6J52P amplifier - the main scheme
6J52P amplifier - power supply
Five months ago I decided to do experiments with simplest audio amplifiers based on a single tube. I had not expected good sound characteristics, but I like simple engineering and I could be happy even if resulting sound is not perfect. It is a good way to learn more about history of radiotechnics by reading specialized books and magazines. But this was never enough for me. I prefer to make something described in magazine instead of just reading an article. So, let's describe the first scheme I tried.
Note that here is drawn a full scheme of stereo sound amplifier.
Few words about elements. I have used soviet 6J52P tubes and I don't know which is european analog. In power supply I included 6Ö5Ñ vacuum tube; feel free to use any other vacuum rectifier instead. Output transformers have 35:1 transmittion ratio and relatively low inductance of the primary coil (no more than 10 H). If your loudspeakers work well on frequencies lower than 40 Hz, feel free to use transformers with higher inductance.
The amplifier was built in small plywood box. Power supply was placed inside, all other elements were connected to the top panel.
After three months of daily use of this cool amplifier (I loved it and had no plans to build anything else) one day I was boring and decided therefore to make a new amplifier. But which differences should it have? First of all, I decided to use single triodes instead of pentodes. Another feature - low level voltage of power supply.
You should understand - to make sound amplifier on single tube we should use such tubes that have high transconductance. Soviet 6N23P tube is excellent choice due to this reason. It has that parameter equal to 23 mA/V when both triodes in single tube are connected in parallel. The new scheme is very similar to shemes shown above.
Soviet rectifier Ä210 in power supply could be replaced by any other rectifier that can work with high voltage and can hold above 100 mA of current.
The amplifier was built in a very small plywood box.
How do I use my amplifiers? First of all, the second scheme has extremely detailed sound, but relatively low output power (no more than 0.5 Watts per channel). Usually I listen contemporary classical music on it: great pieces of Kancheli, Artemiev, Stockhausen. The first scheme, based on 6J52P tubes, I use for anything else. I had listened Traviata and Don Carlo operas by Giuseppe Verdi many many times using that amplifier.
Of course, I use my amplifiers with finely tuned hand made loudspeakers. Nominal resistance of them is 4 Ohms.
As you can see, both schemes are very simple and easy to build. Enjoy!
P.S.: If you have no tubes used here, try to use anything else. Maybe you will have less output power, but in any case the amplifier should work (don't forget to adjust voltage of battery and power supply dependant on type of used vacuum tube).