This transformerless 16-ohm speaker circuit was found in a Radio Electronics from October 1963. The circuit is powered by 12 V and the gain is 50 dB.
This circuit is recommended for alarm systems since it has a good output stage. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...