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  • Gain Change

    Gain Change

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    DCArt10/DC Forensics10 provides a Gain Change feature that is useful for correcting loudness deficiencies on recordings, or to provide the additional headroom required before running the graphic equalizer filter (or any other filter or effect that increases signal loudness). Gain Change can be very creatively applied using the contour graphical interface (gain in dB vs. time in percentage of the file length). It can also be utilized globally on a file to amplify or attenuate a signal, or selectively to bring out a weak vocal, etc.

    The following is a summary of the control parameters and the range of adjustment provided for the Gain Change algorithm:
    1. Type (Fade In / Fade Out / Gain Change)
    2. Slope (Linear / Logarithmic / Curve)
    3. Gain Ranges:
      1. +20/-100 dB
      2. +/-20 dB
      3. +/-10 dB
      4. +/-3 dB
    4. Start Level (dB)
    5. End Level (dB)
    6. Shape (Gain vs. Time):
      1. Straight Line: (2 Green Cursors) (start and end gain values)
      2. Curved Line: (4 Green Cursors) (curvilinear inflection point controls)

    The Gain Change graph shows you how you have programmed the gain to change as a function of the selected .wav file time axis. You can use the mouse to drag the two (or four) green control points to establish the time relationship that you desire. Often, a flat line is appropriate; however, sometimes the loudness of old 78s decreased toward the end of the recording by a few dB. This can be corrected by a gain correction starting at 0 dB and ending with perhaps 3 dB (depending on the severity of the problem). The reason this occurred is that the early cutting lathes did not provide automatic gain (or frequency response) compensation controls. When the curve shape is selected, two additional green cursors appear. The two additional green cursors can be moved both vertically and horizontally allowing you to create numerous curvilinear gain vs. time relationships.

    Important Warning:
    Digital systems, like analog systems, can be overdriven to the point of "clipping" the signal. This will produce non-desirous distortion (except on rock n' roll). Before applying a gain increase to a .wav file, study the amplitude of the signal and be sure that you are not adding so much gain as to exceed the dynamic range of the system which is most often set to 2^16 LSB's (or whatever the resolution of the recording that you have digitized). If you do, signals will appear to flatten out horizontally at their peaks on the Source or Destination Workplace displays. If you do indeed notice clipping after a gain change, you can “Undo” this function.
    "Who put orange juice in my orange juice?" - - - William Claude Dukenfield
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