There is a great article on Glass Audio called try Battery Tubes - Larry Lisle

Thank a lot Larry Lisle for inspiration. This artcle was possibly handed to me by someone who was working at an electronics lab at the Airport of Ellinikon when doing my military service and a good officer who apreciated my grandfather George sent me to the music department of the Airforce. We were discussing with this technician the 1H4 triode.

My grandfathers, grandmothers

From my mother side, Manolis born in Crete, singing till late age on Church. Eleni from Prusa, sweet voice. From my father side, George from Smyrni, played a bit a stringed instrument, had to move to Athens and then went to US for many years then came back to Athens. Maritsa from Prusa, played a bit the violin. My great grand father from my mother side, Menelaos, gifted me a real piano. He enjoyed listening as well as my other grandfathers when i was a kid my first single ended transistor amplifier with tiny output transformer connected to some Sony low impedance headphones (attention protect yur hearng, never play loud on headphones, even on speakers). It was connected to an AM broad bandwidth radio. Both were from the games PolyKyclomatic 501B and 1002 which allowed making electronic constructions connecting components with small springs. Each node of the circuit was a spring. When the miracle amplifier (as it was descibed on the manual) was built all i could hear was a click on the little speaker when connecting the 9 volt battery. i was so sad, i thought it did not work. i did not know that i should connect a music signal to amplify it. i miss them all as well as my godmother Soso who gave me her piano, Godfather George who gave me his Grundig single ended stereo radiogram, Godmother Elsa who tried to teach me some chemistry. It feels like they all still help me from above. My parents kindlty immedeatly bought for me these electronic construction games when they were seen at a 3rd or 4th class primary school party. The older brother or cousin of my schoolmate George or Dimitris were playing and experimenting when i opened a bedroom door by chance.

Eureka! Just a step up input transformer, one electron tube and a step down output transformer class A no feedback power amplifier, it works beautifully!

At your risk, please take every precaution. Eureka should not be used as it may not be important. But it is important to me. I have been building amplifiers since the age of 7 and now that i am 52 and feel like 18 it is the first time in my life that i can listen to a no resistor, no capacitor, just one electron tube, 2 signal transformers, and some batteries, music power amplifier. It is the Pleiades DL94 described on previous posts but further simplified. The DL94 electron tube is again triode connected> There are now 3 battery power supplies. Va is 2 x (AA rechargeable 1.2V) suppling heaters with 2.6V. Vb is 8 x (AA size 12V created by 2 4LR44 in series) supplying (anode connected to grid 2) with 94V through the output transformer primary. Vc is 2 x (CR 1/2 AA 3 volt) supplying control grid with -6V through the secondary of input transformer. That is all. It works and sounds mysteriously beautiful with huge bass from the big Sowter SK05s output transformers converting 2.5Kohms to 8 Ohms. The trick is also the input transformer which is a microphone transformer with a step up ratio of 1:12 so an extra voltage ampliying electron tube is not needed! On the more complex cathode resistor, electrolytic capacitor, coupling capacitor to grid version, bias was -4.8v by the 560ohm resistor, and anode + G2 (triode connected) current was 8.6mA. Now with -6.5V fixed bias current dropped to 6.3mA. So the ground connection should possibly be moved as on the French Radio Tubes manual from negative heater voltage to positive heater voltage since there is a distribution of electric potential across the heater filament. Or the bias supplied changed etc. Signal path. Careless Whisper - Wham or Big in Japan - Alphaville on original CDs - Sony CD Walkman line out - Pleiades DL94 - Celestionj Ditton 150 at listening distance of 1m to 2m - Small bedroom with low frequency panel absorbers wit enough reverberation in middle range. This amplifier sounds perhaps less loud that the cathode bias version with an uncertainty on whether there is some kind of subtle distortion, which may be becaude of less anode current since the fixed bias voltage seems to be too much. This on Careless Whisper. Big in Japan sounded like an undistorted 80s club. Every instrumenbt so clear, descrete, with decoded melody, undistorted. Even in loud passages since it is in class A amplifier ie electrons flowing all the time. i have never heard Big in Japan in this way. But it may be because it is the first time listening to it on CD. By the way these minimalist amplifiers including the Pleiades 2N3053 single transistor amplifier make the CDs a revealing experience with the missing octaves on high frequency added/ So it it sounds like a good quality close to master tape record. Listening test was with a monobloc amplifier fed by the right CD channel fedding the right loudspeaker.

A liitle instrumental

Just made up by Philippo, George while Fransesca was taking video and giving good vibrations. The melody repeats La, Si, Do, LA, Si Si, Do, La La, Si, Do,...etc. The bass is La, then Fa, then Re, then Mi. So suitable bass code ie harmony or chords is La minore, F majore with majore 7th, Re minore with majore 9th, Mi minore with minore 7th.

A Vc battery for bias

At your risk. Please take all safety precautions, including the millitary trick of one hand always in the back pocket. The Pleiades DL94 single electron tube power amplifier and almost nothing else except input and output transformer may be tried with fixed bias Vc of -6V. Panayiotis at Disios had the brilliant idea for the Bulgin AA battery holder to use 2 CR 1/2 AA 3V batteries by Varta in series inside the cylinder. 2 Bulgin 4 AA battery holders are being supplied by Fanos for the VB supply (see previous posts). Then one AA battery holder for heater Va. Hopefully with them the amplifier can be constructed to look exactly as the simple schematic, looking physical components from above. Then everything enclosed with see through plexiglass in color?

There is an analogy between single ended amplifiers and human speech, singing production

When we speak or sing there is not one entity pushing air and another pulling it. It is just one person doing the thing! A constant flow of air originating deep inside our body is being modulated by the vocal chords which control this flow like a grid inside an electron tube or electronic valve. A constant flow of electrons in a class A amplifier is modulated by a control element be it the grid, the base, or the gate. As the signal output from the amplifier tends to 0 so does distortion tends to 0. If we overdrive after limits distortion will become serious but gradually as everything else in nature with no negative feedback. Same with an output transformer, if one exceeds its limits. Gradually.

Tubes vs Transistors vs MOSFETs, is there an audible difference?

At your risk. Please take all safety precautions. The title is paraphrasing the beatiful article by|Russel O. Hamm... The Pleiades 2N3053 power amplifier in class A consists of just one 2N3053 transistor, a battery, a fuse, an output transformer, a bias resistor, and an input coupling capacitor. The Pleiades DL94 is almost the same circuit with a DL94 electron tube. It is about to be further simplified by building another one with no capacitors or resistors. Just an input ransformer, an electron tube, an output transformer, a Va battery, a Vb battery and a Vc battery for bias connected to the input transformer. The bipolar transistor 2N3053 may be further simplifier by including an input transformer and a similar kind of bias arrangement trough this input transformer. The input transformer is very important for the electron tube version as it provides x12 voltage gain, so that a driver electron tube is not needed and the whole job feeding the loudspeaker with music through the output transformer is done by just one electron tube. While explaining this to Panos, he sugested|i read Susan Parker's post on diyaudio on her push-pull, input transformer - MOSFET - Output transformer amplifier. Inspired by them why not making a Pleiades single ended MOSFET class A amplifier. Just an input transformer, a MOSFET and an output transformer. If the MOSFET is an enhancement type it may be possible to do away with external bias? But first trials will be with an IRF740 depletion type MOSFET given to me by Grigoris. The bipolar, electron tube versions sound so beatiful. How would all 3 types of amplifier, bipolar, electron tube, MOSFET compare on such similar, minimum component possible environment?

Transformers may be the most linear devices on the planet

Chances are we were conceived while our parents were listening to a song produced with many signal transformers. For example Take on Me - Aha, the lead vocal by Morten Harket sung on a Neumann U47 microphone which has the output transformer right inside it after the VF14 electron tube inside the mic... Anyway the nonlinearity of the metal is exactly compensated as the transformer produces and then reproduces itself. A varying electric field at the primary (the input music) is converted to a varying magnetic field, and then this magnetic field flowing inside the iron is converted back to an electric field at the secondary (the output music) by Faraday's law of induction. Furthermore since by this law the voltage is proportinal to the rate of change of the magnetic field, since increased music frequency means increased rate of change, it follows that as frequency increases magnetic flux must decrease to keep flat frequency responce. So distortion decreases too as frequency increases (only transformers and dynamic (moving coil) or ribbon microphones can do this) so they create very little intermodulations distortion compared to triodes, bipolar transistors or MOSFETs. Further reading: Audio Transformers - Bill Whitlock - PDF

A class A no feedback power amplifier with just an input transformer, a MOSFET, an output transformer, a battery and nothing else?

At your risk. Please take all safety precautions. What if an enhancement MOSFET is used, it is on at 0 volts bias so that step up input transformer is directly connected between source and gate. Then output transformer (with air gap to avoid saturation by DC current) is conneted to drain through a battery whose negative terminal is connected to source to close the circuit. Thats's all folks.

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.