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7.2.6. Adjusting Recording Level (Volume)

It is important to properly set the level of the inputs betfore recording.
The nature of audio equipment is such that it can only perceive sound pressures (perceived as volume) within a certain range. If a sound is too quiet, it will not be perceived, and if it is too loud, it will not be perceived accurately. Furthermore, and this is most important when thinking about your own ears — if a sound is far too loud, it may permanently damage the audio instrument.
The nature of digital audio is such that there is a distinct number of volume levels at which something can be recorded. If a sound is either below or above that range, then it will not be correctly recorded. When such an improperly-recorded sound is played back, whether too quite or too loud, humans will usually perceive it as "nothing but noise."
When Ardour records silence, it behaves no differently from when there is no input at all. When Ardour calculates that a portion of audio is too loud and therefore distorted, it outlines the wave-form representation in red, as shown in Figure 7.5, “Audio that is too loud”.
Audio that is too loud
A waveform in Ardour, showing red peaks where the audio is too loud.
Figure 7.5. Audio that is too loud

There are three simple strategies that can be used to change the input level of an audio signal:
  1. Move the microphone closer or farther from the source
  2. Route the microphone through a mixer before it reaches the audio interface
  3. Route the audio through a bus in Ardour before it gets recorded
Here are the advantages and disadvantages of each approach:
There are some circumstances where it is either impractical, impossible, or not advisable to move the microphone or route it through a hardware mixer. In these cases, you can use a bus in Ardour to modify the volume of the input signal before it is recorded.
  1. Choose TrackAdd Track/Bus.
  2. Select "busses" in the window that pops up.
  3. Choose the number of busses that you wish to add. You need one for every track that you are recording, and of which you want to adjust the volume. It is also possible to record at several different volumes.
  4. Set the number of channels that youw ant int he bus.
  5. Once you have the new bus, change its name by doing whatever. I suggest naming it something that makes it obvious you are using the bus for recording, rather than exporting, like "REC-Bus."
  6. Ardour automatically sets up busses to be used with audio being outputted. Furthermore, the volume/level control only works on audio beign outputted from a track or bus. This is why you cannot use the track's volume/level control to adjust the input volume for that track.
  7. Use QjackCtl to reconnect like this (for help, refer to Section 7.2.9, “Routing Audio and Managing JACK Connections”):
    1. Disconnect all of the connections to/from the bus you want to use for recording ("recording bus").
    2. Ensure that nothing is connected to the input of the track onto which you want to record ("recording track").
    3. Connect the microphone (the input source) to the recording bus' input
    4. Connect the input bus' output to the recording track's input.
    5. Ensure that the recording track's output is connected to the "master" input (this is the master output bus, which should be present in all projects, and through which all output audio should be routed).
Remember: only one track-to-be-recorded can be routed through a bus for this purpose, because a bus can only output one stream of audio.
Here is an algorithm to test whether your tracks are set at a good recording volume. This should be done before arming any tracks for recording. Unfortunately, you can never know that you have chosen the best input level until after a region is recorded. It takes both instinct and experience to be able to choose good input levels reliably.
  1. Set up all microphones as required.
  2. Set up connections in JACK as required.
  3. Set up any recording busses as required (see above).
  4. On the audio tracks being recorded, set the "metering point" to "input" (here's how to do that).
  5. Ask the performers to demonstrate the loudest passages they will be doing in the session. Adjust the input level so that the maximum level falls between -3 dB and -6 dB (by looking here). You can reset the maximum-level-seer by clicking on it.
  6. Ask the performers to demonstrate the quietest passages they will be performing in the session. Adjust the input level so that this does not fall below -40 dB; it should probably be between -30 dB and -20 dB.
  7. Ask the performers to demonstrate an average passage from what they will be performing in the session. This is usually less important than the previous two checks, but if most of the performance will be quieter, it may be worth risking a higher input level in order to capture more detail. Nevertheless, a "moderate" volume level should result in and input level reading of -20 dB to -10 dB.
  8. When you are more experience both with the kind of group you are recording, and the software and equipment being used to do it, you may not need to do these level-checks every time. It's better to be safe than sorry, however, because once a musical moment has passed, it is impossible to re-create.