Module A-101-1 is a special multitype filter based on an idea by Nyle A. Steiner from the year 1974. Injecting an audio signal into different points of a standard lowpass filter circuit leads to the three filter types, low pass (LP), band pass (BP) amd high pass (HP). For each filter type a separate input is available and the sum of the three filtered signals appears at the common output. Even a notch filter can be realized. In contrast to the original circuit so-called vactrols are used instead of diodes as variable resistors for frequency and resonance control. A vactrol is a combination of a light depending resistor (LDR) and a light emitting diode (LED) both put into a small light-proof case. Vactrol based circuits are known for their soft low-distortion sound.
The three filter audio inputs are normalled via switching sockets, i.e. the BP input is connected to the LP jack socket provided that no cable is plugged into the BP socket (same applies for HP/BP inputs). Each audio input is equipped with an attenuator. The audio inputs are very sensitive and enable distorted sounds too. For both frequency and resonance manual control and several control voltage inputs are available.
Two LEDs display the current frequency and resonance settings.
Width:16HP / 80.9 mm
Depth: 50 mm (measured from the rear side of the front panel)
Current: 30 mA
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