The idea that a lossless compressed file and an uncompressed file should sound identical is perfectly logical — and sometimes, in practice, it might not hold.
FLAC and WAV are both lossless formats. FLAC is compressed, WAV is not, but the audio data in each is mathematically identical when decoded. In theory, with a perfect playback chain, they'd be indistinguishable. But here's what a lot of us in the HiFi Family have noticed: they can sometimes sound different. The WAV can seem a little more open, a touch more resolved, slightly more three-dimensional. Is this always audible? No. Does it depend on the system? Almost certainly.
But once you hear it on a resolving chain, it tends to stick with you.
The reason probably isn't magic. It might be a sensitivity to how hard the hardware is working. Decoding a FLAC file requires real-time decompression — the processor runs an algorithm, manages memory, and hands the decoded data off to the playback engine while keeping the audio buffer fed. That activity doesn't happen in a vacuum. It can generate noise, heat, and tiny fluctuations in the power supply and ground plane. None of those things are large. But in a resolving system, they are audible.
What this might really illustrate is something we keep running into in audio: the digital domain isn't necessarily immune to analog contamination. Every piece of digital gear has an analog substrate — power supplies, clocks, ground planes — and that substrate can affect sound in ways that don't show up in a bit-perfect checksum.
The data gets through intact. Everything else is still fair game.
The PMG 512 DAC was designed with exactly this in mind, keeping the digital and analog domains aggressively isolated so that what reaches the conversion stage is as clean as we can make it.
The point of this post is simple: everything in our system affects everything else.
Focusing on the mystery of how two bit perfect formats can sound different is a bit like scratching one's head over why two identical recipes taste different. It's all in the execution.
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