How to actually verify your DAC is doing what it claims

Something I get asked a version of constantly: how do you know your DAC is running the rate and bit depth you think it is, instead of your player parroting back whatever the OS told it?

Cheapest self-check, no app involved, run it on your own library tonight: flac -t a few files. If it reports the MD5 signature is unset, that file can't vouch for its own decoded contents. Plenty ship that way, and paid downloads aren't exempt. It turns up in bug reports against store files. FLAC's hash covers the decoded audio, not the file bytes, so re-tagging or a recompress at another level leaves it alone. An unset one just gives you nothing to check against.

That's the file level. The chain level is worse: even a file that passes tells you nothing about what actually reached the DAC. The badge on your now-playing screen is a claim the app makes about itself, not a receipt. Mine included, and I build it.

Obviously I'm biased. What Meringo does about it: arm Verified Capture (Settings → Audio Diagnostics) and it hashes every byte it hands to the USB isochronous pipe (the wire format after decode, a different hash answering a different question than FLAC's). Then it re-decodes the same file, lays the PCM out identically, and hashes that copy too. Matching hashes mean nothing touched a bit between file and pipe: no resample, no requantize, no EQ, no ReplayGain. One off the registry: Qudelix 5K, 96 kHz/24-bit, build 1.28.5 (124), cb459147…295adf. The checker script at meringo.app/verify shares no code with Meringo, so you don't have to take my math on faith.

The limit, and it matters: isochronous USB carries no delivery acknowledgement. No software on any platform can prove what the DAC received, only what got put on the wire for it. Anyone telling you their chain is "proven bit-perfect end to end" is skipping that part.

A capture that lands on NOT BIT-IDENTICAL or INCONCLUSIVE is worth having too. The registry publishes those verdicts alongside the clean ones.

Sub's been quiet a couple months — that's on me, I was heads-down on 1.32.0. So: if you've got a Tuning Vault profile worth sharing, or your DAC does something weird under capture, post it. I read everything in here.