The original version of this circuit was suggested by an old Radio Electronics (1990). The circuit can be assembled with the pair BD135 and BD136 and with some changes we made in the original design. Note the high impedance speaker. With the BD pair can have a lower impedance for the speakers and higher output power. The circuit gain is given by R1. The power supply must be symmetrical with excellent filtration. The input is high impedance. The output transistors must be mounted on small heatsinks.
