes in the pre-amplification stage. A model with tremolo, the …
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Replace your old fluorescent tubes with LED tubes in a fixture with an electronic ballast. In this instance you're fixture does …
Александровск-Сахалинский, Сахалинская область
Александровск-Сахалинский, Сахалинская область
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Much of the material in here originally appeared in Glass Audio, Vol. 8, No. 5, 1996, p. 18.

As my principal hobby interest is now photography and I work crazy long hours at Imatest, I won't have much time to update this article or answer difficult questions.

James E. Lanier's PSPICE Triode Calculator is a promising program for finding tube model parameters. It's still under development; he plans to expand it to include tetrodes and pentodes.
LTspice can apparently be used for these models.
SPICE, an electronic circuit simulation program originally developed at the University of California at Berkeley, has found wide acceptance in the electronics and semiconductor industries. It can perform highly accurate time and frequency domain analysis of complex analog and digital circuits (including harmonic and IM distortion). Several commercial versions of SPICE run on personal computers, most notably PSpice from OrCAD. The downloadable PSspice student version (version 9.1 at last look) 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. It was used for all examples in this article. It's hard to find on the OrCAD website. I had to go to the CadencePCB home page and click on All Downloads. 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.
SPICE contains built-in models for passive devices (resistors, capacitors, inductors, etc.) and for most active semiconductor devices (bipolar transistors, FETs, Op Amps, etc.), but none for vacuum tubes. SPICE models and can be downloaded from manufacturer's Websites.
IP = (2/kG1p)(EG+EG2 /�)3/2 arctan(EP /kVB )     for   EG+EG2 /� >= 0
= 0    otherwise.
The screen grid current equation for pentodes is
IG2 = (EG+EG2 /�)3/2/kG2    for   EG+EG2 /� >= 0
= 0    otherwise.

Figure 1. 12AX7 plate curve from the old model.
The difficulty with equations (1) and (2) is that they assume that the grid has perfect control over the plate current, i.e., that there is no leakage current. The real world is, alas, not so kind, and these equations give a poor estimate of plate current for large positive plate voltage and large negative grid voltage,5 region (A) in Figure 1, above. Compare this with region (A) in Figure 2, below, which is derived from the new model but matches published curves4 extremely well.
The modeling error would not be serious if tubes did not operate in the region of greatest error. Unfortunately they do, as illustrated in Figure 1 by a typical load line for a 12AX7 with a 350V plate supply and a 150kW plate resistor. The load line crosses region (A), and operation may extend into this region for large signals. This problem is exacerbated in class AB push-pull amplifiers, where the operation of each tube traverses the region of worst error as it moves from conduction to cutoff and back. An accurate estimate of distortion in push-pull amplifiers is impossible without an improved model.
The new plate current equation for triodes is
E1 = (EP /kP) log(1 + exp(kP(1/� + EG /sqrt(kVB + EP2))))
IP = (E1X/kG1)(1 + sgn(E1))
E1 = (EG2 /kP) log(1 + exp(kP (1/�+EG /EG2)))
IP = (E1X/kG1)(1 + sgn(E1)) arctan(EP /kVB)

Figure 2. 12AX7 plate curve from the new model.
If you plan to modify or add tube models you'll need to know a bit about the SPICE language. Appendix A has listings of several SPICE files. The first line of a SPICE file contains a title. Data on this line is ignored. The last line consists of the .END statement. Netlist data lines have the general format,
I strongly recommend the excellent textbook by Paul W. Tuinenga,10 "SPICE, A Guide to Circuit Simulation & Analysis using PSpice." It contains detailed descriptions SPICE commands and models, including how to perform frequency-domain analysis (.AC), time-domain analysis (.TRAN) and Fourier analysis (.FOUR), which produces a detailed harmonic distortion analysis. In the PSpice Schematics program these instructions are generated by clicking on Analysis, Setup..., then working with the appropriate boxes.
To perform a SPICE simulation with the MicroSim evaluation package, run the Schematics program, then click on File, Open... to open a Schematics data file using the usual Windows navigation techniques. (You can also create a new schematic.) We'll call it filename.SCH in this example. You may edit and save it if you wish. To perform the PSpice simulation, click on Analysis, Simulate. This creates two SPICE language files: filename.CIR containing simulation instructions and filename.NET containing the netlist. These files are then read into the PSpice simulator, which writes text results (voltages, currents, etc.) to filename.OUT and graphics data to filename.DAT for display with Probe, which is run automatically if you have the .PROBE statement in the data file. Probe displays time and/or frequency-domain plots of voltages at selected nodes or currents through selected components. The format of the display is quite versatile. If V(n) is the voltage at node n, VDB(n) is the voltage in dB and VP(n) is the phase. Current display is similarly flexible.
To use the Schematics program I had to create symbols for tubes: a difficult task you can avoid by downloading the models and following the instructions in Appendix B for loading the symbol and SPICE model libraries into PSpice.
The trial and error procedure for finding tube parmaters is tedious. My Matlab program for determing them is now available on Finding SPICE tube model parameters. Two other people have reletant work.
Teodoro Marinucci has written an optimization program in Excel. His website covering tube theory and modeling is mirrored on two URL's, http://web.tiscali.it/teodorom/ and http://digilander.iol.it/teodorom/. Alas, they're in Italian. I don't think his program is online yet, but it's very appealing because almost everybody has Excel. You can encourage him by sending him an e-mail. You can get a crude but readable translation by searching for "Valvole e Matematica" in http://www.google.com, then clicking on [Translate this page] next to his article. Amazing.
Mithat F. Konar's article Vacuum Tube Parameter Identification Using Computer Methods describes a technique that uses the Matlab Optimization Toolbox.
The parameters in Table 1 can be found by a methodical trial and error procedure. To use this procedure, the programs in Appendix A1 through A3 must be employed. Listings A1 and A2 produce plate characteristic curves for triodes and pentodes, respectively. Listing A3 is a portion of the tube library referenced by the .LIB statement in listings A1 and A2. Tubes are modeled as subcircuits, starting with .SUBCKT and ending with .ENDS. .SUBCKT is followed by the model name and then the element node names. We have chosen the order the element nodes to be plate, control grid, cathode, and (in pentodes) screen grid.
To find the parameter values for a new tube, it is best to start with values for a similar existing tube, except for amplification factor MU (�), which is generally close to the manufacturer's specification. MU is (minus) the change of plate voltage for a given change of grid voltage at constant plate current. This is illustrated by line segment BC in Figure 2, which is a good choice for determining MU because it is located in a region of tube operation far from region (A), where effective MU is reduced. In this case, plate voltage increases by 100V when grid voltage is decreased by 1V while plate current remains constant at 1.9 mA, resulting in MU = 100.
To determine EX and KG1 (X and kG1), run the appropriate plate curve program (Appendix A1 or A2), and observe plate current I(VP) using Probe. Adjust EX and KG1 so that curves for relatively low negative grid voltages (e.g., Vg = 0 or -0.5 for the 12AX7 in Figure 2) match experimental data. Typical values of EX range from 1.3 to 1.4. Line curvature increases with EX. The textbook value of 3/2 for EX is appropriate for equations (1) and (2), where it gives a reasonable average representation of tube operation, but is not really accurate in all regions. KG1 is inversely proportional to plate current for given grid and plate voltages. It usually requires several runs to get a really good match for EX and KG1. MU may need to be adjusted slightly in the process.
For pentodes, the best estimates of MU, EX, and KG1 are obtained from triode-mode curves, i.e., curves taken with the screen grid connected to the plate. Such curves were available for the pentodes listed in Table 1. It is very gratifying to see how parameters obtained from the triode curves (Figure 4) result in excellent fits to pentode and ultra-linear curves (Figures 3 and 5). In running the pentode plate curve program (Appendix A2), operating mode can be set by adjusting parameter TRIMODE (0 for pentode, 40 for ultra-linear (UL), and 100 for triode). VG2NOM (quiescent screen voltage) must also be set appropriately.
KG2 is inversely proportional to pentode screen grid current (I(VG2) in Appendix A2) for given control and screen grid voltages. Curves for pentode screen grid current are rarely published, but screen grid current is usually included in tables of typical tube operation. It is adequate to match a point or two from these tables. KG2 does not need to be estimated with great accuracy to obtain good results in SPICE simulations.
KP (kP) dominates the behavior of the new model in region (A), which is characterized by large negative grid voltage, large plate voltage, and low plate current. Plate current is inversely proportional to KP in this region. Determining KP for a given tube is done entirely by trial-and-error. Triode-mode curves must be used to obtain an accurate estimate of KP for pentodes because published pentode curves tend to have insufficient resolution in region (A).
KVB (kVB) relates to the "knee" of the characteristic curves, and is defined differently in the triode and pentode equations. For pentodes, the knee is proportional to KVB, and is most visible in the pentode-mode curves (Figure 3 for the 6550). Equation (5) does not give an accurate estimate of the knee for all levels of grid voltage, EG . Fortunately, this is not a serious limitation because load lines for practical designs pass close to the knee for EG = 0. (Otherwise there would be a serious impedance mismatch.) The location of the knee for EG = 0 was used to determine KVB in Table 1. For triodes, the knee is proportional to the square root of KVB, and is only apparent when the tube is operated with positive grid voltage. Triode curves for positive grid voltage are published infrequently, for example, the 12AU7 in the Sylvania tube manual.
Figure 3. Circuit for obtaining triode characteristic curves.
Figure 4. Circuit for obtaining triode characteristic curves.

Figure 5. 6550A Pentode mode plate curves.

Figure 6. 6550A Pentode, Triode mode plate curves.

Figure 7. 6550A Pentode, Ultra-Linear (UL) mode plate curves.
Toroidal transformers have much lower leakage flux than traditional "EI" transformers (so-named after their core geometry). This results in an extremely large bandwidth. Their only drawback is that their extremely low magnetic circuit reluctance makes it necessary to balance the dc current in the two haves of the primary winding extra care. Table 2 gives parameters for the PAT-4006-CFB output transformer relevant to SPICE simulation. The PAT-4006-CFB is a semi-custom version of the 100W PAT-4006, available on special order, designed for four 6550 or similar tubes in push-pull-parallel. It has a 2 kohm primary winding and two center-tapped secondary windings: a 5 ohm winding for the speaker and a 20 ohm winding for feedback.
 
Table 2. Parameters of the Plitron PAT-4006-CFB output transformer
To develop the SPICE model (Appendix A3), the center-tapped primary winding with ultra-linear taps is divided into four mutually-coupled segments that have {0.3, 0.2, 0.2, 0.3} of the total number of windings. The inductance of each segment is proportional to the square of the number of windings: {.09LP, .04LP, .04LP, .09LP} = {35.325H, 15.7H, 15.7H, 35.325H}. The ratio of primary to secondary inductance is (NP / NS)2. The transformer's coefficient of mutual coupling, KALL, is entered into the SPICE data file:
KALL = sqrt(1-1/Q) ~= 1-1/(2Q)  (The approximation holds for large Q.)

Figure 9. Original PAS-3 line amplifier frequency response at first gain stage plate (3P)
and output (LINE_OUT). Generated by Probe.
The frequency reponse at the output meets the 20-20,000 Hz �1dB specification with no problem, but there is a huge 0.5 Hz peak at the first gain stage plate. Altough this peak is well outside the range of hearing it caused definite audible problems, especially on records, where the rotational frequency at 33.3 RPM is-- you guessed it-- almost exactly 0.5 Hz. It was a sort of grindy sound-- perhaps an intermodulation distortion component. A redesign, discussed in Feedback and Fidelity and SPICE and the art of preamplifier design, fixed it beautifully. Listings and excerpts from the output files are in Appendix A4 in part 2.
Output files PASorgTC.cir and PASorgTC.net were generated by schematics. Output file PASorgTC.out was generated by PSpice. Many of the lines in PASorgTC.cir are generated from Schematics by clicking on Analysis, Setup..., then working with the appropriate boxes. .LIB is followed by the name of the library file that contains subcircuits referenced in the program. .PROBE instructs the program to generate data for the PROBE program, which displays graphs of time and/or frequency domain signals at each node. .ac calls for an ac (frequency-domain) analysis, i.e., a frequency sweep with 20 points per decade from 0.01 Hz to 1 MHz. If present, .TRAN calls for a transient (time-domain) analysis, which is required if a Fourier analysis is to be performed.
Appendix A4C shows some of the results of running PSpice, including the dc voltages at each node, the currents drawn by the two voltage sources, and the total power consumption. The first tube is labelled TU3 because TU1 and TU2 were in the phono preamplifier. For example, the plates of TU3 and TU4 are at 168 and 196 volts-- about where they should be (a little over half the supply voltage). A Fourier analysis can be performed for time domain simulations.
Let A be the open-loop (non-feedback) gain of an amplifier. Let B be the fraction of the output voltage that the feedback circuit subt
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