As a musician it is highly recommended that you use 24 bit resolution in your digital audio workstation. This affords a number of real advantages and not just when processing the audio with plug in software. When you set your DAW to 24 bit you have allowed yourself to record at a much lower level without any technical detriment. The theoretical noise floor at 24 bit is significantly lower than that of a 16bit recording. This means that you can now record signals that peak at around -18dBFS. Thats sounds low but in fact this is equivalent to the electrical level that would have been understood as nominal in a large NEVE or SSL console i.e. 0Vu. In a digital system -18dBFS is referenced to +4dBu (1.23 volts), the same can be said of 0Vu. So there is no need to record at high recording levels when using 24 resolution. I think the confusion may have crept in for 2 reasons, we we recommended that hot signals were good at 16 bit and also the saying “hit zero” may have worked it’s way into the minds of musicians as a hang over from the days of large consoles and Vu metering.
Now we can consider mixing headroom on your master output bus. As with recording at 24 bit there is no need to peak so high on the outputs. Simply use a “peaky” signal to reference against. When you start you mix use a kick drum or snare as a reference to built the mix around. Peak the signal at -18dBFS on your stereo output meter. Once you have started mixing other instruments try not to adjust the level of this reference and build the mix around it. This will have built in plenty of headroom and you should not have any issues with peaking above 0dBFS.
Another bonus is going to be cleaner monitoring, this is because the small electronic devices in your sound card will no longer be operating as close to their technical design limits. This means less distortion should be present in the signal monitored. Low cost, aged design op amps have a habit of increasing their THD as they get closer to their maximum amplification capabilities. The only thing you need to do when working at -18dBFS is to raise your monitoring volume on your amplifier or monitor controller to compensate for the lower operating level.
Many pople will put a limiter on the master bus to keep the levels up and at the same time from going over digital zero. However, this is an extreme dynamic process and will quite possibly negatively influence your mix decisions. Your drum peaks will be arrested in their prime. This is where the punch of the mix resides. Instead if you require a limiter later in self finalizing you can export your mix at 24 bit and limit in a new project on the stereo file. Self finalizing or professional online mastering is best done in a separate project with fresh ears. This lower operating level has many benefits for musicians and is a great way to end up with better, cleaner sounding mixes.
Barry Gardner is the chief mastering engineer at SafeandSound online mastering