Pocket headphone amplifier

john April 7, 2010 19 Comments

Description.
Here I present a very simple and powerful headphone amplifier using OPA134. In addition to the IC OPA134, the circuit uses only few passive components and can easily generate a lot of sound from even the most inefficient headphones and there will be no compromise for the quality.
OPA134 is low noise, low distortion operational amplifier from BURR-BROWN semiconductors and it is exclusively meant for audio applications. The FET based input stage provides the IC with high input impedance and it makes the circuit very flexible in terms of the audio source. You can plug almost all types of sound sources like, mp3 players, iPods, mobile phones etc to the circuit.
In the circuit IC OPA134 is wired as a non-inverting amplifier. The +/-4.5V split power supply required for the IC is obtained from a 9V PP3 battery using the circuit comprising of components D1. R6, R7.R8, C2 and C3. D1 is an LED which indicates power ON. Switch S1 can be used as a ON/OFF switch .Resistor R2 and capacitor C1 forms a high pass filter with corner frequency around 15KHz.POT R1 can be used as a volume controller. The load resistor R5 will stabilize the virtual ground and prevents any noise or distortion in the output, but the output will be DC coupled.
Circuit diagram.

pocket headphone amplifier circuit

Notes.

  • Assemble the circuit a good PCB.
  • The circuit can be powered using a 9V PP3 battery.
  • POT R1 can be used as a volume controller.

Comments
  • riya
    February 3, 2015

    can this circuit be used with wireless ir headphone

  • Talal
    March 19, 2014

    Hi Mr. Seetharaman:
    Good day, I’ve always loved your circuits and explanations, so I would like to ask about an amplifier circuit I assembled today.
    I used the tda2822 8 pins stereo circuit as in the datasheet, and connected it to two 1 inch 8 ohm speakers, and a 3.6v lithium battery and connected it to my PC/Mobile.
    But the sound is very loud and noisy when I turn down the stereo potentiometer (It works fine only on the highest resistance value) , so is it the 10k potentiometer (should I use 100K?) or is it lack of voltage? and if so should I use another amp. circuit that works better with 3.6v battery and what do suggest? or is it something else like capacitors (I used 1000uF instead of 470)
    Thanks a lot for your time and effort 🙂

  • melissa ono
    November 12, 2013

    i am looking for a circuit to make a headphone amplifier circuit suitable for mp3 ipods etc with these spefications
    Provide an improved sound quality over the un-amplified output of your MP3 player.
    • Have an input impedance of at least 100kΩ.
    • Have an output impedance of less than 100Ω.
    • Have a frequency response of at least 20Hz – 20kHz (this means that the lower limit
    should be 20kHz).
    • Have a volume control.
    • Operate from a PP3 battery (a connector to clip on to a PP3 battery will be provided).
    • You may optionally add a tone control or cross-feed. You may use transistors or
    operational amplifiers in your design.

  • Alex
    February 21, 2013

    Just a quick question, why is there a 15khz high pass filter on the op amp ? also i think the calculation comes out a a 15hz highpass filter ? why is this necessary ?

    • Seetharaman
      November 16, 2013

      The hi pass filter is set to 15KHz approx. Nothing above this is required for an audio amp. Infact frequency response beyond this can give you instability and other layout problems.

  • harsha
    March 24, 2012

    hi friends i have to do a mini project related to analog communications sub can any one suggest the projects related to that
    i have very less time so can u please suggest the circuits which are very easy and which are much useful

  • May 6, 2010

    Seerharaman dada, thanks you a lot .

  • seetharaman
    May 6, 2010

    I have given you the idea for the volume control. For stereo application you require 2 potentiometers or a single stereo potentiometer. one potentiometer slider to Pin7 of the IC, and the other potentiometer slider to Pin no6 of the IC.
    104 stands for 0.1uF.
    1uF = 1000nano farad
    1nano farad = 1000 Pico farad
    1uF = 1000000 Pf
    0.1uF = 100 nano farad (nF) = 100000 Pf..
    If you use a 47K potentiometer use around 47 K in series with the pot before connecting to card output, This should match the line impedance 100K. or use a 100K pot, which are freely available, without any additional resistance.

  • May 6, 2010

    Seetharaman dada,
    Thanks for your reply . I don’t understand first line . You are saying-“Above Circuit” . But which circuit- are you saying above OPA134 Circuit ? But I have built same as circuit from the diagram of IC DATA SHEET of TDA2822 .

    As your instruction, If I connect both channel (L+R) in Pin6, then it will be look like Bridge circuit (As Shown in the IC DATA SHEET). But I have stereo input . Can I ask- why will we input both channel in Pin6 ?

    I want to add a volume control (I mean VR) in the circuit . please tell me How can I do that ?

    And 0.1µF means 1000PF (0.1x100x100). That will be 10³ . Is my calculation right ?

    And as you are Indian , then you should be familiar with GADMEI external TV card . I am using this amplifier for this TV card to my headphone . I need to set the volume of TV card to “Vol1” . If I increase the volume to “vol2” , then the amplifier output becomes so noisy . That means- This input line is so high for the TDA2822 .

    So, I want to add an Resistance in input line . How much Resistor will I use for input Resistance ?

    – Thanks

  • seetharaman
    May 5, 2010

    Hi Digonto You connect C1 of the above circuit to Pin 7 (pin 6 for the other channel) of the IC TDA2822. C6 & C7 can be either type and should be 104PF (0.1) not 102(0.001 that is 1000PF)
    102 First two digit indicates the value and third is the multiplier as 10²
    103 First two digit indicates the value and third is the multiplier as 10³ etc
    Similar to colour codes but with numbers.

  • May 5, 2010

    Hello Seetharaman,
    As your advice I have built a mini headphone amplifier with TDA2822M today . I have built the circuit same as test circuit (Stereo) shown in the Data Sheet . I have used a 9V PP3 battery to power the circuit . Now I want to add a volume control in circuit . Where and how will I add the volume control ? Can u give me feedback or a diagram ?

    And for C6 & C7 0.1µF capacitors- which will I use- Is it 102PF (Ceramic disc) or 2A102J (polyester film)? I have used 102PF capacitor . Is it OK ?

    – Thanks

  • seetharaman
    March 7, 2010

    For the above application DIP8 pin TDA2822M FCI Semiconductor Dual Low-Voltage Power Amplifier in bridged mode is most suitable. You may refer to manufacturers application/datasheet. can work from 2 to 15 volt into 4to 32 ohms load. this ic is used in most walk-mans.

  • March 7, 2010

    thanks for the help, ill try to find the part 🙂

  • March 5, 2010

    Mate, i cant find OPA134 anywhere…is there a replacement for it? help asap

    • admin
      March 5, 2010

      reply to stex
      LF151 is possible a substitute for OPA134

  • stranger
    February 17, 2010

    the ic1 opa134 is very costly..any cheaper alternative?

  • January 11, 2010

    i want more info abt Pocket headphone amplifier and working of its circuit.

  • December 26, 2009

    thank u

  • Kiragga Geofrey
    December 25, 2009

    thanks for evry thing but i would like to inquire if i can get a circuit that inverts 3volts to 12volts.
    adding 2batteries of 1.5v to produce power that can light a 12volts bulb.
    thank you

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