An object inspection system, comprising: a transmit and receive section to generate a test signal and to receive a responsive echo signal; a transducer configured to convert the test signal to an ultrasonic signal, to apply the ultrasonic signal to a target object to be tested, to receive an ultrasonic echo signal and to produce the echo signal for the transmit and receive section; a signal processing circuit coupled with the transmit and receive section for receiving and processing the echo signal, the signal processing circuit including at least two signal processing channels (19a, 19b), each channel scaling the echo signal to a different degree, and each channel having a respective first and second analog to digital converter (132, 134); and a selection circuit configured to select that output of that analog to digital converter which provides the largest amplification of the echo signal without having overflowed, and a first one of said signal processing channels being coupled directly to the echo signal, characterized in that the first one of said signal processing channels comprises a respective preamplifier and a respective clamping circuit for preventing said preamplifier from becoming saturated, and a second one of said signal processing channels is coupled directly to the echo signal and comprises a respective preamplifier and a respective clamping circuit to prevent saturation of the preamplifier of the second one of said signal processing channels, the clamping circuit of the second signal processing channel being configured to maintain a constant input impedance on the echo signal, at least up to a signal level of said echo signal which equals a maximum input range to the preamplifier of the first one of said signal processing channels. a transmit and receive section to generate a test signal and to receive a responsive echo signal; a transducer configured to convert the test signal to an ultrasonic signal, to apply the ultrasonic signal to a target object to be tested, to receive an ultrasonic echo signal and to produce the echo signal for the transmit and receive section; a signal processing circuit coupled with the transmit and receive section for receiving and processing the echo signal, the signal processing circuit including at least two signal processing channels (19a, 19b), each channel scaling the echo signal to a different degree, and each channel having a respective first and second analog to digital converter (132, 134); and a selection circuit configured to select that output of that analog to digital converter which provides the largest amplification of the echo signal without having overflowed, and a first one of said signal processing channels being coupled directly to the echo signal, characterized in that the first one of said signal processing channels comprises a respective preamplifier and a respective clamping circuit for preventing said preamplifier from becoming saturated, and a second one of said signal processing channels is coupled directly to the echo signal and comprises a respective preamplifier and a respective clamping circuit to prevent saturation of the preamplifier of the second one of said signal processing channels, the clamping circuit of the second signal processing channel being configured to maintain a constant input impedance on the echo signal, at least up to a signal level of said echo signal which equals a maximum input range to the preamplifier of the first one of said signal processing channels.