Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation

BH #DO21B • MFR #21-B
Dorrough
Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation
Special Order
Expected availability: 7-14 business days
$449.95

Important Notice

  • This item is noncancelable and nonreturnable.

Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation

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Dorrough 21-B Overview

  • 1Description
  • 2Actual Energy Display
  • 3Peak and Average Level Metering
  • 4Right and Left Inputs for Stereo Mixing

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

Like the 40B, the 21B measures Relative Loudness to Peak Modulation. The meters are calibrated in percent modulation, referenced at 100%. 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 21B, like all Dorrough loudness meters, simultaneously displays peak and average, in this model in a straight-line scale display calibrated in percent modulation, referenced at 100%. The relative difference, in dB, between these two ballistics is derived from the integration time of the persistence scale.

Right and Left Inputs 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.

Dorrough 21-B Specs

Input Impedance20k Ohm balanced, 10k Ohm single-ended, +/- 2%
Common Mode Rejection Ratio80 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 Bandwidth10 Hz - 25 kHz, +/- 0.25 dB
Signal Path DistortionLess than 1% THD at 1 kHz, +24 dB input
Sum ErrorLess than 0.1 dB at 1 kHz
Difference ErrorLess than 0.1 dB at 1 kHz
Display Resolution40 LEDs, 1 dB/LED
Step Size Error+/- 0.25 dB
Absolute Error+/- 0.25 dB
Drift+/- 0.25 dB
Average Time Constant600 mS, +/- 6%
Peak Acquisition Period10 uS, to full-scale, sine input 25 kHz
Peak Attack PeriodVirtually Instantaneous
Peak Decay Period180 mS, from full-scale to all LEDs off
Display Update RateApproximately 10 mS
Display Duty CycleDisplay Time, AVERAGE, PEAK HOLD - 75% Display Time, PEAK - 100%
Power Supply Input Range117/237 VAC RMS, -20% to +10%, 50-60 Hz
Calibration ControlsNone Needed
User ControlsLeft/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 PortDB-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)2.8 x 8.5 x 6.5" (7.11 x 21.59 x 16.51 cm)
WeightNot Specified by Manufacturer
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