ADC ADDC1 instruction manual Adjusting Input Gain, First Stage Gain, Second Stage Gain Controls

The red 0 LED indicates that a full-scale digital code has been reached and that digital clipping has occurred. Full-scale events as short as one digital sample, will light the 0 LED. Short single-sample digital clipping events are often audible, and all 0 dBFS events should be avoided.

The ADC1 has a very large dynamic range (especially when operating at 24-bit output word lengths). It is wise to use some of this dynamic range to provide more headroom as insurance against clipping. Leave some extra headroom between your highest anticipated peak and the red 0 dBFS LED.

To select the meter scale and peak hold function

•Set the Meter Switch to “H” (up) to enable the Peak Hold function and set the scale to 1 dB/step.

•Set the Meter Switch to “1” (center) to disable the Peak Hold function and set the scale to 1 dB/step.

•Set the Meter Switch to “6” (down) to disable the Peak Hold function and set the scale to 6 dB/step.

Adjusting Input Gain

Input Gain Stages

First Stage Gain

Each channel on the ADC1 is equipped with a 3-position first-stage gain switch. The first gain stage provides exceptional noise performance at gains of 0 dB, +10 dB, or +20 dB. This stage is followed by a second-stage having a continuously variable gain range of -1.3 dB to +22 dB. This gain structure

ADC1 Instruction Manual

provides ultra-high performance at any gain setting between -1.3 dB and +42 dB. The higher gain settings will allow direct connections from many instrument pickups (no DI box required).

To select the first stage gain

•Set the Gain Switch to “0” (center) to select 0 dB gain (unity gain) for the first- stage.

•Set the Gain Switch to “10” (down) to select 10 dB gain for the first-stage.

•Set the Gain Switch to “20” (up) to select 20 dB gain for the first-stage.

Second Stage Gain Controls

The second gain stage of each channel has a 41-detent Gain Control Knob, and a 10-turn Gain Calibration Trimmer. Each channel also has a 2-position Second-Stage Gain Switch. The switch selects either the Gain Control Knob or the Gain Calibration Trimmer. Both controls have a useable range of approximately -1.3 dB to +22 dB.

To use the Gain Control Knob to adjust second stage gain

Set the Secondary Gain Switch to Variable (up) as shown in the diagram below.

Up Position

To use the Gain Calibration Trimmer to adjust second stage gain

Set the Secondary Gain Switch to Calibrated (down) as shown in the diagram below.

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