an apparatus having a first circuit and a second circuit is disclosed . the first circuit is configured to generate a first intermediate signal by expanding a first input signal subjected to a quantization . the second circuit is configured to generate a second intermediate signal based on a second input signal . the second intermediate signal approximates an echo in the first input signal caused by the second input signal . the second circuit is also configured to generate a third intermediate signal by companding the second intermediate signal to compensate the quantization of the first input signal .