The analog signals provided by a seismic-velocity well logger, resulting from the transmission of seismic impulses from a transmitter to a receiver in a logging sonde in a well by paths that include travel through the rock walls of the borehole, are digitally recorded. These seismic impulses and the resulting received seismic signals, or traces, are repeated approximately 20 times per second. The recording apparatus digitizes these analog traces by determining signal amplitudes at intervals of approximately 10 microseconds and temporarily stores the digital values. The apparatus includes a programmable-gain amplifier, an analog-to-digital converter, a computer, and a memory in which are, in addition to the data, also stored the values of gain which are to be used in digitizing the next signal. That is, on each digitizing interval a stored gain "program" is read out of the computer and sets the gain of the amplifier. Besides transferring the stored data to a standard computer input tape, a digital-to-analog converter and a scope are provided for displaying the successive values of gain and digitized signal, for monitoring the operation of the apparatus.