Modded Low-Octave '81 Octavizer PUBLIC

Circuit that generates two lower octaves.

Circuit generates two lower octaves and blends them with the unaltered input signal. Battery operated. Circuit is based on the "Octavizer" in magazine 99 IC Projects, published annually, 1981 edition, p. 93-94. Available online at https://archive.org/details/99ICProjects1981/page/n87/made/up . Controls Include: Direct Send, Input DC Adjust, multivibrator Trigger level, flip-flop Rate, Cancel button, octave Blend, and Output Gain. The circuit is intended for 6-string guitar. Alignment Procedures: With unit OFF, put Cancel button in OFF position and set Input DC Adjust to 0% (ground) but all other controls to 50%. Connect unit output to an amplifier's input set for low volume. Plug the guitar into the unit input and turn the unit ON. While playing a single note, slowly turn Trigger down. Oscillations will occur. Keep turning Trigger down until oscillations stop, then leave the control at that setting. Next, turn Direct Send to 0% but Blend all the way to full 1st Oct. While playing a note, turn Input DC Adjust up until the output octave is close to half the frequency of the input signal (i.e., 1st lower octave), then use Trigger to fine-tune, then set Input DC Adjust for longest sustain. Now play the highest note on the guitar. The output lower octave should also be at half the frequency (i.e., 1st lower octave). If there is static or the lower octave is too low, set the Rate control for best sound. Now, while playing normally (notes and chords), go back-and-forth between Direct Send and Trigger until obtaining maximum sustain but with the least false-triggering (octave too high or too low). You should now be able to use the Blend control to choose between 1st and 2nd lower octaves (or both at 50% setting). Special Settings: For raspy bass sound, set Direct Send very low or 0% but Blend to 1st Oct. For picking-force-sensitive playing, where higher octaves can be triggered by more forceful playing, set Blend to 50% and adjust Direct Send until 1st and 2nd lower octaves are of equal loudness. Use the Cancel button to disable the octaves, though the Direct signal will still be present. And while simulator verified, treat the circuit as experimental. Breadboard test before soldering. And house in a grounded metal enclosure.