The NAAD LD4 is based on an ARM Cortex-M4F (STM32F407 168 MHz) MCU, the firmware is open source. The module is digital but it is not just playing samples, but uses the processor to generate four sound engines as drumsynthesizer. A frequency and amplitude modulated oscillator, with pitch-envelope is mixed with noise and finally bended thru a filter., an LFO can modulate the cutoff frequency and thats it? To generate some smart drumsounds this is absolutely fine as plenty of classic machines has showed us in the past already. And also some tonal sounds can be created this way quite easy and fast.
36 TE Eurorack module