3.7 Since the primary use of the PSG is to produce sound for the highly
D/A Converter
imperfect amplitude detection mechanism of the human ear, the D/A
conversion is performed in logarithmic steps with a normalized
Operation
voltage range of from 0 to 1 Volt. The specific amplitude control of
each of the three D/A Converters isaccomplished by the three sets of
4-bit outputs of the Amplitude Control block, while the Mixeroutputs
provide the base signal frequency (Noise and/or Tone).
Fig. 9 illustrates the D/A Converter output which would result if noise
and tones were disabled and an envelope-controlled variable ampli-
tude were selected.
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