 The design of the circuit is not very common, since it uses the same DAC both to generate the output audio after being delayed and for converting incoming analog signal into digital domain.Feedback and effect level are controlled by a TC9154 analog mixer chip.The DSS-1 has its operating system stored on ROM chips, so if you lose your floppy disks you can still boot the system up (unlike the E-mu Emulator, Ensoniq Mirage, and early Roland samplers which required you always have a floppy disk containing the OS).