We show in this article a channel of an excellent stereophonic amplifier using the known EL84 or 6BQ5 tubes. The circuit can be powered by several input voltages and has several output impedances given by the circuit manufacturer's code, since it is a commercial circuit.
This circuit is found in amplifiers of the brand Geloso (Italy) having been very successful in the decades of 50 and 60. The exit in push pull provides something around 10 W of exit.
The power transformer supplies an output voltage of 250 V with diodes being used in the rectifying sector, which was a major advance for the time.
In addition to the valves, the critical components are the transformers. In the case of the output transformer, specific types must be used for the valves indicated, but adaptations can be made for the power transformer.
Note that the power transformer has a smaller second voltage winding which independently powers the preamplifier sector.
In figure 1 the complete diagram of the amplifier for a channel.
