Dr. Octature

Octal-phase shifted outputs / Low Pass Filter and VCO/LFO

The Intellijel Dr. Octature, another installment in the David G. Dixon 2164 series of modules.

The basis of the module is a 4-pole LPF inspired by the classic “cascaded OTA” design, but realized instead with superior-quality 2164 VCAs.

The “octature” refers to the 8 distinct, phase separated outputs (every 45 degrees, or two sets of four 180-degree shifted outputs). each pair has a different slope: 6db, 12db, 18db and 24dB.

The cascaded-stage design is similar to the filter found in absolute classics such as the Roland Jupiter-6 and SH-101. However, when put into self-oscillation this filter becomes a stable, 1V/Oct tracking LFO/VCO, with each of the 8 outputs giving a sine wave 45 degrees out of phase with the next.

Features
Coarse and fine tuning
Range switch for LFO (0.017Hz to 300Hz) and VCO (17Hz to 22kHz) modes
VC resonance with logarithmic response for smooth control
1V/Oct temperature stable tracking
Mono / quad resonance gain distribution switch for classic or enhanced performance
Unipolar FM1 and bipolar FM2 attenuated CV inputs
Single PCB design (very shallow/skiff friendly)