The 760A Stereo Audio Monitor is a simple yet accurate tool that the audio engineer can use to perform setup, monitoring, measuring, and troubleshooting tasks in the studio. There are two special versions of the 760A Stereo Audio Monitor: the 760D and the 760N. All three operate in exactly the same manner, but are set to use different scales for the Bar Graph displays. The display is set for a “Sound Stage” orientation when the 760A is shipped from the factory. This provides a display where monaural amplitudes are oriented on the vertical axis of the CRT. An alternate XY graticule is shipped as a standard accessory with the 760A. This graticule can be installed if you are familiar with or desire the display orientation provided by an XY monitor. Instructions for installing the XY graticule are found in SECTION 3 INSTALLATION. Automatic or manual gain control is front panel selectable. This feature allows flexible control of the pattern size over a wide range of input signal amplitudes. In the absence of an input signal, Z–Axis dimming prolongs CRT life. Bar Graph Three 100–segment LED bars indicate the levels of the left stereo channel, right stereo channel and a selectable third channel. The third bar can be set to display the levels of (L+R)/2, (LR)/2, or the rear–panel AUXILIARY input. Both (L+R)/2 and (LR)/2 are internally derived, and represent half the sum or difference of the input voltages ([VLVR] / 2). In this way when the left and right channels are balanced the sum will be displayed at that same level, while the difference will be displayed at “0”. The EXPAND SCALE control is a momentary contact front–panel push button, which greatly improves the accuracy of level setups. Pressing this button switches to the blue expanded scale which allows accurate setting of the signal level for alignment, as specified by broadcast authorities. For the 760A the alignment level is 8 dB. This level is labeled “TEST”, and is indicated by the “arrow head” scale marks. For the 760D the alignment level is –9 dB, indicated by the “arrow head” scale marks. The 760N alignment level is marked “TEST”, and is at 0 dB. In all cases, the normal scale lines up with the expanded scale at the alignment level. The PEAK HOLD control is a latching front–panel push button. Indicated peaks are displayed for approximately three seconds when this function is selected. Dynamic response characteristics for peak program meters The 760A, 760D, and 760N conform to the dynamic response characteristics of: 760A: EBU–3205, IEC 268–10, and IEEE Proposed PPM specification. 760D: DIN 45 406 760N: Nordic Technical Recommendation N9. Table 1–1 shows the peak bar indication when an isolated tone burst of a given duration is applied. The response shown is relative to the indication for a continuous tone of the same amplitude. The burst must contain at least 5 cycles, which requires a frequency of at least 10 kHz for the shortest bursts.