User manual

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AMP1-DA User Manual P/N 821530 Rev-C

Section 3: Technical Information

Series II Level Meter Rear Panel DIP Settings

Line Level (Auto) Calibration, Reference Level, and Display Mode

This 6-section DIP switch sets the Line Level Calibration, Reference Level, and PPM/VU Display Mode. See below.

Line Level (Auto) Calibration:

The unit is calibrated at the factory. To recalibrate:

1) Turn on the power.

2) Apply the desired reference level (nominal 0) signal to all channels.

3) Make sure the Reference Level DIP sections (2 and 3) are set to the nearest level of the input signal being applied for calibration

(i.e., 0, +4, +6 or +8). The user should make sure that the signal applied to all four channels is within +/- 4 dB of the reference

level selected by DIP switch sections 2 and 3.

4) Place DIP section 1 in the DOWN position.

5) Wait 10 seconds. The unit will remove the previous calibration and the new calibration will be applied.

6) Place DIP section 1 in the UP position and return unit to service.

7) Only ONE auto-calibration attempt may be made for each cycling of AC power to the unit. Once the Line Level Calibration

DIP switch has been placed in the CAL position, it is necessary to cycle the power before that DIP switch will be functional again,

EVEN if a calibration attempt was unsuccessful.

If one wishes to calibrate again, turn off the power to the unit and repeat steps 1 through 6.

Reference Level:

DIP switch sections 2 and 3 determine the Reference Level, which adjusts the level of the input signal and the resultant level

displayed on the LED bargraphs. Factory setting is +4 dB. See DIP switch diagram below for settings.

Bargraph Display Mode:

DIP switch sections 4 and 5 determine how peak levels are displayed for the associated meters on the front panel. There are four

possible settings; VU Only, VU-PPM Floating Segment, PPM Only, and PPM-PPM Floating Segment. The VU Only

selection has a VU floating segment when a Peak Hold value is selected using the Internal 10-Position DIP Switch Module (see

page 19). The factory default setting is VU-PPM Floating Segment. See diagram below for DIP settings.

Meter Calibration NOTE:

For more accurate indication of signal levels, meters are tuned to effect a “rounding” function, which occurs BETWEEN the

thresholds of any two bargraph segments. This means the level meter zero LED segment will turn on at one-half the smallest

spacing between LED segments (mid-scale resolution) before that segment's scale indication. Below are the offset amounts for

each of the two types of meter.

26-Segment Meters: The "rounding offset" is 0.5 dB for the Analog (extended VU), Digital, Nordic, BBC, and

DIN scales. It is 0.25 dB for the VU scale.

Example: Using the Analog (extended VU) scale, a meter calibrated for a +4 dBu nominal level will actually turn the zero

LED segment of the level meter on at +3.5 dBu (and so all segments will turn on at 0.5 dBu before that segment’s silk-

screened scale indication).

Calibrate

Operate

+6 dB

+8 dB

123456

Meter Calibration Reference Level

Display Mode

Note: Position-6 of DIP switch is NOT used.

AMP Series Level Meter Rear Panel DIP Switch Settings

312 654

+4 dB

0 dB

VU-PPM

Floating Segment

PPM-PPM

Floating Segment

534 6

VU Only

PPM Only

See the "AMP Series Level Meter Internal 10-Position DIP Switch Settings" diagram on page 19 for separately setting the

Peak Hold and PPM Ballistics characteristics.