The pre-master is a stage dealt with by primarily the mixing engineer. This pre-master stage is a buffer for the mastering engineer to be able to work effectively and efficiently by taking care of a few important things. Some pre-master methods are often carried out by the mastering engineer, however, they’ll typically charge extra.
Some pre-master methods include;
1. Roll off filters
Frequency content can often be produced by various methods of processing and need to be removed before mastering can take place. Using a high pass filter at 30Hz and a low pass filter at 19kHz will ensure a controlled frequency spectrum.
In the analog days, a minimum allowable headroom became standard practice when progressing from mixing to the mastering stage. This was to compensate for the way analog recording and metering differs from digital. In any case, the practice is still to this day followed through with. The headroom required by mastering engineers is between -3 and -6dBFS. Anywhere within this range is enough headroom for the mastering engineer to work with and bring out the best the track.
3. Export information
When exporting a mix for mastering, do not normalize on export and do not apply dithering. This is for AFTER mastering has been applied. When using samples with a uniform sample rate and bit depth, maintain the same on export. If you are using 16 bit samples, selecting a higher bit rate such as 24 will not increase quality. If you are using 16 bit AND 24 bit samples, select the higher bit rate to compensate for those higher quality samples or else those 24-bit files will be crunched down to a lower quality 16-bit version.