To begin this circuit, I needed to amplify the signal from the pick-up on the guitar. Thus, I designed a non-inveting op-amp with a gain of 2.
Electric Guitar
Introduction
In this project, I designed a filteration circuit to filter out the sound of one note in a six-string electric guitar. I choose tp filter out C, which corresponds to 81 Hz.
Project
Twin-T schematic, Twin-T schematic with approximate component values, and the corresponding AC-sweep
To filter out one specific note, C in this case, I decided to use a Twin-T notch filter. Using the design equations for a Twin-T bandpass filter and avaliable componets, I computed the necassary component values to filter out a C at 81 Hz. After this, I ran an AC-sweep analysis on LTSpice. After this, I placed the non-inveting amplifier as the input to the Twin-T notch filter.
The current iteration of this circuit had one main issue; the band-stop was too narrow. To fix this, I introduced negative feedback within the Twin-T notch filter using design equations from https://www.electronics-tutorials.ws/filter/band-stop-filter.html. First, I decoupled the out of the Twin-T notch filter by adding a unity gain buffer. Then, using a voltage divider, I decreased the output of the unity gain, which is the same as the output of the Twin-T notch filter. I chose to decrease the voltage by a factor of 2, which has the effect of doubling the bandstop region. At this point, I needed to connect the negative feedback back to the Twin-T notch filter. Again, I used a unity gain buffer to decouple the two parts of the circuit.
Schematic of the circuit with the added modifications, and the output of an AC-sweep for this circuit
Bread-board circuit, and output
I constructed the circuit on a bread board (shown on the right). Then, I introduced a 2 Volt peak-to-peak signal at 81 Hz (output shown to the right). In the output, the input signal is in yellow, and the output signal is in blue. The modified Twin-T notch filter successfully filtered out an 81 Hz signal. Now, it could be used for an electric guitar!
While this project was successful technically, I also gained valuable expierence in circuit design. One area that I learned about was compartmentalization. Breaking up this circuit in compartments (non-inveting op-amp, Twin-T notch filter, unity gain buffer, and voltage divider) to test the functionality of each compartment seperately was effective. This proccess also made combining the compartments together easier because I already new if each part functioned.