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AM-55 / Sep 2015
F R O N T P A N E L
AM-55 Front Panel
Meters
On the front panel of the AM‑55 are eighteen columns of multicolored LEDs
representing the audio input levels, mutliband AGC gain reduction, multiband limiter
gain reduction, and the digital and TX 1 and TX 2 MPX outputs, respectively.
Input Level Meters
The input level meters have a scale showing the uppermost 42dB of the AM‑55’s
internal, 24‑bit, 144dB dynamic range. Levels which fall below the ‑42dB point on
the input meter are also the assigned trip levels for automatic input failsafe when that
feature is enabled (see page 3‑12 for input auto failsafe).
Please take note that the levels shown on the Input/Output meters are calibrated in
dBFS which stands for deciBels Full Scale. “0”dBFS is important because it is where
there are no more digital bits available to define the audio. Audio levels can never exceed
0dBFS and severe clipping distortion will result if the audio attempts to exceed it.
Please also note that the LED indicator for the ‑12dBFS level is yellow in order to
warn the operator that there isn’t much digital headroom left above that level. Therefore,
normal input levels will usually fall between ‑24dBFS and ‑18dBFS with an occasional
peak at ‑12dBFS. The input meters always show the audio input level from the currently
selected input, analog or digital (AES3 or WheatNet‑IP).
AGC Meters
There are six columns for the multiband AGC gain reduction meters. The first column
stands alone and indicates how much gain the iAGC, or Intelligent AGC, is controlling
the multiband AAGC’s behavior. This scale has a 21dB range. See Chapter 3 on the
i
AGC for a deeper explanation of its behavior and tuning.
The next five meter columns show the amount of gain reduction being done in each
of the AGC’s five frequency bands. Normal gain reduction values will run somewhere
around -6 to -15dB. See Chapter 3 on the multiband AGC for a deeper explanation of
its behavior and tuning.
