ULF bass reflex on one first transistor. Numerous calculations and experiments to create powerful high-quality low-frequency amplifier has led me to believe that the most promising way to the design is to use a phase inverter on one first transistor. It is curious that such amplifiers could be forty years ago, but this has not happened due to a number of reasons.
First of all, by creating transistors with n-p-n-junction have the opportunity to separate the signal due to the properties of the transistors, since some of them are open positive pulse and the other negative. Amplifiers such transistors can be substantially simplified, however, on their release there was significant distortion of the signal. To get rid of them, radiokonstruktor began to complicate the scheme of amps, not to seek other ways of diagramming the ULF.
And another, perhaps the main cause of rejection of schemes with the phase inverter to the first transistor was a significant overheating of the output transistors of such amplifiers that exclude them from any long-term operation at high output power.
All these considerations made me a musician and composer, carefully analyze the well-known schemes of ULF in order to find the cause of the distortion. I went his own way, relying on their knowledge of the “tube” electronics. For this I had to learn how to design and calculate components, creating hundreds of experimental models, in the end I managed to find the cause of the overheating and eliminate it. In the end, I developed a low-frequency amplifiers operate at supply voltage up to 90 V, while the output power of about 300 watts.