Dorrough 40-A Instruction Manual

Digital Loudness MetersModel 280 and 380Technical Instruction Manual0–1–2–3–4–5–6–7–8–9-10-11-12-13-14-15-16-17-18-1920212223242526272829303132333435

8InstallationFigure 2-1. Model 280 Rack Mount Adapters2.4. Electrical There are three types of electrical connections to the DLM: digital signal input

Installation 9Note:The DLM provides a buffered digital signal output, which may be used for bridging. This feature is particularly useful when connect

10 InstallationPeak Hold Switch ConnectionsTwo methods of Peak Hold function control are available. If you wish to have the option of selecting either

Installation 11When using the AC power adapter supplied, connect the positive lead (the lead with the white tracer strip) to the positive DC terminal

12 Installation2.5. Initial SetupBecause the signal and monitoring electronics are entirely digital, no calibration or adjustments are necessary. To v

Operation 13Operation 33.1. GeneralOutside of manually setting the peak hold function desired, operation of the DLM is automatic. Because the AES/EBU

14 OperationNormal (3-Second Peak Hold)Normal operation (peak hold functions disabled) is provided at the center position of the toggle switch, or thr

Maintenanc 15Maintenance 44.1. GeneralBecause the signal and monitoring electronics are entirely digital, no calibration or adjustments are necessary.

16 Maintenance4.3. Jumper SettingsFigure 4-1 illustrates the jumpers on the DLM’s main circuit board, while the following table defines their settings

Maintenanc 174.4. Lamp Replacement ProceduresScale illumination is provided by two miniature incandescent lamps on each side of the scale (four total)

Digital Loudness MetersModel 280 and 380April, 1999Copyright © 1994 and 1999 by Dorrough Electronics, 20434 Corisco St., Chatsworth California, 91311.

18 Maintenance

Introduction 1Introduction 11.1. Loudness MonitoringDouble StandardsFor nearly 60 years the world has used two different standards for audio monitorin

2 IntroductionThe Dorrough Loudness Meter gives you a much more accurate picture of the actual energy content of audio program material than conventio

Introduction 3New ChallengesThe wider dynamic range provided by this standard also poses new challenges in monitoring. The trend to obtain a “hotter”

4 IntroductionTwo Channel DisplayAs defined by the AES/EBU Digital Audio specification, two audio channels (A and B) are encoded into the serial datas

Introduction 5Overrange IndicationOverrange indication occurs when the input signal reaches a point one count over maximum allowed input level. When t

6 IntroductionAccuracy (both scales)Worst case error: +1.4% to -0.8% of full scale. Typical: better than 0.35% of full scale error.Peak Hold Functions

Installation 7Installation 22.1. GeneralInstallation of the DLM is straightforward and easy. When multiple DLMs are installed in a console the use of