Analog Monitor FAQs

Q : How are the various models of Dorrough Audio Meters different?
A: All Dorrough Loudness Meters feature the same Dorrough Practical Standard (DPS) ballistics. The units are available in different sizes for stand-alone, rack-mount, and console-mount applications. There are also a variety of scale options. All meters feature high-resolution 40 LED displays.

Q: What are the different scale options?
A: Standard scale options include:
"A" Scale (14dB of headroom)
"B" Scale (Primary scale expressed in percent of modulation -- "0" referenced to 100, with a secondary "A" scale)
"C" Scale (20dB of headroom)

Q : What is the input impedance of your analog meters?
A: All Dorrough Loudness Meters have an input impedance of 20k-ohms balanced, and 10k-ohms single-ended.

Q : What are the display time-constants used in your meters?
A: The average signal level display uses a time constant of 600 mS, while the peak display is virtually instantaneous. For background information on these ballistic characteristics, refer to the Audio Engineering Society's published Preprint 2567 (B-1).

Q : What is the display resolution of your meters?
A: The standard analog 40 dB scale provides a resolution of 1 dB per LED. The optional 60 dB scale also provides a resolution of 1 DB per LED, except for the rightmost 10 LEDs, which are 3 dB per LED. The digital meter with the 60 dB scale option is identical.

Q : To what reference level are your analog meters calibrated?
A: All Dorrough analog Loudness Meters are calibrated to a reference level of +4 dB at the factory. This is adjustable to any reference level.

Q : What are the mounting options on the 40-A2 meter?
A: The Model 40-A2 can be used either stand-alone, rack mounted (using our optional one or two-meter rack adapters), or console mounted.

Digital Monitor FAQs

Q : To what reference level are your digital meters calibrated?
A: All Dorrough digital Loudness Meters are calibrated to a reference level of -20 dB. Other levels, such as -14 or -18, can be specified at the time of ordering.

Q : What is the Over Indication level on your digital meters?
A: 1 count over is the factory default setting. The digital meters conform to all formats defined in the AES/EBU Audio Specifications. Included are 24-bit and 16-bit formats. Sampling frequencies are 32 kHz, 44.1 kHz, 48 kHz, and 96 kHz.

Q : How are the input connections made to the digital meters?
A: Electrical connections to the digital meters are made through a standard BNC or XLR connector.


Dorrough produces a variety of digital audio meters, video meters, surround sound meters, and audio and video test products.
One year warranty is standard on all Dorrough products.
The company is located at 5221 Collier Place, Woodland Hills, California 91364 • Telephone (818) 998-2824. Fax: (818) 998-1507. Email: