The AM-3B PHASE MONITOR - the complete tool for all stereo audio applications. Real time visual and audible monitoring of stereo audio phase, program VU levels, Peak threshold levels, including L+R or AUX - all in one complete system.

A quick glance by the operator gives a complete "picture" of the audio signal. Audio level monitoring, the B&B Systems Phase Monitor CRT display, selectable dual input sources, and a speaker/headphone output with level control allow you to easily avoid out-of-phase stereo or peak audio distortion.


  • Dual three-channel inputs, selectable A/B and a separate level control for an isolated power amp/speaker feed.
  • Speaker/headphone output, selectable for Stereo, L+R, or AUX and follows the A/B input selection.
  • CRT X/Y B&B Systems Phase Monitor, with calibrated graticule for phase.
  • Three ANSI calibrated VU meters with Peak overload LED indicators for each channel, selectable between two three-channel input sources. Third meter is selectable between L+R or AUX.
  • Self-contained in only 2 EIA rack units.
  • Magnetic and EMI/RF shielding.


AUDIO: Two sets of three XLR female connectors for left and right audio, and AUX audio. All inputs are balanced and buffered with greater that 50k ohm input impedance. Inputs can be set for resistive termination according to studio operating standards. Each of the two three-channel input groups are selectable via a front panel switch.

SCOPE: Oscilloscope display, bandwidth limited to audio frequencies of 20 Hz to 20k Hz. Display calibration can be adjusted to conform to studio line level. Proper stereo phase relationship of left and right channels is marked diagonally on the graticule.
VU METERS: The VU meters meet all electrical and ballistic specifications established by the Bell Laboratories and ANSI 16.5-1954, as required by broadcasting and sound engineers. Each meter features a LED Peak overload level indicator with internally settable threshold.

SPEAKER LEVEL OUTPUTS: Two output connectors follow a front panel attenuator and bridge the selected input group. A selector allows monitor outputs in either Stereo, L+R, or AUX.

115-120/220-260 VAC, 50/60 Hz, 75 Watts max.

3/12" x 19" Wide x 17" Deep, 2 EIA rack units, 25 Lbs. (11.4 Kilo).

B&B Systems Phase Monitor showing in-phase program material, with good stereo separation.

Monitor showing out-of-phase program material.

Out-of-phase tone - quickly detect phase errors in your system.