Abstract: The compression portion of an instantaneous companding (compressing-expanding) system includes at least two and preferably four "bi-gain" amplifiers connected in cascade. Each bi-gain amplifier normally has a low-gain state and can be switched to a discrete high-gain state. A discrete reference voltage is provided to compare with the output of each amplifier. The amplifiers are initially switched to their low-gain states and the reference voltage corresponding to the first amplifier is selected. A comparator means makes a comparison between the system's output voltage and the selected reference voltage. The control means switches the first amplifier to its high-gain state or holds it in the low-gain state depending on the result of the comparison. By utilizing a different variable reference voltage and bi-gain amplifiers with two different amplification factors, the number of amplifiers and comparisons is significantly reduced.