A situation in place was the next – my half done amplifier was working already 3 years just proving the statement “there last longing device is a temporary one”. It was kind of fine – but it consumes an energy. In a fact a solid chunk of the energy – it is class A amplifier. At some point in time I started to think – why to not switch on/off the amplifier in dependence on the signal presence.
Auto enabling/disabling of the amplifier