A Practical Guide to Designing Tube Amplifiers (PG2DTA)

I've been reading the Radiotron Designers Handbook Version 4 (25MB PDF), the Morgan Jones Valve Amplifiers book, Steve Bench's web pages, and a number of other old books, but there is one thing I cannot seem to find described well - the single-ended amplifier. Maybe its just so simple that nobody goes over it in detail. Maybe its because the authors wanted more power so they focused on pentodes, push pull amps and feedback. Maybe I just missed the forest through the trees because I don't understand all the math and terminology. Whatever the reason, those books don't work for me. While the Boozhound Laboratories site is a great starting point, there are a number of places where I want to know the general idea of why a value was chosen so that I can design my own amplifier.

So here is my Practical Guide to Designing Tube Amplifiers (PG2DTA). I'm going to start with the following circuit - which is about a simple as you can get. There are two stages; a driver stage and a power stage. Personally, I like to refer to the power stage as the output stage, but for the purposes of this guide I will call it the power stage because many of the texts refer to power amplifiers and most websites refer to power tubes.


As you can see, the circuit does not include the values for the different tubes, resistors, capacitors, and voltages. In addition, the power supply is not represented in the diagram except for the magic B+ symbol. I call it magic because it seems to me that B+ is frequently referenced without any details of how to get it.

I have broken down the approach to determine which values to use into the following 10 steps:

1. Choose a power tube
   
2. Determine the output transformer to use
   
3. Determine the operating point
   
4. Calculate the cathode resistor, grid resistor, etc.
   
5. Choose an appropriate driver tube
   
6. Determine the load
7. Determine the operating point
8. Calculate the cathode resistor, grid resistor, coupling capacitor, etc.
9. Choosing a power transformer
10. Modeling your power supply with PSUD

Later I will expand the guide into different areas. For example, going from a single-ended output stage to parallel output tubes or different drivers stages (mu follower, srpp, etc).