Preparing the Mix for Mastering

A master is only as good as the file it starts from. Most problems that end up "unfixable" in mastering were created during the bounce: a limiter left on the master bus, a mix clipped into the red, an MP3 exported by mistake. Ten minutes of preparation avoids all of them.

Leave headroom

Headroom is the space between your mix's loudest peak and 0 dBFS, the digital ceiling. Mastering needs that space for EQ boosts and gain changes that would otherwise clip.

Aim for mix peaks somewhere around −6 to −3 dBFS. The exact number matters much less than people think — in a 24-bit or 32-bit float file, a mix peaking at −6 dBFS has lost nothing compared with one peaking at −1 dBFS. What matters is:

• No clipping anywhere. Check the master meter during the loudest section. If it ever hits 0 dBFS in a fixed-point file, those peaks are flattened permanently.
• Get headroom by pulling faders down, not by adding a limiter. Lower all the track faders together (or put a gain stage before the master's processing) so your mix balance and any bus compression behave the same.

Don't worry about the mix being "too quiet". Loudness is the mastering stage's job.

Take the limiter off the master bus

Many producers mix with a limiter on the master to hear the song "loud". That's fine while mixing, but bounce the mastering file without it. A limiter that's already squashing peaks:

• Removes the transients the mastering compressor and limiter need to react to.
• Locks in distortion you can't undo.
• Leaves nothing for the final limiter to do except make things worse.

Bus compression is different. If you mixed into a gentle glue compressor on the master (a couple of dB of gain reduction) and the mix depends on it, keep it — the balance you approved includes it. Just make sure it isn't clipping, and tell the person mastering (or remind yourself) that it's there.

A good habit is to bounce two versions: the mix as you've been hearing it, and the mix with no master-bus processing at all. Master whichever sounds better once both are level-matched.

Clean up the edges

• Start and end. Trim silence to a few hundred milliseconds before the first sound. Let the tail decay fully — a reverb cut off abruptly is very audible on headphones. Fades can be done at mastering, so leave some room.
• Count-ins and clicks. Mute the metronome and any count-in. Listen to the first and last seconds in solo; that's where stray noises hide.
• Mono compatibility. Sum the mix to mono briefly. If an instrument disappears or the low end collapses, fix that in the mix now.

Choose the right file

Export a lossless file: WAV or AIFF.

• Bit depth: 24-bit or 32-bit float. Both give far more dynamic range than you need, so quiet passages and fade-outs stay clean. 32-bit float also can't clip on export, which removes one way to ruin the file. Don't export 16-bit at this stage — the conversion to 16-bit happens once, at the very end, with dither.
• Sample rate: keep the session's rate. If the project runs at 48 kHz, export at 48 kHz; if it's 44.1 kHz, export at 44.1 kHz. Converting sample rates during mixdown adds a processing step for no benefit. Any conversion needed for delivery happens at the end of mastering.
• Never an MP3 or AAC. A lossy file has already thrown away information, and every lossy-to-lossy conversion adds artifacts.

Write down what the master needs to know

A short note saves you guessing later:

• Tempo and key, and the song's title as it should appear on release.
• Where the loudest section is, so you can check limiting there.
• Any intentional quirks ("the distorted intro is deliberate", "vocal is meant to be dry").
• Whether this is a single or part of a larger release — the album context changes the target level.

A pre-mastering checklist

1. Peaks below about −3 dBFS, no clipping.
2. No limiter on the master bus; bus compression kept only if the mix depends on it.
3. Silence trimmed, tails intact, no clicks or count-ins.
4. Mono check passed.
5. 24-bit or 32-bit float WAV/AIFF at the session sample rate.