Saturday, May 30, 2015

Stereo Bass Booster Circuit with Simple Mixer


Bass Booster
Bass Booster

A Bass Booster is an audio device, which amplifies the low frequencies (bass) within the audio spectrum. This operates in a similar manner to an audio equalizer. General-purpose equalizers are often not effective at boosting very low frequencies, and therefore many electronics enthusiasts make their own circuit to achieve this purpose. Using following circuit you can boost frequencies below 60Hz.

Stereo Bass Booster circuit

This circuit is an active circuit and used TL074, which include separate four op-amps. Alternatively, you can use any general-purpose op amp such as LM324, TL084, etc. This circuit is not only a bass booster it also include a simple mixer circuit. U1A and U1D are act as mixer, U1B and U1C for the base boosting. I design this circuit for electronic switching. Therefor I used two transistors for it. To enable bass boost connect ‘ubb’ to positive supply. You can use normal switch for it. In addition, it is possible to enable bass boost by applying voltage signal to ‘ubb’, which come from a micro-controller or any other source. This circuit can operate in either single supply or dual power supply.

For single power supply
  • Omit C20 and C21.
  • Connect positive supply to VDD and Ground (0v) to GND or VAA.
  • Max Supply voltage is 12v.

For dual power supply
  • Remove J3 (jumper), C15, R19 and R20.
  • Add jumper (0 Ohms) for R20 it.
  • Connect positive supply to VDD, negative for VAA and Ground (0v) to GND.
  • Max Supply voltage is +/-12v.

Please ignore the U2, R21, C16, C18 and P1. Those are not necessary for the operation of this circuit. These parts are optional because that this circuit and PCB were designed for my personal project.

Now connect output of this circuit with amplifier input and give your input to the mixer side. This circuit is ideal for high quality sound. If you want that unique clean high-bass sound then this circuit can provide it.

Schematic and PCB files were added to the download and you can download from it below.

Thursday, May 28, 2015

10 Band I2C Graphic Equalizer Circuit - 16F628 TEA6360


  • 2016-08-17 - Added small application for calculate frequencies and parts.

10 Band Equalizer
10 Band Equalizer

A graphic equalizer is a high-fidelity audio control that allows the user to see graphically and control individually a number of different frequency bands in a stereophonic system. A typical graphic equalizer consists of several audio filter/amplifiers, each centered at a specific frequency in the audio range. Most graphic equalizers have two identical sets of filter/amplifiers, one for each channel in a stereophonic system.

The gain controls in most graphic equalizers are slide potentiometers that are adjusted by moving a controller up or down. Gain is increased by sliding the upwards. The slide potentiometers for each channel are placed side-by-side, with the lowest-frequency unit at the left and the highest-frequency unit at the right. In this way, the positions of the buttons appear to follow a graphical curve that represents the gain as a function of frequency for each channel.

By using following circuit you can build a 10 band stereo graphic equalizer that can be controlled via I2C system. For this circuit I used two of TEA6360 ICs. Each IC contains two serial five bands equalizer blocks. Therefore, we need two ICs for 10 bands. We can reduce the size of circuit because all the function can be drive via i2C. So that, we do not need connect potentiometers to control the gain of frequency bands like an ordinary equalizer. In addition, we can reduce cost and complexity of circuit using this IC.

10 Band Equalizer circuit

10 Band Equalizer pcb
Circuit on PCB

In my demo code, I used 16F628A micro-controller and single button to set equalizer modes. The modes are ‘Flat’, ’Rock‘, ’Pop‘, ’Jazz‘ and ’Party’. The status will indicate by five LEDs those connected to PORTA. In addition, selected mode saved to device Eeprom and load to ICs when start up. However, according to your choice you can able to change the code.

For example if you need to set gain for each frequency manually, then you can add 1 button to each channel and total 10 buttons. For another example, you can add 3 buttons. One button to raise the gain and other to lower and 3rd one for select desired frequency.

The center frequency of each bands are 31Hz, 62Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz and 16KHz. the Q (quality) factor is 1 to 1.2 and PCB, full schematic and sample code can be downloading in below.

Part List

  • C04, 07, 08, 09 = 0.37uF
  • C10, 11, 12, 13 = 0.18uF
  • C14, 15, 16, 17 = 0.01uF
  • C18, 19, 20, 21 = 0.047uF
  • C22, 23, 24, 25 = 0.022uF
  • C27, 28, 30, 31 = 0.01uF
  • C32, 33, 34, 35 = 0.0052uF
  • C36, 37, 38, 39 = 0.0027uF
  • C40, 41, 42, 43 = 0.0015uF
  • C44, 45, 46, 47 = 720pF


The 5-band stereo equalizer is a 12C-bus controlled tone processor for application in car radio sets, TV sets and music centers. It offers the possibility of sound control as well as equalization of sound pressure behavior of different rooms or loudspeakers, especially in cars.

  • Monolithic integrated 5-band stereo equalizer circuit
  • Five filters for each channel
  • Center frequency, bandwidth and maximum boost/cut defined by external components
  • Choice for variable or constant Q-factor via I2C software
  • Defeat mode
  • All stages are DC-coupled
  • I2C-bus control for all functions
  • Two different module addresses programmable.

Calculator App


on line


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