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Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation

B&H # DO21B Mfr # 21-B
Usually ships in 7-14 business days

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This is a Special order item. Est. arrival at B&H is 7-14 business days (subject to availability). Your order will be charged at time of shipment. Item is non-cancelable and non-returnable.
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You Pay: $449.95

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.
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) 2.8 x 8.5 x 6.5" (7.11 x 21.59 x 16.51 cm)
Weight Not Specified by Manufacturer
Dorrough 21B Vertical Analog Loudness Meter with Percent Modulation
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