Maybe Ted Smith or Paul can explain what the difference is between DSD modulation and analog tape (AC bias frequency, about 100khz modulation).
Google AI notes:
Direct Stream Digital (DSD) modulation utilizes extremely high-frequency, 1-bit pulse-density modulation, with a standard sampling rate of 2.8224 MHz (64fs), which is 64 times the CD audio sampling rate. This high-speed sampling, often used for SACDs, enables a frequency response up to 100 kHz and a 120 dB dynamic range.
AC bias in analog tape recording is an inaudible, high-frequency signal (typically 40–150kHz) mixed with the audio during recording to overcome magnetic hysteresis, reduce distortion, and linearize tape response. It ensures high-fidelity, low-noise recordings by pushing the audio signal into the tape’s linear operating range, with settings calibrated to the specific tape formula
So both formats seem to modulate – or ‘‘ excite” – the signal to high-energy audio levels to chunk it into very fine “bits” .
I don’t think Red Book / PCM works this way. And neither does direct-to-disk lacquer.
Again, the folks behind Octave probably know much more!