Most modern DACs (digital analog converters) have inside digital converter multibit PCM to 1-bit audio sigma delta modulation (a.k.a. DSD) and DSD to analog converter.
It allow to simplify DAC with keeping of quality.
Some DACs allow to send input DSD signal straight to internal DSD to analog converter.
However other DAC can receive PCM only.
AuI ConverteR 48x44 download free
1-bit audio signal very like to PCM in spectral area. Both contains audible signal in lowest part of spectrum (0 ... 20 kHz). After 20 kHz PCM have equal level noise for all frequencies. Sigma delta modulated signal have noise "hump" in ultrasound part of spectrum (upper 20 kHz).
Conversion DSF audio to PCM files (WAV, FLAC, AIFF, mp3,...) is digital filtration of 1-bit signal. After filtration noise "hump" eliminated. And remains only audible content. High DSD's sample rate adjusted to "low" PCM's sample rate.
About comparison PCM and DSD formats audio files here>>