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    Ear headphone with low sound

    hi every one
    i want to amplifi audio signal from phone
    i have ear headphone with low sound
    to do that i want to use smd dual op amp
    1/2 for right the rest for left
    vin =0.7v , power in= 1mw
    gain=3
    power source : 2 coin cell 3v
    speaker = 600 ohm (from some set)
    could it work without lead from op amp to another
    and is there any error
    picture's attached
    any advise are thankful
    Last edited by bassa; 9th September 2018 at 15:02. Reason: remove font size

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    Re: Ear headphone with low sound

    It might work but I would advise capacitors to couple the input signal and possibly a load resistor across the input to keep the phone happy. It also depends what op-amp you plan to use. Some are only for very low level signals or have very restricted bandwidth.

    Brian.
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    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.


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    Re: Ear headphone with low sound

    Hi,

    I agree with the capacitors.
    I recommend to use a dedicated earphone amplifier. Usual Opamps may have problems to drive that low impedance with output close to the supply rails.

    Maybe use class D amplifier with low pass filter.

    Klaus
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    Re: Ear headphone with low sound

    Quote Originally Posted by betwixt View Post
    It might work but I would advise capacitors to couple the input signal and possibly a load resistor across the input to keep the phone happy. It also depends what op-amp you plan to use. Some are only for very low level signals or have very restricted bandwidth.

    Brian.
    thanks mr Brian
    ok i will use capacitors and load resistor
    i want to use LM158 but from it data sheet
    Input Voltage ( -0.3V to +32V )
    but my Input Voltage go to (-0.7)
    sorry im confuse about -0.3 and -0.7
    is -0.3v mean the lowest input voltage ?



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    Re: Ear headphone with low sound

    Quote Originally Posted by KlausST View Post
    Hi,

    I agree with the capacitors.
    I recommend to use a dedicated earphone amplifier. Usual Opamps may have problems to drive that low impedance with output close to the supply rails.

    Maybe use class D amplifier with low pass filter.

    Klaus
    thanks mr Klaus
    ok i will do google search for dedicated earphone ic and after read it data sheet i will post my effort
    about class D amplifier is it will be 2 unit ?
    one for right and second for left ?



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    Re: Ear headphone with low sound

    Hi,

    Because humans have two ears, I assume most earphone amplifiers come with two channels.

    Klaus
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    Re: Ear headphone with low sound

    Hi,

    "Wide Power Supply Range:
    Application areas include transducer amplifiers, dc
    – Single Supply: 3V to 32V gain blocks and all the conventional op-amp circuits
    – Or Dual Supplies: ±1.5V to ±16V"

    If the input only goes to -0.7V on +-3V, you're fine. The -0.3V means not exceeding an additional +-0.3V beyond the +-supply rails on the inputs.

    I'm not sure but I'd check that the output can actually go to +-2.8V, if not then extend the supply or lower the output if possible, or just switch to a rail-to-rail (input and) output op amp. One of the experts here will know better if the op amp fits the input and output range.

    LM158



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    Re: Ear headphone with low sound

    sorry you say: Maybe use class D amplifier with low pass filter.
    my project have 2 input so i guess you mean classic old class D amplifier one input one output
    not ic based on class D amplifier technology
    Click image for larger version. 

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    Quote Originally Posted by KlausST View Post
    Hi,

    Because humans have two ears, I assume most earphone amplifiers come with two channels.

    Klaus
    someone set behind keyboard wait for reply from he's admire teacher
    reply come that way!!!!
    sadly,,,
    sorry for being not know humans have two ears.



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    Re: Ear headphone with low sound

    Hi,

    I assume there are class D earphone 2 channel ICs.
    Did you do a search? At manufacturers and/or distributors...

    Klaus
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    Re: Ear headphone with low sound

    Quote Originally Posted by d123 View Post
    Hi,

    "Wide Power Supply Range:
    Application areas include transducer amplifiers, dc
    – Single Supply: 3V to 32V gain blocks and all the conventional op-amp circuits
    – Or Dual Supplies: ±1.5V to ±16V"

    If the input only goes to -0.7V on +-3V, you're fine. The -0.3V means not exceeding an additional +-0.3V beyond the +-supply rails on the inputs.

    I'm not sure but I'd check that the output can actually go to +-2.8V, if not then extend the supply or lower the output if possible, or just switch to a rail-to-rail (input and) output op amp. One of the experts here will know better if the op amp fits the input and output range.

    LM158
    thanks mr d123
    seriously you helped me
    i want very few component and lite circuit
    so i plan to use coin cell
    first
    a rail-to-rail
    if not
    i have to lower the output

    - - - Updated - - -

    Quote Originally Posted by KlausST View Post
    Hi,

    I assume there are class D earphone 2 channel ICs.
    Did you do a search? At manufacturers and/or distributors...

    Klaus
    from post #5
    thanks mr Klaus
    ok i will do google search for dedicated earphone ic and after read it data sheet i will post my effort
    about class D amplifier is it will be 2 unit ?
    one for right and second for left ?



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    Re: Ear headphone with low sound

    You want the 0.7V RMS amplified 3 times so the output must be 5.94V peak-to-peak.
    Don't use a lousy old LM158 because it has crossover distortion and its output swing will be much less than the 6V p-p required so it will produce horrible clipping distortion.

    I think any amplifier will not produce a rail-to-rail output swing when loaded with 600 ohms. Then increase the supply voltage or reduce the input and output levels.
    I thought about a PAM8403 stereo class-D little amplifier but it is designed for a 5V supply and your 6V is too high for it.



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    Re: Ear headphone with low sound

    Quote Originally Posted by Audioguru View Post
    You want the 0.7V RMS amplified 3 times so the output must be 5.94V peak-to-peak.
    Don't use a lousy old LM158 because it has crossover distortion and its output swing will be much less than the 6V p-p required so it will produce horrible clipping distortion.

    I think any amplifier will not produce a rail-to-rail output swing when loaded with 600 ohms. Then increase the supply voltage or reduce the input and output levels.
    I thought about a PAM8403 stereo class-D little amplifier but it is designed for a 5V supply and your 6V is too high for it.
    thanks mr Audioguru
    i can do Switching Power supply unit that use XL6009
    and search for another op amp
    but do Switching noise here ignorable ?
    also dose coin cell suit for Switching ?
    so if Switching is not recommended i will reduce gain from 3 to 2



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    Re: Ear headphone with low sound

    Quote Originally Posted by burai View Post
    i want very few component and lite circuit
    This class D amplifier is made from a 555 timer IC. It's simple, inexpensive and useful to experiment with.
    The 555 is configured as a pulse generator. An audio signal is applied to the 'control' pin, causing the duty cycle to grow or shrink.
    The output is PWM. By filtering it becomes a close match to the original audio.

    Click image for larger version. 

Name:	555 is class D amplifier LC 2nd-order fil 60 ohm load gets 3V sines.png 
Views:	6 
Size:	19.4 KB 
ID:	148945



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    Re: Ear headphone with low sound

    Quote Originally Posted by BradtheRad View Post
    This class D amplifier is made from a 555 timer IC. It's simple, inexpensive and useful to experiment with.
    The 555 is configured as a pulse generator. An audio signal is applied to the 'control' pin, causing the duty cycle to grow or shrink.
    The output is PWM. By filtering it becomes a close match to the original audio.

    Click image for larger version. 

Name:	555 is class D amplifier LC 2nd-order fil 60 ohm load gets 3V sines.png 
Views:	6 
Size:	19.4 KB 
ID:	148945
    thanks mr BradtheRad
    it will be my next option
    if Switching Power supply not work

    - - - Updated - - -

    thanks every one

    - - - Updated - - -

    thanks every one



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    Re: Ear headphone with low sound

    The minimum supply for a 555 is 4.5V so even a 6V battery will fail soon.
    The output of a 555 does not swing anywhere near rail-to-rail.



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    Re: Ear headphone with low sound

    picture's attached
    Interested to know the mapping between these two pictures. Is differential Input of 0.7V is mapped to Left/Right of the universal 3.5mm Jack?
    Your life is all about ΔΣ, the narrow you estimate it, the precise it is ...



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    Re: Ear headphone with low sound

    Quote Originally Posted by Audioguru View Post
    I thought about a PAM8403 stereo class-D little amplifier but it is designed for a 5V supply and your 6V is too high for it.
    i read PAM8403 data sheet
    Absolute Maximum Ratings : Supply Voltage =6v
    how about make voltage divider and stay at 5v?
    file Attached
    - - - Updated - - -

    Quote Originally Posted by ashrafsazid View Post
    Interested to know the mapping between these two pictures. Is differential Input of 0.7V is mapped to Left/Right of the universal 3.5mm Jack?
    right to ground ~= 0.7v
    left to ground ~= 0.7v



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    Re: Ear headphone with low sound

    The datasheet for the PAM8403 recommends a max supply of 5.5V. Your coin batteries will produce 6.4V when new.
    You can use a voltage divider to reduce the battery voltage only if the current in the divider is very high that will kill your batteries in a few minutes because a voltage divider that powers something that has a variable current is a poor voltage regulator.
    Its inputs are not differential, each amplifier is bridged so the outputs are differential. The bridged outputs cannot drive headphones that have a ground, coupling capacitors can feed half the bridge to each headphone.


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    Re: Ear headphone with low sound

    Quote Originally Posted by Audioguru View Post
    The datasheet for the PAM8403 recommends a max supply of 5.5V. Your coin batteries will produce 6.4V when new.
    You can use a voltage divider to reduce the battery voltage only if the current in the divider is very high that will kill your batteries in a few minutes because a voltage divider that powers something that has a variable current is a poor voltage regulator.
    Its inputs are not differential, each amplifier is bridged so the outputs are differential. The bridged outputs cannot drive headphones that have a ground, coupling capacitors can feed half the bridge to each headphone.
    thanks you
    i decide to use one of pam8xxx
    and forget the circuit from post#1
    the main problem is the power source
    it toke me in new way by use
    mini Rechargeable battery »» Switching Power unit
    and stabilize the volt



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