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Dorrough 21C Vertical Analog Loudness Meter +20 dB

BH #DO21C • MFR #21-C
Dorrough 21C Vertical Analog Loudness Meter +20 dB
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Dorrough 21-C Overview

The Dorrough 21C Vertical Analog Loudness Meter +20 dB is a single-channel version of Dorrough's standard 40 series loudness meter with a straight-line scale display scale allowing 20 dB of headroom in 1 dB steps. The headroom scale is identical to the AES/EBU Digital Standard.

This meter provides 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. It has Phoenix (euroblock) connectors. Rack mounting is required.

Peak and Average Level Metering
The 21C, like all Dorrough loudness meters, simultaneously displays peak and average, in this model down to +20 dB. The relative difference, in dB, between Peak and Average 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 that can cause 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-C Specs

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 except model 60D, +/- 0.25 dB
Step Size Error
+/- 0.25 dB
Absolute Error
Full Scale -39 dBu: +/- 0.25 dB model
+/- 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)
2.8 x 8.5 x 6.5" (7.11 x 21.59 x 16.51 cm)
Not Specified by Manufacturer

Dorrough 21-C Reviews

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