Dorrough 400-A - Jumbo-Sized Horizontal Rackmount Analog Loudness Meter for Theater and Concert Environments

B&H # DO400A MFR # 400-A
Dorrough 400-A -  Jumbo Analog Loudness Meter


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The Dorrough 400-A is a very large professional analog loudness meter, visible from distances of over 50 feet, designed for modern theater and concert audio requirements, and offering simultaneous average and peak program display, with separate ballistics and lightning-fast response. This meter is equipped with a 40-LED bar graph, showing 1dB of resolution per LED, and 14dB of headroom.

Stand-alone, 2' wide Analog Loudness Meter with dual dedicated ballistics for simultaneous peak and average readout for theater and concert audio
Microchip processor with accuracy of oscilloscope, ultra-fast response time of 600ms average, virtually instantaneous peak for seamless continuous display of peak/average relationship
Individual left and right XLR inputs for stereo mixing applications, +4 dB factory-calibrated
Display with 40 LED's providing 1dB resolution per LED
Proprietary "A" scale with 14dB of headroom
XLR, 6 DIP switches for function assignments, mini 8-pin DIN port out for access to alarm relays, meter mode functions, and peak hold modes, standard with unit
Input Impedance 20 kOhm balanced
10 kOhm 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, +/- .25 dB
Signal Path Distortion >1% THD at 1 kHz, +24 dB input
Sum Error >0.1 dB at 1 kHz
Difference Error >0.1 dB at 1 kHz
Display Resolution 40 LEDs, 1 dB/LED
Step Size Error +/- 0.25 dB
Absolute Error +/- 0.25 dB (Full Scale -39 dBu)
Drift +/- 0.25 dB
Average Time Constant 600 mS, +/- 6%
Peak Acquisition Period 10 uS, to full-scale, sine input 25kHz
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) 23 x 8 x 4.25" (584.2 x 203.2 x 107.95mm)
Weight 6.9 lb (3.1 kg)
Dorrough 400-A - Jumbo-Sized Horizontal Rackmount Analog Loudness Meter for Theater and Concert Environments
  • Owner's Manual
  • 1 Year Warranty
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