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Cascade switch superconducting nanowire single photon detectors has been fabricated of ultrathin NbN films deposited by DC-magnetron sputtering at room temperature on MgO substrates. Detectors using 4 to 24 nanowires in parallel, having an area coverage of 5times mum2 and a filling factor of 40%, have been investigated. Signal amplitudes increase with the number of parallel nanowires and reaches 12.3 mV with a signal noise of 20 muV. The range of bias currents where the detectors emit signal pulses also increase with the number of parallel nanowires and exceeds the nanowire critical current.