Electron Tube Class

From HacDC Wiki


Some people have made the mistake of expressing interest in electron tubes. They're about to learn more than they bargained for.


The first session was a great success. We covered the first item in the syllabus and part of the second.

The next session will feature a brief review of the first session and finish covering the second section. I think it should be possible to reach the section on advanced circuits. during the next session.

I also owe you guys a tube dissection, I'll try to work that into the next session too.


Next class: Aug 11 at 7:30 PM.

Silly Bus

  • Thermionic emission: From the lightbulb to the pentode.
  • Fundamental circuits and coupling
  • Push-pull and Phase splitting circuits
  • Transformers in single-ended and push-pull.
  • Advanced circuits
  • Tube failure modes
  • Hands-on experience building a battery-powered single tube filamentary pentode pre-amp.
  • Power supplies and tweaking.
  • What is the real secret to great sound?

Laboratory Supplies

cheap demo pre-amp

Go to [] and obtain what you think is the most informative datasheet for the following tubes and print out a copy. -- you need a physical copy.

filamentary diode 5U4* Optional: GZ34 / 5AR4

canonical triode 2A3 Optional: 845

to explore gain versus output 6SN7* 6SL7* or 12AX7 / ECC83

Pentodes 6BQ5 / EL84 Optional: KT88, EF86

3S4 <<< absolutely required, this is the tube we're using.

Suggested Reading

Radiotron Designer's Handbook 4th ed. [] Might have one lying around.

Tube Circuits for Audio Amplifiers (1-882580-03-6) features some very elegant and practical designs.

An Approach To Audio Frequency Amplifier Design. (1-882580-05-2) Has some good discussions about output transformers and ultralinear design. Then it starts out with some nice practical amps but, before long at all, starts talking about 1,100 watt monsters with 2.5KV power supplies.

Building Valve Amplifiers (0-7506-5695-6) is probably too practical to be enjoyable but I have to deem it essential. His other book is fantastic, one of the most well worn tomes in my personal library, but get this one first.