The Double-Decker Pre-Main Bus

This Friday tip has multiple applications-consider the following scenarios. You like to mix with mastering processors in the Main bus to approximate the eventual mastered sound, but ultimately, you want to add (or update) an unprocessed file for serious mastering in the Project page. However, reality checks are tough. When you disable the master bus processors so you can hear the unprocessed sound you'll be exporting, the level will usually change. So then you have to re-balance the levels, but you might not get them quite to where they were. And unfortunately, one of the biggest enemies of consistent mixing and mastering is varying monitoring levels. (Shameless plug alert: my book How to Create Compelling Mixes in Studio One, which is also available in Spanish, tells how to obtain consistent levels when mixing.)

Or, suppose you want to use the Tricomp or a similar maximizing program in the master bus. Although these can make a mix pop, there may be an unfair advantage if they make the music louder-after all, our brains tend to think that louder is better. The only way to get a realistic idea of how much difference the processor really makes is if you balance the processed and unprocessed levels so they're the same.

Or, maybe you use the cool Sonarworks program to flatten your headphone or speaker's response, so you can do more translatable mixes. But Sonarworks should be enabled only when monitoring; you don't want to export a file with a correction curve applied. Bypassing the Sonarworks plug-in when updating the Project page, or exporting a master file, is essential. But in the heat of the creative moment, you might forget to do that, and then need to re-export.

THE DOUBLE-DECKER, PRE-MAIN BUS SOLUTION The Pre-Main bus essentially doubles up the Main bus, to create an alternate destination for all your channels. The Pre-Main bus, whose output feeds the Main bus, serves as a sandbox for the Main bus. You can insert whatever processors you want into the Pre-Main bus for monitoring, without affecting what's ultimately exported from the Main bus.

Here's how it works.

Create a bus, and call it the Pre-Main bus.

In the Pre-Main bus's output field just above the pan slider, assign the bus output to the Main bus. If you don't see the output field, raise the channel's height until the output field appears.

Insert the Level Meter plug-in in the Main bus. We'll use this for LUFS level comparisons (check out the blog post Easy Level Matching, or the section on LUFS in my mixing book, as to why this matters).

Figure 1: The Pre-Main bus, outlined in white, has the Tricomp and Sonarworks plug-ins inserted. Note that all the channels have their outputs assigned to the Pre-Main bus.

Insert the mastering processors in the Pre-Main bus that you want to use while monitoring. Fig. 1 shows the Pre-Main bus with the Tricomp and Sonarworks plug-ins inserted.

Select all your channels. An easy way to do this is to click on the first channel in the Channel List, then shift+click on the last channel in the list. Or, click on the channel to the immediate left of the Main channel, and then shift+click on the first mixer channel.

With all channels selected, changing the output field for one channel changes the output field for all channels. Assign the outputs to the Main bus, play some music, and look at the Level Meter to check the LUFS reading.

Now assign the channel outputs to the Pre-Main bus. Again, observe the Level Meter in the Master bus. Adjust the Pre-Main bus's level for the best level match when switching the output fields between the Main and Pre-Main bus. By matching the levels, you can be sure you're listening to a fair comparison of the processed audio (the Pre-Main bus) and the unprocessed audio that will be exported from the Main bus.

The only caution is that when all your channels are selected, if you change a channel's fader, the faders for all the channels will change. Sometimes, this is a good thing-if you experience fader level creep while mixing, instead of lowering the master fader, you can lower the channel levels. But you also need to be careful not to reflexively adjust a channel's level, and end up adjusting all of them by mistake. Remember to click on the channel whose fader you want to adjust, before doing any editing.

Doubling up the Main bus can be really convenient when mixing-check it out when you want to audition processors in the master bus, but also, be able to do a quick reality check with the unprocessed sound to find out the difference any processors really make to the overall output.

Acknowledgement: Thanks to Steve Cook, who devised a similar technique to accommodate using Sonarworks in Cakewalk, for providing the inspiration for this post.

LINK:	https://blog.presonus.com/index.php/2020/04/17/double-decker-pre-main-...
	See more stories from presonus

More from PreSonus