Dorrough 280 Technical Instruction Manual
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Dorrough 280 Technical Instruction Manual

Digital loudness meters
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MODEL 280-D
Model 280-D
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MODEL 280-E
Model 280-E
Digital Loudness Meters
Model 280 and 380
U.S.A.
U.S.A.
Technical Instruction Manual
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Summary of Contents for Dorrough 280

  • Page 1 Digital Loudness Meters Model 280 and 380 – 1 – 2 – 3 -39 -38 -37 -36 -35 -34 -33 -32 -31 -30 -29 -28 -27 -26 -25 -24 -23 -22 -21 -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 –...
  • Page 2 Digital Loudness Meters Model 280 and 380 April, 1999 Copyright © 1994 and 1999 by Dorrough Electronics, 20434 Corisco St., Chatsworth California, 91311. PH 818.998.2824, FAX 818.998.1507. Dorrough Electronics reserves the right to make changes and improvements in product specifications without notice.

  • Page 3: Loudness Monitoring

    In 1980, after years of hands-on experience and frustration with both conventional VU and PPM metering, Dorrough research led to the introduction of the Dorrough Model 40 Loudness Meter. By providing an easy to understand display showing the relationship between integration of RMS and peak level display, the model 40 was an overnight success.
  • Page 4 The Dorrough Loudness Meter gives you a much more accurate picture of the actual energy content of audio program material than conventional metering. By simultaneously displaying two ballistics, the Dorrough Loudness Meter shows you the relationship between average and peak.
  • Page 5 Horizontal or Vertical Mounting The model 280 is designed for horizontal mounting while the model 380 is designed for vertical mounting. Both models are offered with two scale ranges, a standard 40 dB range (-D suffix), and an expanded 60 dB range (-E suffix).

  • Page 6: Two Channel Display

    Figure 1-2. Model 380 Front Vie 40 dB or 60 dB Scale Both the model 280 and 380 are available with either 40 dB or 60 dB scale ranges. The “D” suffix (40 dB) uses 40 discrete LED indicators, each representing one dB.

  • Page 7: Overrange Indication

    Peak Hold Functions Both the model 280 and 380 provide three peak hold functions: 3-second peak hold (normal), indefinite peak hold, and no peak hold. These functions are selected through a three-position toggle switch (supplied), or if only a single function is desired, jumper selected on the DLM main circuit board.
  • Page 8 Bezel supplied. Weight Approximately 1 pound. Options – Rack mount adapter for one to three units (model 280 only). – 40 dB or 60 dB scale overlay. Accessories Supplied – 120VAC or 220VAC power adapter – Peak Hold Toggle Switch (3-position) with cable and plug –...

  • Page 9: Installation

    2.3. Mounting The model 280 is designed for horizontal mounting in a console or rack. For console installation, the unit mounts in a standard 1.45” by 5.0” cutout. If you intend to install the unit in a rack, a optional rack adapter are available as shown in Figure 2-1.
  • Page 10 -5 -4 -3 -2 -1 0 U.S .A. Figure 2-1. Model 280 Rack Mount Adapters 2.4. Electrical There are three types of electrical connections to the DLM: digital signal input (and optional output), peak hold function selection, and DC power.
  • Page 11 The DLM provides a buffered digital signal output, which may be used for Note: bridging. This feature is particularly useful when connecting unbalanced consumer equipment with low signal level outputs (< 500 mV) to profes- sional balanced lines. In either case, the buffered digital output signal is approximately 4 volts.

  • Page 12: Power Connections

    Peak Hold Switch Connections Two methods of Peak Hold function control are available. If you wish to have the option of selecting either normal operation (peak hold for 3 seconds), indefinite peak hold, or peak hold disabled, the three position toggle switch supplied (or its electrical equivalence) must be installed.
  • Page 13 When using the AC power adapter supplied, connect the positive lead (the lead with the white tracer strip) to the positive DC terminal on the DLM’s Euroconnector, and the negative lead (solid black) to the negative DC terminal. Refer to Figure 2-4 for connection details. When suppling multiple DLM’s from a common power source, the supply must be capable of furnishing approximately 600 milliamperes per meter.

  • Page 14: Initial Setup

    2.5. Initial Setup Because the signal and monitoring electronics are entirely digital, no calibration or adjustments are necessary. To verify operation, apply a tone (in the AES/EBU digital format) to the DLM’s input. The meter should indicate precisely the level of the signal. If you do not see an indication on the DLM, perform the following: •...

  • Page 15: Operation

    3.3. The Peak Hold Switch Both the model 280 and 380 provide three types of peak hold functions: normal operation (3-second peak hold), indefinite peak hold, and peak hold disabled. These function are selected through a three-position toggle switch (supplied).
  • Page 16 Normal (3-Second Peak Hold) Normal operation (peak hold functions disabled) is provided at the center position of the toggle switch, or through jumpering as described in Section 4 of this book. In this mode, the highest peak is held for a period of three seconds before resetting.

  • Page 17: Maintenance

    Maintenance 4.1. General Because the signal and monitoring electronics are entirely digital, no calibration or adjustments are necessary. Generally, the DLM requires no periodic maintenance other than perhaps wiping any dust accumulation from the scale with a soft damp cloth. 4 miniature incandescent lamps provide scale illumination.

  • Page 18: Jumper Settings

    4.3. Jumper Settings Figure 4-1 illustrates the jumpers on the DLM’s main circuit board, while the following table defines their settings and functions. XFORMER XFORMER Figure 4-2. Jumper Locations Table 4-1. Jumper Functions Across Jumper Center Pin Function and: Overrange indication trigger = 1 count over Overrange indication trigger = 4 counts over (*factory default) Indefinite peak hold...

  • Page 19: Return Procedures

    Be sure to complete and return the Warranty Registration Form to activate the warranty. In the event it is necessary to return your model 280 or 380 to the factory for service, in or out of warranty, you must first obtain a Return Material Au- thorization (RMA) number from Dorrough Electronics at (818) 998-2824 or FAX at (818) 998-1507.
  • Page 20 Maintenance...

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