After a long wandering and quarrels with high-end gurus, I sat down and repeat Andrea Chifoli's amplifier, namely:
Which appeared that sound pretty well. Once I shared with some friends what I did, they advised me to try to change the tubes' bias points, because they were far from optimal. I listened to them and changed the cathode resistor to 510 ohms wire, which was not so smart. After a few experiments I stopped at 180 volts for Anode, 390 ohm resistor in the cathode and -8.5 volts bias, and increased and cathode capacitor up to 1500uF. A few people have heard this amp and have shared that sounds pretty well (I hope they are sincere), thus since some improvements with elements the sounding have improved even more. I put VR6 Vladimir Ryzhkov output transformer, Audio Note & Shinkoh tantalum for cathode resistor, and for the surge capacitor I used Black Gate NX series. All wiring is UP-OOC Cupper Neotech. Filtration also used Black Gate VK and WK, my idea was not to allow compromise with equipment and after all get the following.
A couple simulations:
Input and output signals:
Output power as a function of input signal:
And finally distortion:
As you can see for 0.6 volt input level the distortion is below 0.5% which according to my requirements is more than well. Well it's shortly after numerous advice and guidance of friends I became the owner of this gem and for a price of less than 800 leva.
I want to thank Simon, Andro, Velin and Kruger for assistance rendered in the creation of this amp.
And here is a photo of the finished amplifier I created: