Dual Waveform Converter / Processor

The AS3397 is a complete system for the generation and processing of audio waveforms in electronic musical instruments. Intended to be driven from digitally generated square or pulse timing signals, the device includes two independent waveform converters, a mixer for voltage controlling the relative balance between the two waveform converter outputs, a dedicated four-pole low—pass voltage controlled filter with voltage controllable resonance, a VCA for allowing one
converter output to frequency modulate the filter, and panoramic output VCAs. All control inputs are high impedance, low bias current inputs which range from 0 to +5V, a feature which eliminates the usual Sample & Hold Buffers in a multiplexed DAC system. Each waveform converter is capable of forming numerous continuously variable waveforms, including sawtooth, triangle, clipped triangle, and variable width pulse, and allowing various combinations of these to be selected. The frequency of these waveforms is equal to the input digital timing signal (typically generated by a programmable divider), allowing precise and stable control of pitch. Additional VCF input gives flexibility in system design. Low noise, low feedthrough filter keeps the peak-to-peak output level constant as the resonance is varied, producing a rich and full resonance sound. Special attention has been paid to the filter to ensure low intermodulation distortion for clean processing of even complex signals.

SOIC-28 package



  • Complete sound synthesis system: two multi-waveform converters, 4-pole VCF, CV mixer, and panoramic VCA
  • 0 to +5V high Z control inputs for direct interface to CMOS multiplexer from system DAC
  • Numerous waveforms and waveform combinations possible for timbral variety
  • Independent and continuously variable waveshape and pulse width for each converter
  • Filter FM
  • Constant output v.s. resonance VCF characteristic
  • Open loop VCF design for rich sound
  • Low noise, low IM distortion VCAs
  • Low VCA feedthrough without trimming