AM-4
4 channel
Analog, AES3 Digital, SDI Embedded Digital
Audio Monitor
User Manual
Introduction
The AM-4 is a DSP based digital audio signal monitoring unit, with facilities for monitoring two
Stereo Analog, two AES3 Stereo Digital, and two SDI Embedded stereo signal sources.
The four (two stereo channel) audio level meters display VU and PPM values simultaneously, with
dBu and dBFS scales.
Two stereo audio signals (Analog, AES3 digital, SDI embedded digital) may be monitored at a
time using the level meters. Only one of the two selected stereo sources can be monitored via the
built-in speakers, or with headphones.
The AM-4 supports four monitoring modes: Stereo, Left channel only, Right channel only, and Left
and Right summed mono.
A front panel volume control is provided, for use with speaker and headphone monitoring only.
The VU/PPM meters and Line output levels are not affected by the volume control.
The Analog inputs support either XLR or 1/4“ TRS connections. Analog input sensitivity is
adjustable for each individual input to 4 dBm or –10 dBV nominal levels, by using the
internal jumpers provided on each analog input. AES3 Digital inputs are XLR-3F balanced, and the
SDI input is a BNC connection.
Two Analog outputs, two digital stereo line outputs, and a parallel GPI remote connection are
provided for convenience.
The Out-of-Phase LED will illuminate when phase reversal occurs on one of the stereo channels.
Note that this condition can occur not only for actual accidental phase errors, but may also appear
during segments where signal processing has been applied for sound imaging purposes.
A feature to test for an out-of-phase condition is provided. Pressing and holding down either A or B
pushbutton will reverse the phase of the right channel of the signal while it is being listened to.
This function is very useful to determine whether a stereo signal source is out-of-phase or not.
The Silence LED will illuminate when the signal level falls below the set threshold level, and stays
below the threshold for more than either 5 or 10 seconds in any one of the four channels currently
being monitored. The duration of silence and threshold level to activate this warning is determined
by the user-preset DIP switches.
In the SDI embedded digital audio signal, the carrier is divided into four groups, and each group
can contain up to two stereo digital audio signals. The AM-4 allows selection of one specific audio
group, and retrieval of one or both of the embedded stereo digital audio signals in that group.
Note: The AES3 digital and SDI Embedded digital audio interfaces are optional plug-in boards.