Celeste (in bottom to the page n. 2 photos) thanks to the employment of the interstage transformer, completely concur the direct pilotage of the final transistors (not darlinghton or mosfet) with one stage pilot with valves, of elevated musical quality: a circuit Williamson, realized with two ECC82 for channel, to notice that the transistors designed in red they do not make part of the beacon circuit, but of that one of polarization and thermal stabilization.
This choice allows one ability to pilotage in the highest current, much difficult one to catch up with traditional outlines, less than not to increase the number of the gain stages on the distance of the beacon.
Interesting is also the escape cap, pure to tubes, with characteristics of listens of highest level.
Draft of an apparatus that demands a sure engagement, you would not advise it less expert, species in the realization of the circuit of polarization, therefore important to the aims of the stability regarding the temperature and to the point of operation, of which ago it leave the interstage transformer, whose calibration goes made with extreme cure.
The operation is in class A2, that is works in class A for good part of its dynamics.
I have used in total six transformers, 3 printed circults, 4 dissipators, an amount of condensers for a total of beyond 300,00 microfarads.
You notice yourself that this amplifier being directly coupled to the loudspeakers without transformer or condenser, must preview a protection for the separation of the load in case of breakdown to one of the final transistors, with functions also anti bump to the switch on and to the switch off.
Particular to open heart
by Alessandro Coppi