QC by Studio B: manual

QC checks a mix before it goes to mastering, and a master against a reference track. Everything runs on your device, and nothing you load is uploaded or kept.

Switch modes with the pre-master / master switch at the top right of the faceplate. The manual key at the top left opens this page, and close takes you back to the device.

Pre-master: the pre-master checklist

Load a print

Drop your print on the screen, or press load print. QC reads WAV and AIFF only, at any bit depth and sample rate, because the grade is on the exact file. MP3 and other formats are refused, and the reason shows under the unit.

The screen lists each stage as it's measured, and a three-minute print takes a few seconds. remove print, at the top right of the screen, clears everything.

The screen

Waveform, at the top.

• The outline is the highest and lowest sample in each slice.
• The lighter body inside it is the loudness.
• Magenta marks anything past the −3 dBFS target line.
• Yellow ticks mark the spots the report found.
• Tap the waveform to hear 3.5 seconds from there.

Readout, underneath.

• The big number is the sample peak in dBFS, the reading the homework is graded on. The target is about −3 dBFS.
• Beside it are the true peak, the peak between samples in dBTP, and the typical peak, where most of the song peaks.
• The ladder shows the peak against the target, with each scale mark at its true position.
• While audio plays, a thin bar under the ladder shows the live peak.
• last print shows the previous print's peak, so a re-check shows the change. It is kept only until the page closes.

Controls

• find turns to the next spot the report found, or tap it to step forward. The screen marks the selected spot.
• play spot plays about 3.5 seconds around it.
• speakers only turns playback down. 100% is the file's own level.
• The level lamps show the verdict on the print level:
  • ok: the loudest peak is at or under −2.5 dBFS;
  • a little hot: above −2.5 dBFS;
  • too hot: above −2 dBFS.

Check lamps

Each lamp glows warm white while its check runs, then shows the verdict: green is ok, amber is check, red is fix. Tap a lamp to jump to its card in the report.

The report

The report lists the most urgent problems first. Each card has:

• What to do, in bold, first.
• Time keys. Tap one to hear that moment.
• The readings behind the verdict.
• why this matters, which opens the explanation.
• A spectrum analyzer, on the hum, below-hearing, mud, low-mids and sibilance cards. Violet is the whole song, cyan follows whatever is playing, and yellow is the move to make. Moves go on the tracks, never on the print. play the song starts playback right there.

Checks that pass are collected at the bottom under also checked, all clear. A print with nothing to fix gets the ready to hand in stamp.

Listen back

Plays the whole print behind the fractal window.

• position scrubs through the song.
• bloom shapes the picture: the mirror comes in first, then a spiral, then a tunnel.
• speakers matches the one on the main unit.

Master: the master, side by side

Load two files

• load master, or the top lane, takes your master, the file you'll deliver. It must be WAV or AIFF, so the numbers are exact.
• load reference, or the bottom lane, takes any audio file. MP3 and AAC are decoded on your device and marked as close, not exact.
• remove, on each lane, clears that file.

Listening

• A / B switches between your master and the reference instantly. Both play in sync, so nothing restarts.
• band lets you hear only the lows (below 250 Hz), the mids (250 Hz–4 kHz) or the highs (above 4 kHz).
• genre decides which loudness guidance you get:
  • loud: pop, rock, hip-hop;
  • quiet: jazz, folk, classical.
• mono folds both files to mono. Whatever sits at the edges of the mix should still be audible.
• match loudness, on by default, turns the louder file down so both play equally loud. Louder always sounds better at first; this takes that out of the comparison.
• speakers sets the volume.

The readings

Streaming services turn tracks up or down to a playback level. Spotify defaults to −14 LUFS, but listeners can change or switch off that setting, so QC doesn't aim for it. The genre sets the level; the −1 dBTP ceiling is the part that doesn't move.

The master report

• what stands out: one short reading each for loudness, against the reference, true peak, dynamics, balance, stereo and the mono fold-down.

• spectrum: both files' shapes at matched loudness, up to 16 kHz. The strip below shows which is louder where.
• low, mid, high: each band's share of the whole, A against B.
• loudness over time: short-term loudness for both files.
• stereo: correlation, side level and the mono fold-down, over the whole song and below 150 Hz.

Everything is a difference from the reference you chose, never an error.

Motion and accessibility

• Reduced Motion. Turn it on in your device's settings and every window holds still. Nothing flashes.
• Keyboard. Every control works from the keyboard. Knobs take arrow keys, and so do the position sliders.

Troubleshooting

• A file was refused. Pre-master prints and masters must be WAV or AIFF; export again in one of those.
• No sound on iPhone. Check the ring/silent switch and the volume.
• The page paused while measuring. Some hosts block the background worker, so QC measures on the page instead and pauses for a few seconds.
• Add to Home Screen isn't offered. The page must be opened from a web address, not from the Files app.