Lavry AD122-96 MX Operation Manual

Contents

Lavry AD122-96 MX Operation Manual Manual pdf 12 page image

AD122-96 MX Operations Manual8Bar-Graph & Display ScreenFINE: OFF 20 METER: -00 0PEAK/HOLD OFF DISPLAY:3Bar-Graph settings:FINE: OFF sets the bar graph display (LED's) for normal audio monitoring. Setting to FINE: ON 20activates the reference meter bridge function, for fine-tuning of signal level to -20dB reference point.The reference point can be set to a level between -10dB and -20dB by changing the “20” to the desiredreference level. The incoming signal is displayed in 0.2dB increments around the reference point. Fine-tuning of signal levels may be done via an external volume control or by tuning the GAIN adjustmentpots located on the front panel (the adjustment requires a small screwdriver).The normal setting, “METER:-00” is used for showing peak and peak-hold levels ranging from 0 to -55dB (from full scale). The display may be extended to indicate lower level activity such as noise andDC offset.Meter Setting Display range Read Bar-GraphMETER:-00 0dB to -55dB Read Bar Graph panel indicatorMETER:-30 -30dB to -85dB Add -30dB to panel indicatorMETER:-60 -60dB to -115dB Add -60dB to panel indicatorMETER:-90 -90dB to -145dB Add -90dB to panel indicatorWhile this feature is useful for determining noise floor of the incoming signal, a few comments are inorder:1. The Bar Graph displays a sum of AC signal "riding" on a DC offset. Monitoring low-level signals(such as noise floor) requires prior setting of DC removal at the audio control screen DCREMOVAL ON.2. Viewing the noise floor takes some getting used to. The display shows a true picture of peak andpeak-hold information; the blinking of LED's is due to low level quantizations. Peak readings are atabout 11dB higher than the rms noise for flat noise spectrum.3. Measuring the converter noise floor is best done with specialized equipment (such as LavryEngineering’s Model LE3000S). To verify the proper converter noise floor via extended metering youmust activate the DC removal (DC REMOVAL ON) and connect a low value resistor (0-1k Ohm)between pins 2 and 3 of the analog input XLR connector. Floating high impedance analog inputs aresusceptible to noise pickup.Peak/Hold indication:When set to ON, the peak level is held until a front panel switch is depressed. In addition, the “MAX”LED will turn on and stay on when output data hits the full-scale value. The appropriate 0dB bar-graphlamp (left or right) will start blinking. The “MAX” and corresponding lamps may be reset by pressingany of the front panel switches. When PEAK/HOLD is OFF, the MAX lamp will flicker when a singlefull-scale sample is encountered.Display contrast: The LCD display may be adjusted from 0 to 7.The “0” in the upper right corner of the screen is no longer used for setting a parameter in the MXmodel. It can be changed to a “1,” but it should normally be set to “0” as the default setting.