1st single electron tube power amplifier ever?

At you risk. High voltage is very dangerous, take all safety precautions. It works and sound amazing. The Pleiades DL94 single ended direct heated triode battery powered power amplifier in class A with an input transformer to drive the output electron tube to music beauty glory! So all needed is: an 1:12 input transformer, a 220nF coupling capacitor to control grid, a 560ohms cathode resistor with 220uF capacitor in parallel for bias and no local feedback respectively, a DL94 electron tube triode connected ie anode connected to screen grid, a Sowter SK05s 2.5K to 8 ohms output transformer, a 2AA battery holder with 2 AA batteries for heater voltage, 2 4AA battery holders for 16 4LR44 6V batteries (8 small paper cylindrs of AA size is constructed by wraping gently 2 4LR44...), 2 switches for low tension and high tension, a fuse for high tension, a fuse for low tension is also needed. It may be also possible to construct the same amplifier without Any resitor or capacitir (sic) by using 3 battery power supplies as in the early 1900s, Va for heater, Vb for plate (anode), Vc (-6V) for bias through the input transformer. This particular schematic looks like all 3 battery supplies connected in series, left Vc, middle Va, right Vb, negative side of Vc connected to one side of secondary of input transformer, other side to grid. Vb positive side connected to primary of output transformer. So far only the a bit more complicated version has been constructed on top of a red linoleum approx A3 size sheet, and all connections are done with Wago connectors. How does it sound like? 1st of all signal path: Careless Whisper - George Michael from Wham vintage compilation CD - Sony cd Walkman line out - (Sowter input transformer is inserted on Finder relay octal base, so if lower volume is needed a 1:7 Sowter octal transformer is pluged in insted of 1:12) so Pleiades DL94 as described above - Celestion Ditton 150 loudspeaker (so far just one monoblock power amplifier is made) at about 1m to 2m from listener - Small quite a bit reverberent listening room with 3 betoumin roofing felt low frequency absorbers inserted on big canvas panels, the big one is behind the speakers in this control room - listener. Only 0.4 Watts of pristine quality. It sounds huge, with deepest bass, amazing mid range, and untiring bass, mid, treble depth. The sax on Careless Whisper comes to life inside the room as all the instruments and George himself. Same for Is it a Crime - Sade for its miraculous recording with the amazing muted sparkling trumpet at the end, it sounds so lifelike, goosebumps to use a phrase from recording engineer bruce Swedien. The voice of Sade sweetest as ever even at high volume, same for Whitney Houston. This amplifier does not corrupt music at the loud moments of the song. It just overflows with music beauty. Why not, it is just one triode electron tube producing only its low order overtones at high levels. By the way the Pleiades one transistor 2N3053 (2 for stereo) sounds amazing too as it is the almost the same schematic, a bit simpler. It is possible that the electron tube version sounds even better, it is also higher powered 400mW compared to 2x100mW since the transistor version is at the moments powered by 12V at 12mA. the electron tube version is powered by 90v, 8ma. Many thanks to Vicky who first pointed out how amazing the Pleiades 2N3055 single transistor amplifier sounds. The versions with output transformer as those mentioned today are much more energy efficient and sound loud enough even with modern (non horn loaded) speakers which have so low efficiency. Output impedance of DL94 with particular ratio output transformer has been measured 11 ohms. So the output voltage increases a few dB for frequency where the inpedance of the speaker rises. Never the less the Ditton sounded huge and amazing with the Pleiades DL94. Unbelievable bass that caresses listener's stomach without sounding any boomy. If the cathode capacitor is disconected the gain drops, bass perhaps sound deeper. This amplifier recreates the beaty of music and makes the experience feel like a ceremony. An amazing tool for teaching yourself music.