Operation - Viking PA-250 Product Manual

A. Inputs
In the idle state, the PA-250 allows Background Music to the speakers. When any of the three audio inputs are activated,
background music is muted and the activated input is connected. Each input, except Background Music, has front panel
LEDs that light up showing status of activity and audio level. If multiple inputs are activated, the PA-250 will manage
them however the Input Priority is programmed. Both Loud Ringing and Chime Tones will barge in on top of any active
page. When no inputs are active, the PA-250 will fade back to background music.
B. ALC Adjustment
The front panel ALC (Automatic Level Control), adjustment POT allows up to 6dB of dynamic audio compression. When
used, it increases the level of soft spoken pages, and decreases the level of loud spoken pages. It is useful to help
nominalize the volume of voice paging from both the Microphone and Telecom Page inputs. When dialed back to
minimum, the ALC feature is disabled.
C. Bass and Treble Controls
Front panel BASS and TREBLE controls are provided to adjust the paging tonality. Since lower frequencies require
higher power, turning the bass down can allow increased paging volume levels. Turning up the treble can increase
paging intelligibility.
D. Master Volume Control and Peak Limiter
The front panel MASTER VOLUME control adjusts the volume coming from all inputs.
The PA-250 has an integrated Peak Limiter feature that reduces the audio signal peaks by 4dB. Since audio signals
are highly dynamic in nature, this feature allows the average volume level of pages to be 4dB louder than normal before
clipping distortion occurs. The MASTER VOLUME LED blinks on when peak limiting is engaging. If maximum volume
levels are desired, turn up the MASTER VOLUME control until the MASTER VOLUME LED starts blinking a bit during
pages. Then use the 70V speaker taps to adjust the volume of each paging speaker, keeping in mind to NOT go over
a total of 250 Watt accumulative load.
NOTE: If audio sounds distorted, even when the volume is low enough that the MASTER VOLUME LED is not lighting
up, the input circuitry for that source is probably being overdriven. Turn down the front panel trim pot for that input until
the sound is clear.
E. Power LED
The front panel POWER LED serves two purposes. It will light steady a few seconds after the unit is powered up showing
power is applied. Second, it will momentarily wink off showing when the power amplifier is going into current limiting. If
current limiting is observed, here is a list of suggested actions:
1 Turn down the input level of the specific input that is pushing it into current limiting.
2 Turn down the MASTER VOLUME level.
3 Turn down the BASS level.
4 Reduce the number of speakers connected to the PA-250.
5 Reduce the power tap settings of the connected speakers.

Operation

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