WBS M405D Rack Mount Extended Range VU/PPM Meter

The M405D has been designed to measure average and peak program levels of audio signals. This instrument is self-contained and mounts in a standard 19" equipment rack. It is powered from a 115 volts, 50/60 Hz power source. A "Range" attenuator, providing 48 steps of 2 dB each, accommodates audio input levels from -50 dBm to +30 dBm for a 0 meter reading. The M405D accepts two inputs (A or B) at the rear of the instrument. Selection between the A or B inputs may be made by a pushbutton selector on the front of the unit. A PJ339A type jack receptacle on the front panel provides a direct input to the instrument. Pushbuttons on the front panel allow the select i on between 600 or 150 ohm source impedances, as well as presenting a matching or a bridging load to the source. An act i ve high pass fi Iter in the M405D provides a 24 dB per octave roll-off with its -3 dB point set to 250 Hz. When this filter is inserted, it provides a 60 Hz hum rejection in excess of 40 dB. A headset jack receptacle on the front panel permits the user to listen to the signal being metered. This headset output is also extended to the rear terminal strip and may be utilized as a line feed for miscellaneous monitoring equipment. An unbalanced 8 ohm speaker output allows a small monitor speaker to be driven directly from the M405D (the maximum output is 3 watts). 

• Range: -50 dBm to +30 dBm in 2 dB steps for 0 VU or 0 PPM readings. 
• Input Selection: Pushbutton selects between two sources. ADC PJ339A type jack on front panel provides direct input. 
• Source Impedance: 600 ohms or 150 ohms. 
• Input Impedance: 600 ohms, 150 ohms or 20k ohms.
• Attenuator Tracking: +/- 0.25 dB per step (non accumulative).
• Meter Ballistics: VU: Complies with ANSI C16.5 PPM: Comp lies with BSI BS4297. 
• High Pass Filter: -3 dB at 250 Hz. -24 dB at 120 Hz. 
• Frequency Response: Metering: +/- 0.25 dB from 30 Hz to 15 kHz. 
• Monitoring Outputs: +/- 0.5 dB from 50 Hz to 10 kHz. 
• Total Harmonic Distortion:  Headset Output - Less than 1%, 50 Hz to 10k Hz (measured at any input level and at +24 dBm output level). Speaker Output - Less than 1%, 50 Hz to 10 kHz (measured at any input level and at 3 watts, 8 ohms output level). 
• Noise: 40 dB below 0 VU or 0 PPM reference. 
• Output Impedance: Headset Output: 150 ohms. Speaker Output: 2 ohms.