This interesting circuit for the RDA8851 allows you to obtain two volumes with a simple touch. The circuit is from an Electronics Now from December 1988. Note the amplifier voltages.
This circuit is from an old technical documentation from Spain. The circuit uses a FET that is...
Using transistors at the time, this circuit was found in a 1967 Ferranti documentation. The...
This circuit is from a thyristor manual from On Semiconductor. It makes use of a PUT and a SCR...