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Dorrough 21A Vertical Analog Loudness Meter

Dorrough 21A Vertical Analog Loudness Meter

Dorrough 21A Vertical Analog Loudness Meter

B&H # DO21A MFR # 21-A
Dorrough 21A Vertical Analog Loudness Meter

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Overview
  • 1Description

The Dorrough 21A Vertical Analog Loudness Meter is a straight line version of Dorrough's standard 40A loudness monitor. The 21A requires rack mounting and needs an external power supply. It also comes in a handy vertical orientation.

Like the 40A, the 21A has a scale allowing 14 dB of headroom in 1 dB steps from +14 to -25. Access phase correlation, peak hold, sum/diff, and reference mode allowing 0 reference setting to 0.1 dB accuracy, directly or with the optional remote control.

Actual Energy Display
Dorrough Loudness Meters display actual energy content of the program material, regardless of frequency, while still indicating the peak amplitude of the complex audio signal. This feature allows all program material to be adjusted for equal perceived loudness while protecting the peak of the waveform.
Peak and Average Level Metering
The 21A, like all Dorrough loudness meters, simultaneously displays peak and average. The relative difference, in dB, between these two ballistics is derived from the integration time of the persistence scale.
Right and Left In puts for Stereo Mixing
With one instrument, the operator can easily see the stereo mix and avoid classic in-phase/out-of-phase problems as well as center channel buildup causing a mix to seem louder. This is especially important in preparing stereo program material for broadcast, while still being able to maintain monaural compatibility.
In the Box
Dorrough 21A Vertical Analog Loudness Meter
  • 2-Year Warranty
  • Table of Contents
    • 1Description
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    Specifications
    Input Impedance 20k Ohm balanced, 10k Ohm single-ended, +/- 2%
    Common Mode Rejection Ratio 80 dB at 60 Hz, 60 dB at 20 kHz (balanced mode)
    Input Sensitivity -10 dB for full-scale display
    Maximum Input Level +24 dB before clipping
    Signal Path Bandwidth 10 Hz - 25 kHz, +/- 0.25 dB
    Signal Path Distortion Less than 1% THD at 1 kHz, +24 dB input
    Sum Error Less than 0.1 dB at 1 kHz
    Difference Error Less than 0.1 dB at 1 kHz
    Display Resolution 40 LEDs, 1 dB/LED
    Step Size Error +/- 0.25 dB
    Absolute Error +/- 0.25 dB
    Drift +/- 0.25 dB
    Average Time Constant 600 mS, +/- 6%
    Peak Acquisition Period 10 uS, to full-scale, sine input 25 kHz
    Peak Attack Period Virtually Instantaneous
    Peak Decay Period 180 mS, from full-scale to all LEDs off
    Display Update Rate Approximately 10 mS
    Display Duty Cycle Display Time, AVERAGE, PEAK HOLD - 75% Display Time, PEAK - 100%
    Power Supply Input Range 117/237 VAC RMS, -20% to +10%, 50-60 Hz
    Calibration Controls None Needed
    User Controls Left/Right input sensitivity Option DIP Switch A) Peak Auto [ON] B) Difference Mode [ON/OFF] C) Over Level Alarm [ENABLE] D) Under Level Alarm [ENABLE] E) Auto ARMP
    User Port DB-9 Connector A) Alarm relay closure contacts 1 form C, 1A, 30V AC or DC B) Mode control switch (user supplied) C) PEAK function switch (user supplied)
    Dimensions (WxDxH) 1.75 x 8.5 x 3" (4.45 x 21.59 x 7.62 cm)
    Weight Not Specified by Manufacturer
    Packaging Info
    Package Weight 1.85 lb
    Box Dimensions (LxWxH) 12.2 x 9.4 x 6.6"

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