The first question I got about my mixing and mastering blog is about gain staging, so here goes…
Don’t use your peak meter for gain staging.
In the digital realm the focus has been on peaks too much, that’s because 0dBFS (FS = Full Scale, 0dBFS = maximum loudness of digital sound) and higher distorts while 16bit processing requires the highest level of audio possible to keep the audio far above the noise floor and digital distortion.
Plugins, especially plugins that emulate hardware, are not designed for audio that’s really loud. Even if your peaks are below -3dBFS before processing, your audio will usually come out worse after processing. So just record in 24bit, it has a wider dynamic range, the noise floor and digital distortion will stay low while processing. Digital processing has improved, your noise will be lower then in the analog days, even when peaks are below -12dBFS.
Measuring peaks is only necessary to avoid clipping. Peaks say nothing about loudness, they are gone quickly, just causing tiny ripples. Some instruments can have peaks around -8dBFS and still sound softer then instruments with peaks around -18dBFS. It’s what’s around the peaks that matters, so what you need is a meter that measures more average loudness.
VU meters (VU for Volume Unit) were designed for that in 1942. It takes 300ms for them to rise to the loudness level of your signal and 300ms to fall. VU meters are often added to recording equipment so you get the right loudness from the start. Different VU meters give slightly different results but that’s okay I guess. VU meters are usually calibrated at -18dBFS, meaning a test tone of -18dBFS will show as 0dBVU on a VU meter. That leaves 18dB of headroom for peaks! Peaks rarely go to 0dBFS if dBVU = 0, but VU meters need clipping indicators just in case.
Here’s how you can gain stage: put a gain plugin in the first slot of your channel. If your DAW doesn’t have a gain plugin, Blue Cat Audio provides one for free.
Put a VU meter in the second slot. I use Klanghelm VUMT or HoRNet VU Meter. The main advantage of the HoRNet VU Meter is that you can play a whole track and it will set the gain right for you. On my system it’s less reliable though, I often get different results. Klanghelm VUMT gives the same result every time but it doesn’t have a memory for the duration of a whole track. If you click on the led light, VUMT will show maximum dBVU values for about 2 seconds after they happen on the left of the led light.
Loop the loudest part of your track. If the maximum dBVU level goes above zero, reduce the gain with the same amount. If you want a hotter signal, for more saturation and distortion in plugins that emulate analog hardware, you can allow maximum values of +3dB. It’s easy to overdo that though. You can tweak the gain in VUMT or let the HoRNet meter do it by itself. Try again. If the VU meter doesn’t go above the desired level and doesn’t clip, you’re probably done. Set the gain plugin at the same amount as the VU plugin and set the gain in the VU plugin back to zero. Run the whole track just in case you picked the wrong part and adjust the gain setting if needed. You can remove the VU meter, it’s set-and-forget.
What you can also do, is automate the gain plugin to adjust the loudness per segment. Sometimes you want some segments to be louder or softer then others and sometimes it’s the other way around: segments are too loud or too soft and you want them as loud as the others. You can loop each segment, set the gain of each segment to your liking and check if the VU level doesn’t go above your desired level.
You can use gain staging for Virtual Instruments like you would set the input gain of your hardware before you start recording. Virtual Instruments are often programmed too loud, which results in audio that’s too hot when you’re arranging. Turning the fader down 12dB will still make plugins clip and ruin your bounces, so it’s best to gain stage the instrument before you add it to the arrangement.
I created a short midi file that you can download at the end of this blog. It triggers 88 notes twice at maximum velocity. It starts with all 8 A’s, B-flats, etcetera, then single notes chromatically. If the instrument is not full range and has key switches, disable or delete the notes in the midi file that are out of range first. You can play this file with a VU meter added to the channel and tweak the output level of the virtual instrument until it doesn’t go above 0dBVU. Then you can save the instrument or the channel in the folder structure that I described in my blog “the best way to organize your presets”. When you’re done with the arrangement you can gain stage again before bouncing the instrument to audio to get optimal loudness.
That’s all for now. If you’ve got questions, post them here!
Download this guide and the midi file in rtf format: