text: The voltage pulses produced for every gamma ray that interacts within the detector volume are then analyzed by a multichannel analyzer (MCA). In the MCA, a pulse-shaping amplifier takes the transient voltage signal and reshapes it into a Gaussian or trapezoidal shape. From this shape, the signal is then converted into a digital form, using a fast analog-to-digital converter (ADC). In new systems with a very high-sampling-rate ADC, the analog-to-digital conversion can be performed without reshaping.
  Additional logic in the MCA then performs pulse-height analysis, sorting the pulses by their height into specific bins, or channels. Each channel represents a specific range of energy in the spectrum, the number of detected signals for each channel represents the spectral intensity of the radiation in this energy range. By changing the number of channels, it is possible to fine-tune the spectral resolution and sensitivity.
  The MCA can send its data to a computer, which stores, displays, and further analyzes the data. A variety of software packages are available from several manufacturers, and generally include spectrum analysis tools such as energy calibration (converting bins to energies), peak area and net area calculation, and resolution calculation.
  A USB sound card can serve as a cheap, consumer off-the-shelf ADC, a technique pioneered by Marek Dolleiser.  Specialized computer software performs pulse-height analysis on the digitized waveform, forming a complete MCA. Sound cards have high-speed but low-resolution (up to 192 kHz) ADC chips, allowing for reasonable quality for a low-to-medium count rate. The "sound card spectrometer" has been further refined in amateur and professional circles.