Stereo from mono

Sometimes ideas occur, which, although good in themselves, cannot be implemented because the necessary technology is not yet there. Consider, for example the possibilities if one could obtain stereo reproduction from a mono amplifier. Although the idea seems far-fetched, in principle this can be achieved by multiplexing the left and right channels, i.e. feeding the left and right channel information alternately through the mono amplifier. Figure 1 shows a design where only the preamplifier is common to both channels, whilst in figure 2 the power amp is also included.