DOEPFER / A-101-8 Photo Phasing

Variations

The A-101-8 Photo Phaser is an 8-stage phase shifter using light dependent resistors (LDRs).

This phase shift circuit is a “replica” of the Compact Phasing A manufactured by Schulte in the 70's and is based on the same design, differing only in the lighting control scheme for the LDR, the A-101-8 using LEDs, while the historical masterpiece uses a small incandescent lamp. The A-101-8 uses LEDs, while the historical masterpiece uses a small incandescent lamp. Also, the A-101-8 does not have a built-in LFO, but can be operated from an external control voltage source (LFO, ADSR, random, theremin, ribbon controller, sequencer, MIDI, etc.). Offset (the reference value for phase shift) and modulation depth (the modulation depth of the external CV) can each be adjusted.

Compact Phasing A did not have an offset controller, only a depth control for the internal LFO. The feedback of the output signal and the mixing of the effect are each set with a knob. An attenuator is provided on the audio input. The module provides two audio outputs (as on the historical masterpiece) and a visual indication of the phase shift status.

Controls
Man. : Manual control of the phase shift reference value.
CV: Attenuator for the signal input to the CVin jack.
Feedb. : Feedback or resonance. (Similar effect to the resonance/feedback/emphasis of the filter.)
Mix : Sets the mixing ratio of the original signal and the phase shift signal appearing at Out1.
Turned fully left : Only the “after modulation*” input signal appears at Out1. (*see note below)
Center : Combination of “After modulation*” input signal and phase shift signal is output to Out1.
Turned fully right: Only the phase shift signal is output to Out1. (For vibrato effects, etc.)
Input Level : Attenuator for the signal input to In
Input/Output
In : Audio input
CV : Control voltage input
Out 1 : Audio output 1 (mixed signal)
Out2 : Audio output 2 ("After modulation *" input signal)
LED : Visual indication of phase shift status
This module has the same characteristics as the historical masterpiece.

The input signal is first processed in the pre-stage and output as a “modulated” input signal (*). This signal is output from the Out 2 pin.
Note: This signal is not processed in the phase shift stage, but is affected by the feedback setting. Only when the feedback value is set to 0, this signal is identical to the input signal; otherwise it contains a component of feedback.
Using both outputs Out 1 and Out 2 as stereo channels produces a spatial stereo sound effect.
The same signal as the input signal can also be output when the Mix knob is turned fully left. In that case, the same signal as the input signal appears only if the Feedback knob is set to 0. If it is not 0, it contains a feedback component.
Historically, the A-101-8 had two types of audio inputs: a 5-pin DIN input and a phone jack input; the DIN socket was for line signals, but the phone jack input amplified the effects pre stage by about 100 times. The A-101-8 replicates this design by incorporating a jumper to change the amplification factor. As long as this module is used in an A-100 system, a lower amplification factor is usually used to avoid distortion.
The eight photoresistors and LEDs are assembled in a small box. The board is made of light-shielding black material to avoid light interference from other modules and bus boards.
The following document shows the location and function of the module jumpers and trimming potentiometers: A101_8_trimming_potentiometers_and_jumpers.pdf

Please note that failure of adjustment by the customer or malfunction due to this will not be covered by the warranty.

Width 4HP
Depth 45mm
Current consumption
+12V : 30mA
-12V : 30mA