We found this 4 W amplifier in an old Argentine publication of the 70's. The circuit can be made with more modern power transistors like the TIP31 and TIP 32 in the output and BD135 and BD136 as drivers, but the transformers are critical elements in the design. If the source is used, it should be 6 + 6 V instead of two batteries. For the preamplification sector, ordinary batteries can be used, since the consumption of this stage is low.
