Buchla 297 Infinite Phase Shifter

The Model 297 Infinite Phase Shifter displaces the phase of an applied signal by up to 1800 degrees, depending on frequency and number of stages selected. The phase shifted signal may be combined with the original to create a moderately warped comb filter with complimentary outputs. Notch density and depth can be varied through feedback
(resonance) and stage selection. A wide range sweep oscillator enables the familiar cyclical phase shift effect.

All parameters (phase shift, notch depth, sweep rate, sweep depth, resonance) are voltage controlled, with processing control inputs where appropriate. A built-in envelope follower facilitates the creation of amplitude-dependent effects.

The 297 is capable of "barber pole" phasing, with the phase shift (and the consequent filter peaks and notches) continuously moving in one direction. Unique circuitry provides (or consumes) the extra time involved in this process. The rate of change can be varied up to 2.5
octaves per second in either direction and is voltage controllable.

Note that the 297 is not amongst the e series and its settings cannot be internally stored.