Lightspeed Passive Attenuator DIY Project

The circuit was designed to create a volume control with the use of optocouplers to produce a lightspeed passive attenuator.

An optocoupler is a sealed device unit which has high performance LED that illuminates on a light dependent resistor (LDR) where the intensity of the LED determines the volume. It is the main component of this passive attenuator, making the circuit more interesting by eliminates the use of scratchy potentiometer that has contact points in the form of a wiper and the use of switches like the discrete stepped attenuator. The operation of the passive attenuator results to widened soundstage, perfect clarity, separation of instruments, and seemingly infinite detail.

During the process, the internal resistance of the LDR changes with the intensity of the LED. A constant input/output impedance can be generated using a shunt and series combination of optocouplers for the attenuator. This has nothing to do with the setting of the voltage control.

The circuit is not applicable to every audio system because there is no gain since it is a passive type. It is appropriate for use with several sources when the source output impedance is about 100 Ohms.

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