Photo Wah Mod for vintage cassette recorder

Light sensors are common in automatic applications like street lights, but here we will be using one to control the volume of a vintage audio device. This mod is a simple sub-circuit that may be used in all sorts of different projects and combinations but first we need to understand these unique electronic parts.

Photoresistors are light sensitive sensors that act like variable resistors. When light on the sensor increases, resistance decreases.

Photoresistor ( aka light sensor, photocell or cds detector )

We will use this same circuit to make a light sensitive wah effect pedal in a future tutorial so try to source a few extra parts!

LED panel mounts are compatible with photoresistors

First locate the potentiometer connected to the volume dial of your battery powered audio device and try to note the way each leg is wired.

Modified volume circuit

We are trying to confirm that the potentiometer is arranged like a voltage divider so that we can insert a photoresistor at the point where the volume dial receives audio from the pcb.

Our goal is to control volume with the wave of our hand, but more specifically we want the volume to increase with light and decrease with darkness. Correct placement of the photoresistor is important to ensure the desired behavior is not inverted. We will also use an SPDT switch to bypass the effect.

Front panel interface for easy access to effect for live expression

Watch the demo below and try this project for yourself! let me know if you have questions in the comments section! Thanks for your support!

Leave a Reply

Your email address will not be published. Required fields are marked *