A key part of Mössbauer (MB) spectroscopy is the selection of the resonant energy range out of a detected γ-ray spectrum. As the detection of the entire γ-ray source spectrum generates high count rates, selection of the photons having the MB transition energy requires fast processing. To achieve this goal with the MIMOS II instrument, developed and built by the group of Göstar Klingelhöfer at the TU Darmstadt and JOGU Mainz, multiple sets of two comparator units, using fast operational amplifiers to define a certain energy window, are implemented in the instrument’s main electronics board. These analogue circuits use stabilized reference voltages to set the thresholds. Today’s fast microcontroller based analogue-to-digital converters (ADC), such as the Arduino Due, show better signal to noise ratio and possibilities for a two-dimensional extension of Mössbauer spectroscopy.