‘Audio tone circuits serve two primary purposes. The first is to manage the signal’s bandwidth as it enters the audio power amplifier. Without constraining the bandwidth, it might be challenging to faithfully reproduce the original signal through the speaker. The second reason is for the sheer pleasure of enjoying music. The process of adjusting the frequency of the signal to be amplified by the audio power amplifier is known as audio tone control. Audio signals are often a mixture of various frequencies, with “BASS” referring to lower frequencies and “TREBLE” to higher frequencies. Audio tone circuits play a crucial role in separating and controlling these frequencies.
It fall into two main categories: active tone control circuits and passive tone control circuits. An audio tone circuit is considered active when it includes an amplifier in the circuit. Conversely, if there is no amplifier present, the circuit is referred to as a passive tone control circuit.
This article will guide you through the process of designing an audio tone circuit with a gain of approximately 25. This design is cost-effective and requires a minimal number of components.
Outline
- Audio Tone Control Circuit Diagram:
- Audio Tone Circuit Design:
- Amplifier Stage:
- Tone Control Circuit:
- Dual Power Supply Circuit Design:
- How to Operate Audio Tone Circuit:
- Audio Tone Circuit Advantages:
- Audio Tone Circuit Applications:
- Audio Tone Circuit Limitations:
- Audio Tone Circuit Design:
Audio Tone Control Circuit Diagram:
Circuit Components:
- TL072 Operational amplifier
- 100k Pot – 3
- Audio jack
- Resistors – 2.2M, 100k(2), 10k(2), 1k(2),
- Capacitors – 100pF, 1uF, 2.2uF, 22nF(2), 220nF, 2.2nF
Audio Tone Control Circuit Design:
The audio tone circuit mainly consists of two sections – one is amplifier and other is passive tone control circuit.
Amplifier Stage:
The amplifier stage in this circuit employs a TL072 non-inverting amplifier configuration. To establish feedback for the operational amplifier, resistor R3 is connected between pins 1 and 2. Pin 2 of the op-amp is grounded through resistor R4. The gain of the operational amplifier is determined by the values of resistors R3 and R4. In the non-inverting mode, the operational amplifier’s gain (Av) is calculated as follows:
Av = 1+ (R3/R4) (R3/R4) (R3/R4) (R3/R4) (R3/R
The input impedance of the first stage is approximately equal to the resistance of R3. Capacitor C2 serves a dual purpose as a decoupling capacitor and a low-frequency cutoff capacitor. Resistor R2 is included to minimize offset effects on the operational amplifier’s output. Ideally, the value of resistor R2 should be roughly equivalent to the parallel combination of R3 and R2.
Tone Control Circuit:
In the tone control section, there’s a 20dB boost capability. Potentiometer RV1 is responsible for adjusting the BASS, whereas the other potentiometer manages the TREBLE. Volume control is achieved through Pot RV2, while Pot RV3 is used to balance the audio. Resistor R7 contributes to the separation between the BASS and TREBLE.
Dual Power Supply Circuit Design:
Circuit Components:
- 12-0-12V, 500mA center tapped transformer
- Diode bridge – 1A
- 680uF Electrolytic capacitors – 2
- 0.01uF capacitors – 2
The audio tone circuit receives electricity from this circuit at +15V and -15V. The voltage is stepped down using a centre tapped transformer. Four 1n4007 diodes make up Diode Bridge D1. This diode bridge is used to convert AC electricity into pulsing DC. The AC ripples are filtered using capacitors.
How to Operate Audio Tone Control Circuit:
- Connect the wires according to the circuit schematic.
- Make sure there is a common connection between the AC and DC while making the connections.
- From the Dual power supply circuit, supply +15V and -15V to the audio tone circuit.
- With the help of the audio jack, connect the audio input to the circuit.
- By adjusting the BASS or TREBLE, you can change the audio tone.
- You can alter the loudness by using the RV2 pot.
Audio Tone Control Circuit Advantages:
- The circuit uses less components and it is cost effective.
- The circuit is portable.
It’s Applications:
- This audio tone control circuit is used in Audio systems to control the audio tone.
- Used in music players to control the bandwidth.
Audio Tone Control Circuit Limitations:
- This circuit is simulated in software and may require some changes in practical.
