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Aura8ip / Jan 2012
A u r a 8 i p P r o G U I
Metering Discussion
Input Metering
All metering in the Aura8ip is sample-accurate, true peak reading, includ-
ing the gain reduction meters. The Input and Output meters are calibrated
in dBFS so that an accurate determination of these levels may be made. The
recommended input level operating range is between -18dBFS and -12dBFS.
Care should be taken to ensure that the input peak level never exceeds -9dBFS,
especially if the Phase Rotator is enabled. This is because clipped waveforms
exit any phase rotator at much higher peak levels because the phase rotator
upsets the signal’s harmonics. It is not uncommon to see clipped waveforms
exit a phase rotator with an increase of 12dB in peak levels!
In conventional, VU and average responding meters,
0dB
(or 0 VU)
usually indicates the desired average operating level. On the other hand, the
metering within the Aura8ip follows standard operating practice for digital
signals and provides an accurate indication for when
0dBFS
is reached. If
and when signal peaks reach 0dBFS, there are no more digital bits available
to define the audio signal which results in hard clipping and severe distortion.
The Input meter shown at left is indicating good input levels – peaks are at,
but not above, -12dBFS – good operating practice.
Gain Reduction Meters
Multiband AGC/Compressor and Limiter
– The
AGC/Compressor gain reduction meters display the amount
of processing in each band, and for both the slower AGC,
and faster Compressor.
The gain reduction meters for the multiband limiters
look similar to the meters for the AGC/Compressor, but
have reduced scales more appropriate for limiters.
Metering for each band follows the L, M, H (Low, Me-
dium and High) convention, and the left meter is for AGC
and right for Compressor.
Final Look Ahead Limiter Metering
– The right-most
meter scale within the group of multiband limiter meters
is for the final lookahead limiter. This meter should rarely
show more than 2dB to 3dB of activity.
Normal Gain Reduction
The following is a general guideline for what normal indications might be:
Meter
Minimum Reading
Maximum Reading
Multiband AGC
3dB
24dB
Multiband
Limiter 0dB
6dB
Final
Limiter
0dB
3dB