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Setting input levels
When recording digital sound, it's important to set the input levels correctly - loud enough to ensure low noise and high audio quality, but not so loud that clipping (digital distortion) occurs. When you record, clipping can occur in two places in the signal path:
In the audio hardware, when an analog input signal is converted to digital format.
If the analog signal is too loud, it cannot be represented properly in a digital format (there will be no headroom). The result is clipping.
When the audio signal is written to an audio file after passing through the input busses.
Since you can adjust levels, add EQ or effects in the input busses, it's possible to make the signal too loud at that stage. Again, the result will be clipping.
For this reason, you may need to check the input levels "in two steps":
Checking the signal level coming into the audio hardware
To check the level of the "unprocessed" signal coming into the audio hardware you need to switch the level meters to "Input VU". In this mode the input channel level meters will show the level of the signal at the input of the bus, before any adjustments such as input gain, EQ, effects, level or pan:
1. Right-click in the Mixer window.
The Mixer context menu appears.
2. Select the VU-Meter Settings submenu and make sure "Input VU" is activated.
3. Play back the audio and check the level meter for the input channel.
The signal should be as loud as possible without exceeding 0 dB (the Clipping indicator for the input bus should not light up).
The Clipping indicator.
4. If necessary, adjust the input level in one of the following ways:
Adjust the output level of the sound source or external mixer.
Use the audio hardware's own application program to set the input levels, if this possibility is provided.
See the documentation for the audio hardware.
If your audio hardware supports the ASIO Control Panel function, it may be possible to make input level settings.
To open the ASIO control panel, open the Device Setup dialog on the Devices menu and click the Control Panel button on the Setup tab for the VST Multitrack device.
Instead of switching the level meter mode you can add an extra input bus using the same audio inputs (see The VST Connections window) and use this bus solely as a signal level meter (with "Post-Fader VU" mode always selected). This bus should then always be "zeroed" (gain and level set to 0.0 dB, no effects or EQ added) to show the level of the input signal.
Checking the signal level after the input bus
Internally, Nuendo processes audio at 32 bit float resolution, which makes it virtually impossible for clipping to occur. However, when the signal is written to a file on disk clipping can occur, depending on the selected record format (bit depth):
If you record in 32 bit float format the bit depth will not be reduced - which means there's no risk of clipping at this stage.
Also, this preserves the signal quality perfectly. Therefore, you should consider using 32 bit float format when you are recording with effects (see Recording with effects).
If you record in 16 or 24 bit format the available headroom is lower which means clipping can occur if the signal is too loud.
To avoid this, set the signal level in the following way:
1. Bring up the mixer context menu and select "Post-Fader VU" from the VU-Meter Settings submenu.
2. Set up the input channel, adding EQ and/or effects as desired.
With some effects you may want to adjust the level of the signal going into the effect - use the Input Gain knob for this (note that you need to press [Shift] or [Alt] to adjust the Input Gain).
3. Play back the audio and check the level meter of the input channel.
The signal should be as loud as possible without exceeding 0 dB (the Clipping indicator for the input bus should not light up).
4. If necessary, use the input channel fader to adjust the signal level.
