Dorrough 20-A Meter

Years of hands-on experience and frustration with both VU and PPM metering led to the development of the DORROUGH Loudness Monitors. DORROUGH’s research has established the relationship between integration time, RMS metering and the display of peak levels.

The DORROUGH Loudness Monitor displays, in an easy-to-read format, the actual energy content of the program material, regardless of frequency, while still indicating the peak amplitude of the complex audio signal. It allows the operator to ride levels in a manner such that all program material can be adjusted for equal perceived loudness while protecting the peak of the waveform. Now, one meter gives you more complete and more usable information than any combination of peak hold, VU and PPM indicators. The DORROUGH Loudness Monitor integrates on the same scale, two ballistics, showing the relationship between the average and the peak. It simultaneously displays peak and average, and the relative difference, in dB, between these two ballistics is derived from the integration time of the persistence scale.

The operator has only to adjust the level until either the peak or persistence reference is reached. This will result in the maximum level, regardless of program content. Material with or without compression can easily be matched for the same listening level.

Each DORROUGH Loudness Monitor features Right and Left inputs for use in stereo mixing applications. With one instrument, the operator can easily see the stereo mix and avoid the classic in-phase/out-of-phase problem. “Center channel build-up,” the addition of in-phase or monophonic material which causes the mix to be perceived as louder, will appear as a sudden increase in level. This is especially important in preparing stereo program material for broadcast, while still being able to maintain monaural compatibility.

40 Series
The 40-A series Loudness Meters are considered the standard models with built-in power supplies. They are the large ARC-Style, three color LED display single channel meters.

The Remote Control is now available for these units and will access the functions of phase correlation display, peak hold, sum/diff, and activate a reference mode allowing for accurate 0 setting within .1dB. A red LED notification alarm is present on the front of the unit.

40-A
The 40-A has a scale showing 14 dB headroom in 1dB steps from +14 to -25.