The Dorrough 21A Vertical Analog Loudness Meter is a straight line version of Dorrough's standard 40A loudness monitor. The 21A requires rack mounting and needs an external power supply. It also comes in a handy vertical orientation.
Like the 40A, the 21A has a scale allowing 14 dB of headroom in 1 dB steps from +14 to -25. 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.
- Actual Energy Display
- Dorrough Loudness Meters display actual energy content of the program material, regardless of frequency, while still indicating the peak amplitude of the complex audio signal. This feature allows all program material to be adjusted for equal perceived loudness while protecting the peak of the waveform.
- Peak and Average Level Metering
- The 21A, like all Dorrough loudness meters, simultaneously displays peak and average. The relative difference, in dB, between these two ballistics is derived from the integration time of the persistence scale.
- Right and Left In puts 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 causing a mix to seem louder. This is especially important in preparing stereo program material for broadcast, while still being able to maintain monaural compatibility.