A mass spectrometer having a secondary electron multiplier for multiplying ion current-triggered secondary electron currents in a series of discrete dynode stages, comprising: - a voltage supply circuit for each dynode stage, each being configured to supply a substantially non-variable voltage to the corresponding dynode stage when active; - a feedback control circuit, which has no DC path to ground, configured to divide the series of discrete dynode stages into a first subrange of active dynode stages and a second subsequent subrange of passive dynode stages, where the first and second subranges together make up the total series of discrete dynode stages, thereby being able to change a multiplier gain as a function of a number of active dynode stages in the first subrange and as a function of a last measured ion signal; and - a single trans-impedance amplifier and a single analog-to-digital converter, measuring a secondary electron output current of a last active dynode stage in the first subrange; wherein the first subrange of active dynode stages is configured to operate with secondary electron multiplication and the second subrange of passive dynode stages is configured to be de-energized and short-cut, short-cutting a line from one dynode stage to the next; wherein the voltage supply circuits supplying voltage to said passive dynode stages are configured to be de-energized and short-cut, feedback controlled by a data output of the analog-to-digital converter; and wherein the variable series of short-cuts forming said line is configured to guide the secondary electron output current of the last active dynode stage in the first subrange to the trans-impedance amplifier. - a voltage supply circuit for each dynode stage, each being configured to supply a substantially non-variable voltage to the corresponding dynode stage when active; - a feedback control circuit, which has no DC path to ground, configured to divide the series of discrete dynode stages into a first subrange of active dynode stages and a second subsequent subrange of passive dynode stages, where the first and second subranges together make up the total series of discrete dynode stages, thereby being able to change a multiplier gain as a function of a number of active dynode stages in the first subrange and as a function of a last measured ion signal; and - a single trans-impedance amplifier and a single analog-to-digital converter, measuring a secondary electron output current of a last active dynode stage in the first subrange; wherein the first subrange of active dynode stages is configured to operate with secondary electron multiplication and the second subrange of passive dynode stages is configured to be de-energized and short-cut, short-cutting a line from one dynode stage to the next; wherein the voltage supply circuits supplying voltage to said passive dynode stages are configured to be de-energized and short-cut, feedback controlled by a data output of the analog-to-digital converter; and wherein the variable series of short-cuts forming said line is configured to guide the secondary electron output current of the last active dynode stage in the first subrange to the trans-impedance amplifier.