Free Programs you can download.

Replacement EXE files.

Once you have the program installed there is no need to install it again. To update your favorite program look for a replacement EXE file for it.

You may wonder why the programs are designated for Windows 98. What ever your personal opinions about Microsoft, you have to give them credit for maintaining forward compatibility. But they have not been so good about backward compatibility. Programs compiled under Windows 98 work just fine under Windows XP but those compiled under XP aren't at all happy when run under 98. I don't know how Vista will fit into this picture. I'm still awaiting feedback on that subject. Meantime, as far as I am able to tell you can install these programs in any version of Windows from 98 to XP without problems.

Of course there are never any guarantees. When you download programs from any site such as this you are taking some degree of risk and it is all yours. I am not responsible for any damage to your computer or its operating system or any other damage or losses you may experience as a result of downloading, installing, and using, the programs from this site.

However, I can promise that there are no viruses, Trojans, worms, spyware, or any other deliberately malicious code in these programs. I will provide email help but that's as far as I can go. I'm not a company after all and you shouldn't expect me to be. How much did you pay for the programs? They are worth more than that. They are the best I can make them but I am only human. I DO make mistakes.

Operating System.

I found to my dismay that a program compiled under the Windows XP operating system would not install correctly in Windows 98. The only solution I could find for this problem is to maintain two computers, one running 98 to compile the programs on and the other XP for daily use. Below you will find a link to only one page, for 98 programs. If you have visited here before and you remember XP versions of the programs, they have been taken down as explained above.

What about the rest.

We are now down to one size fits all. This version will install on windows 98 or later. Be on the lookout for a dialog box that comes up stating that a file to be installed is older than the same file already on your computer and asking if you want to replace it. Read the question carefully. Sometimes the question is stated positively and sometimes negatively. You want to keep the newer file. You don't want to replace the file with an older one.

If you are using a very old version of Windows 98 you may get a message that some files on your computer need to be updated. This isn't very likely because I am running a very old version of 98 myself. If you should get this message it seems alright to let it happen but only in Windows 98. If you allow a file to be replaced with an older one you are asking for trouble. In every instance I know about the install will continue if you say to keep your newer files.

What's Available.

At present there are six programs available. They are

  1. Audio Amplifier Design.
  2. Circlotron Amplifier Analysis.
  3. Class AB Amplifier Analysis.
  4. Electronics Calculator Suite.
  5. Power Transformer Calculator.
  6. MaxCAD, a schematic and chassis layout drawing program.

Audio Amplifier Design.

The main feature of the audio amplifier design program calculates the open loop gain from tube manual data you enter and then determines how much driving voltage is required with a given amount of feedback. There are auxiliary calculators that will provide the resistor values for the feedback network and the gain of resistance coupled amplifier stages with varying amounts of cathode degeneration based on data from resistance coupled amplifier charts found in the back of most tube manuals.

Circlotron Amplifier Analysis.

This program has grown out of a topic that came up on the Fun with Tubes email list. I have spent many hours breadboarding and testing the design and at this writing I am still not finished with everything I want to do. I wrote this program to help me figure out what was going on. It gives important information such as the peak cathode current, and the plate dissipation, of one tube. If this arouses your curiosity, see Circlotron Amplifier on this site.

Class AB Amplifier Analysis.

This program starts by asking you to enter the following data from a tube manual for a push-pull class A, AB, or B, amplifier. You enter the following four pieces of information.

  1. Zero signal plate current, in mA.
  2. Maximum signal plate current, in mA.
  3. Plate-to-plate load impedance, in ohms.
  4. DC plate supply voltage, in volts. When using cathode bias be sure to subtract the bias voltage from the plate supply voltage. For example, if the B+ voltage is 250 volts and the cathode bias is 20 volts you must enter 230 volts in this box.

When you press the calculate button the following quantities will be calculated and placed in the boxes below the "Calculated Results" heading.

  1. Peak plate current, each tube, AC component only, in mA. The plate current of a tube always has a DC and an AC component. Because the load is transformer coupled, only the AC component contributes to power in the load.

  2. Peak plate voltage, each tube, AC component only, in volts. Same as above. This quantity swings negative and positive.

  3. Peak plate current, each tube, AC + DC, in mA. If you had one of those expensive current probes for your oscilloscope, you would be able to see this quantity. It varies from zero to a peak positive value.

  4. Maximum plate voltage, each tube, AC + DC, in volts. This is the maximum voltage you would observe using a standard voltage probe with an oscilloscope. The tube manuals never tell you this but it can be important for the voltage rating of capacitors in the plate circuit, if any.

  5. Minimum plate voltage, each tube, AC + DC, in volts. This value is of interest to indicate how close to saturation the tube comes.

  6. Plate dissipation, each tube, in watts. Once again this information is not given in tube manuals but it is very important. Every tube has a maximum dissipation which must not be exceeded in operation. You can change the value of maximum signal plate current to see how this effects power output and plate dissipation.

  7. True RMS power in load, in watts. This quantity, like the plate dissipation, is derived using numerical integration. That means it is correct even when clipping is taking place. This might be of interest to see how overdriving the amplifier will effect the plate dissipation of the tubes.

  8. Earliest angle of non-conduction, either tube, in degrees. In class AB and B amplifiers, each of the tubes goes into cutoff for part of the cycle. This angle is the number of degrees after the AC component crosses zero. If the angle were 5 degrees, the start of cutoff for one tube would be at 5 degrees on the AC wave and the start of cutoff for the other tube would be at 185 degrees.

  9. Total cutoff angle, either tube, in degrees. This gives the total angle during which either tube is in cutoff.

  10. Checksum. Maximum signal plate current, back calculated, in mA. The use of the word "checksum" is not quite correct here but take my meaning not my literal words. I put this in as a check on the calculation logic. If you set the maximum signal plate current high enough to produce clipping, this number will not agree with the value you entered.

  11. The last box contains no text but turns red to indicate clipping or green to indicate no clipping.

There is no help file with the program. You are currently reading the instructions for using it. It includes a feature in which the data from the last run of the program are saved to disk and reloaded the next time it is run. The data that are displayed the first time you run it are from the last time I ran it.

Notice that even the calculated values are filled in. If you change any of the first four values and click the "Calculate" button, the other values will change. You can manually change any of the calculated values, but they will change back when you click the calculate button.

Because there is no place to input the screen grid voltage, this program works for triodes as well as pentodes. The only restriction is that it is for push-pull amplifiers only. If there is sufficient demand, I can add a checkbox and the necessary code to switch it over to single ended calculations.

The program causes tube saturation at zero volts plate to cathode. Most tubes saturate anywhere from 50 to 100 volts but I did not incorporate an input variable for this quantity, so it is set at zero. If there is demand for this feature I will add it.

As indicated above the power output may be adjusted by changing the maximum signal plate current. Of course you can change any parameter you want. The only restriction is that the maximum signal plate current can't be less than the zero signal plate current. If you make this mistake the program will tell you and let you change it. You can't burn anything out by running a computer program so you can go wild with current, voltage, and power, if you want to. Have fun.

Electronics Calculator Suite.

This sweet of electronics assistance contains 20 separate calculators that make designing electronics much less arduous. Here is the list.
  1. STANDARD VALUE VOLTAGE DIVIDER finds the closest standard 5% resistor values for a voltage divider. You may specify the divider by its attenuation ratio, attenuation in dB, or input and output voltages. You also may specify a current load; such as the screen grid of a tube, a fixed resistance load, or no load. The output gives a number of choices giving the percent error of each.

  2. WAVELENGTH AND FREQUENCY works the familiar wavelength/frequency formula but also gives you the option to ask for half wave antenna lengths, with end effect factors, and tuned transmission lines with velocity factor. Output is selectable to be in meters, feet, or feet and inches.

  3. C-Xc L-XL AND RESONANCE presents you with the opportunity to enter frequency, capacitance, inductance, capacitive reactance, and inductive reactance. Anything which is blank or zero will be calculated.

  4. R-L-C SERIES CIRCUIT AND Q presents boxes to enter frequency, bandwidth, capacitance, inductance, resistance, and Q. As above any missing quantities will be calculated.

  5. L-NETWORK MATCHING designs an L-network to match the plate of a tube, or transistor, to a low impedance load such as a mechanical filter or antenna. You may enter the voltage and current of the amplifier or the effective resistance. You could also mentally turn it around to match a low impedance transmitter to a long wire antenna.

  6. CAPACITIVE DIVIDER MATCHING gives the design of a somewhat more flexible matching network. It works much the same as the L-network above but you can specify the Q instead of taking whatever the design gives you.

  7. CAP DIV WITH LOSSEY COIL is to be used after designing a network with the above calculator. When you invoke this one the design values are displayed but you may enter a value for the coil resistance. Pressing the calculate button gives you the loop currents, input impedance, and other information. You can make changes in any of the values to see what effect they will have.

  8. PI-NETWORK MATCHING designs our old friend the pi network.

  9. PI-NETWORK WITH LOSSEY COIL allows you to play with the coil resistance and other values to see how they effect the input impedance.

  10. FREQ. MULTIPLIER AND PRIME NUMBERS helps you design a frequency multiplier chain while avoiding those dreaded prime numbers. You enter a desired output frequency and a range of crystal frequencies and the program finds a series of multipliers, factors, for you.

  11. TRANSISTOR BIAS CIRCUIT DESIGN will design a constant voltage, 4 resistor, biasing circuit for a bipolar junction transistor. All resistor values come out in standard 5% values and the power dissipation of each is also given along with the dissipation of the transistor.

  12. BIAS STABILITY plots a graph of collector current versus transistor current gain (beta) based on the design in the calculator above. Beta changes with temperature so it is important to know this effect. You can play with the stability factor to get the desired stability.

  13. TRANSISTOR BIAS, CHANGE VALUES permits you to examine the effect of resistor tolerance variations on the operating point. The values from the above design are placed in the boxes but you may change them to non standard values to see what the effect will be.

  14. FEEDBACK performs those simple but tedious calculations on feedback amplifiers. As in other calculators you enter zeros for what you don't know.

  15. 6 x 6 R + j X works out those dreaded loop equations. You may enter the data as the coefficients in the equations, the impedances in the circuit, or the component values in the circuit.

  16. POWER TRANSFORMER is the same as the stand alone program by the same name. You enter the measured resistances, the voltage and current, if known or can be guessed at, of each winding and the program will give you the amount of power being dissipated by each winding and the transformer as a whole. If you are measuring the voltages of non loaded transformer windings you just check the box and the program will correct for load current.

  17. POWER SUPPLY FILTER SIMULATOR will plot out a graph of the instantaneous rectifier current and voltage across each filter capacitor. After you close the graph a set of statistics will be displayed.

  18. OSCILLATOR AND RF TRACKING gives the values for inductor, padder capacitor, and trimmer capacitor for the oscillator and RF tuned circuits in a superhet receiver.

  19. VSWR FROM R + j X AND R X METER will give you the VSWR based on the readings of an impedance bridge of the type R + j X or the H P R X meter.

  20. VACUUM TUBE AMPLIFIER GAIN gives the gain of a tube amplifier based on the amplification factor, transconductance, and plate resistance, of a tube. The gain is given with or without cathode bypass capacitor.

This program comes with built-in examples that will help you figure out how to use each calculator. The first time you run the program the files will be created. After that the file for each calculator will contain the data from the last time you ran that calculator. The original examples may be restored at any time by pressing the "Restore Examples" button.

I'm sure there are some spelling errors to be found and fixed. I won't be offended if you notify me about them.

I have been using these programs in old style BASIC for several years and in Visual BASIC for several more. There are always hidden bugs so if you find any pleas let me know. Tell me exactly the values you entered and what action precipitated the bug.

Power Transformer.

This is a stand-alone version of the very popular power transformer section of the Electronics Calculator Suite. In order to use it properly you need to build the Low Resistance Adapter described elsewhere on this site. To use this program you enter the measured resistance and measured output voltage of each winding. The program will make educated guesses about how much current each winding will safely deliver. The figures are somewhat on the conservative side. If you want to you can edit the CONSTANTS.DAT file. The file contains enough information to enable you to do this. If you overload and burn out a transformer, don't blame me.


This is a schematic diagram drawing program. Although that is its primary purpose it can also be used for chassis and prototype PC board layouts. Simplicity of use, on-screen prompts, and truly helpful help files should make it easy to use.

Latest Update.

Lately I have been adding many improvements. Just a few are, a list of most recently used files, allowing text and other shapes to be used in shape files, two new methods of drawing an arc, and loading of backup files from the menu.

There is still an issue with transferring files between computers having different screen resolution settings. After loading such a file you may see only part of the drawing, or it may not fill the screen. Pressing F11 will re-center it and set the zoom to 100%. I have yet to find a solution to this problem.

At Last the Downloads.

Many commercial sites I have browsed offer versions of there programs for sail and other versions that are free. The free versions are well hidden so you will get tired of looking for them and pay for the program. I wonder if you were beginning to think I had done the same thing. Well, here is the link.

Programs for Windows 98 and later.

The page has instructions for downloading and installation. The instructions are at the top of the page and the download links are near the bottom. Don't give up looking, they really are there.

Good luck. May gremlins and poltergeists stay away from your computer.


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This page last updated May 5, 2008.