This article aims to explain the differences between the previous and the new Virtual Console Collection Metering and the path that led us to this solution.
The VCC is a group of saturation modules for VMR. Each console has its own Clip Threshold.
When the input is below this threshold, the signal is inside the Non-Clipping Zone, meaning that there is no clipping nor extra saturation involved.
When the input is above the threshold, the algorithm starts clipping, which means more saturation and more audio artifacts and non-linearities.
It's important to understand that the Clip Threshold and the Meter Calibration are two completely different and unrelated things; the Clip Threshold is the point where the console will stop acting linearly, whereas the Meter Calibration is the dBFS Peak audio level for a sine wave at 1kHz that would read 0VU. Changing the Meter Calibration doesn't change anything in the algorithm, hence in the sound.
Previous VCC Metering
The previous VCC Metering shows the output level. The meter is calibrated to display 0VU when being fed by a sine wave at 1kHz at Calibration dBFs Peak.
Issue with this Metering
Each VMR module's VU meters have to give an indication of what the module does.
For instance, the Trimmer is a gain module, so the meter displays the signal after the gain stage; the 116 is a compressor, so the meter displays the actual gain reduction.
Consequently, the VCC is a saturation module, so the meter should allow us to easily visualize where the signal is within the algorithm range, i.e. below or above the Clip Threshold.
Therefore the previous VCC Metering doesn't make sense because displaying the output level doesn't give any information of the signal's saturation.
New VCC Metering
An appropriate fix would be for the meter to display the input level, but this wouldn't allow us to know what's happening in the console model. We would probably read +2VU when the algorithm is actually clipping the signal at -1VU, it's not coherent.
Consequently, we settled for two changes:
First, we moved the metering point just before the output stage:
This way, the meter displays what's going on after the console. That makes sense because you can now read where you are within the algorithm range, and the level you read matches exactly what you will be getting at output, without your make-up gain.
Secondly, we added a Clip-LED. The Clip-LED lights as soon as the signal gets above the Clip Threshold. The Clip-LED Threshold is console dependent, because each console has a different Clip Threshold.
Thanks to those two things, you can now easily visualize how the signal behaves in the console: Clip-LED off, your signal doesn't clip the console; Clip-LED lit, the signal has exceeded the Saturation Threshold.