Power amplifiers with selector Class of operation?

This is typically a feature that allows amplifiers which are designed for a high bias current (i.e., mostly Class A amplifiers) to be run at a lower bias, as an energy saving feature.  The low bias setting typically decreases the power consumption and heat output, with the penalty being a decreased output in Class A (before switching to Class AB to provide the rated total power output), and some associated level of sonic degradation (i.e., increased distortion).  In addition to the amplifiers mentioned, some (but not all) Clayton Class A amplifiers include high/low bias switches.