Recycled Inductance Filter

This article is about an audio filter

made from recycled components

Figure 1: Audio Filter.

Watch this video to see how the circuit works:

Similar Circuits

A similar circuit was published in this article:

https://instructables.com/Recycled-Audio-Transformer-System

The main difference is that this circuit does not provide grounding isolation because we used a coil for the first channel, thus creating a need for common ground for both input and output for that channel.

Step 1: Design the Circuit

I drawn the circuit via https://easyeda.com software.

Figure 2: Circuit Design.

This circuit will not only influence the magnitude of each audio frequency but will also influence the time delay.

The voltage across the speaker will equal to:

Vspeaker = Vin * Zspeaker / (Zinductor + Zspeaker)

In electronic engineering complex number "i" is represented with "j".

Vspeaker = Vin * (Rspeaker + j * Xspeaker) / (j*2*pi*f*L1 + Rspeaker + j*Xspeaker)

(where: Xspeaker = 2*pi*f*Lspeaker, f = frequency (Hz))

Vspeaker = Vin * (Rspeaker + j * 2 * pi * f * Lspeaker) / (Rspeaker + j*2*pi*f*(L1 + Lspeaker))

Inductances in parallel: https://en.wikipedia.org/wiki/Inductor

Vspeaker Magnitude = sqrt(Vin^2) * sqrt((Rspeaker^2) + ((2 * pi * f * Lspeaker)^2)) / sqrt((Rspeaker^2) + ((2 * pi * f * (L1 + Lspeaker))^2))

Step 2: Build the Circuit

The construction of the circuit is very simple:

Figure 3: Place components inside the box.

After you finish soldering the circuit, make sure that you insulate all wires with electrical tape and secure all loose components to prevent short circuits.

Figure 4: Attach components with blue tack.