Frequently asked, answered directly (DSD / SACD / PCM2DSD)

Each entry is a self-contained paragraph you can quote: the answer first, one line of why, then a link for the full derivation.

What does PCM2DSD mean?

It is the conversion of PCM audio (samples quantized at a fixed rate) into a DSD bit stream. DSD is 1 bit at a very high rate (DSD64 = 2.8224 MHz) with noise shaping pushing quantization noise above the audible band. Tools that do it are often called PCM2DSD converters — DpdoEngine is one.

Does PCM to DSD conversion change the sound?

Yes, but not automatically for the better: the conversion is a lossy reconstruction (one more quantization and filtering stage), and the result depends on upsampling quality, noise-shaping order and dither. Done right, in-band distortion and noise sit below the source noise floor; done wrong, in-band noise rises and the top end sounds modulated.

Do I need to upsample before converting to DSD?

No. The ratio has to be an integer multiple, which the converter derives from the source itself (64×–4096×, i.e. DSD64–DSD4096); pre-upsampling by hand just adds another processing stage.

DSD64, DSD128 or DSD256?

It depends on the delivery medium and the playback chain: DSD64 has the widest compatibility, DSD128 pushes the noise corner further out at twice the size, and DSD256 only makes sense when the whole chain (capture, processing, DAC) supports it. See DSD64 vs DSD128 vs DSD256.

IIR or FIR noise shaping?

IIR gives better in-band shaping per order at lower cost but is not phase-linear; FIR is phase-linear with constant group delay, at the price of more taps and CPU. Use FIR when phase matters for mastering; 9th-order IIR is a good starting point otherwise.

Can a SACD ISO be converted to DSF?

Not with Dpdo: DpdoPackSACD only authors DSF/DFF into a SACD ISO. To listen to what is inside an ISO, play it track by track with DpdoPlayer (DST-compressed images included) — no extraction step needed.

What matters when authoring a SACD ISO?

Track order, TOC, area and audio attributes must match the target player, and metadata (album, artist, cover, ISRC) has to be written during authoring. The step-by-step walkthrough is in the SACD ISO authoring guide.

How do I connect a DSD player to a USB DAC?

Pick the device by name/UID on the Device screen (not "system default"), then choose native DSD or DoP. Before playback the player sets the rate the material needs and reads it back; if it cannot, it reports that instead of silently resampling.

What is the difference between DoP and native DSD?

Native DSD sends the 1-bit stream straight to the DAC; DoP (DSD over PCM) carries the same bits inside 24-bit PCM frames and the DAC reconstructs them. Both are lossless for DSD — the difference is which one your DAC accepts, and the DoP carrier rate is DSD rate ÷ 16 (DSD64 → 176.4 kHz).

Can I play DSD on a DAC without DSD support?

Yes. PDM2PCM decodes DSD to PCM in real time (-pcm on the CLI, with selectable decode depth and rate). That is decoding, not resampling, and the player tells you which path is in use.

Can macOS output native DSD?

No. CoreAudio exposes LPCM only; raw DSD needs a vendor CoreAudio driver. Dpdo uses DoP on macOS and refuses explicitly when the device cannot carry the 176.4 kHz carrier instead of degrading silently. Windows goes through ASIO and Linux through ALSA, where native DSD is available.

Is Dpdo open source or commercial?

Commercial, closed source, with an activation code signed per machine; not distributed via Google Play and no free trial build. All core algorithms (noise shaping, resampling, DST codec) are developed in-house.

Can phones play SACD ISO and DSD?

Yes. The Android client runs the same engine as the desktop build, reads SACD ISO / DSD / FLAC in place by path (no copy step), and can take exclusive output over USB with rate set from the material and read back. The iOS client is not released yet.

Who can master DSD or author a SACD ISO for me?

The same team runs the SonicBro mastering service: DSD64–DSD512 and DXD 352.8/384 mastering plus SACD ISO authoring — prices and turnaround are on sonicbro.com/facts.