Audio Graphic Equalizer Circuit

This is a project circuit for audio equalizer. This circuit is control by single chip op amps. This is the figure of the circuit;


A gyrator is a circuit using active devices and transistors to simulate an inductor. In this case the gyrator is the transistor acting with R1, R3 and C2. It could just as easily be a unity gain op-amp (which gives superior performance). The circuit includes three formulae: one which gives f, the centre frequency of the band. The second shows how the Q is related to the capacitor ratio. The third shows the impedance presented by the circuit. Note that this includes 3 terms, the first purely resistive, the second is the capacitive contribution from C1 and the third is an inductive term from the gyrator.

3 Band Equalizer Circuit

This is a circuit for a tone control using 3 band equalizers. This circuit is based on single chip op amps LF351. This circuit having three ranges, bass, middle and treble controls. This is the figure of the circuit;


With a single chip op amps LF351, it is easy to make equalizer offers three ranges, low frequency, mid frequency, and high. With component values shown there is approximately +/-20dB of boost or cut at frequencies of 50Hz, 1kHz and 10kHz. Supply voltage may be anything from 6 to 30 Volts. Maximum boost 20dB is only realized with maximum supply voltage of 18 Volt.

Low Impedance Loads Using LT1210 IC

This is a circuit for impedance load of voltage. This circuit is work using transformer coupling that is frequently used to step up transmission line signals. This circuit is based on LT1210 IC. This IC is fast and capable of delivering high levels of current. They can be readily compensated for reactive loads and are fully protected against thermal and short-circuit faults. This circuit is simple design. This is the figure of the circuit.


The operation of this circuit is begun from a transformer-coupled application for ADSL in which an LT1210 drives a 100W twisted pair. The 1:3 transformer turns ratio allows just over 1W to reach the load at full output. Resistor RT acts as a primary side back termination and also prevents large DC currents from flowing in the coil. The overall frequency response is flat to within 1dB from 500Hz to 2MHz. Distortion products at 1MHz are below – 70dBc at a total output power of 0.56W (load plus termination), rising to –56dBc at 2.25W. If RT is removed, the amplifier will see a load of about 11W and the maximum output power will increase to 5W. A DC blocking capacitor should be used in this case. [Schematic source: Linear Technology Corporation, Inc].