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  1. audioguru2

    noise cancelling circuit

    If the opamp is simply biased at half the supply voltage with two resistors and a filter capacitor then a single supply can be used. You do show a preamp opamp (but with gain much too small) but it is inverting with a very low input resistance (1k produced by R4) so the mic signal is loaded down...
  2. audioguru2

    Is it a hartely oscillator??

    Hi Walid. Yes, because its coil is tapped and provides positive feedback to the base of the transistor. No, it affects the current in the transistor which changes the output power. It is simply a continuous carrier frequency without AM nor FM modulation. If something modulates the amplitude of...
  3. audioguru2

    RF coupling transformers

    IF transformers are old and are not used anymore. Higher performance and lower cost crystal filters and SAW (surface-acoustic-wave) filters are used for the past few years.
  4. audioguru2

    Question lng po mga Master Sir/Ma'am

    Sorry. We speak only in English on this website. There is another website with a similar name in the Philippines.
  5. audioguru2

    HiJack Public Speakers

    Most audio cables are shielded to block interference. Some audio cables are balanced to cancel interference. So your idea will not work.
  6. audioguru2

    noise cancelling circuit

    You do not place the mic inside the earphone cup because then it will try to cancel the wanted signal. It is mounted on the outside of the earphone cup so it hears the noise but does not hear the signal. You do not reduce the high frequencies from the signal, you cut high frequencies from the...
  7. audioguru2

    noise cancelling circuit

    The lousy old LM324 is horrible for audio. It is noisy (hiss), has crossover distortion and has trouble above only 2kHz. C4 in your circuit reduces frequencies above only 500Hz. You show an opamp driving headphones which might be impossible because an opamp has a low output current. Which type...
  8. audioguru2

    0-30V Stabilized Power Supply

    The TLE2141 opamp for U1 has a typical current of 3.5mA when warm and a max current of 4.5mA. The zener diode D8 adds 5.6mA to the current in U1 so its total current is 9.1mA to 10.1mA. Then the voltage across your R7 is 2.5mV to 2.7mV which is nothing. The input offset voltage of U1 is a max of...
  9. audioguru2

    0-30V Stabilized Power Supply

    What is the problem? The output voltage is supposed to be regulated when the current regulation is not reducing the output voltage. Does the warning LED for the current regulator light up when there is no load?
  10. audioguru2

    0-30V Stabilized Power Supply

    Hi Nemeszoli, How can pin 2 of U3 have a voltage when there is no load on the project? Pin 2 is connected to 0V by R7 that has no current in it. Maybe you have leakage current in your 0V printed wire. If C7 has "dielectric absorption" then there will be an output voltage when the voltage pot is...
  11. audioguru2

    0-30V Stabilized Power Supply

    The output voltage should not increase if it is set to one voltage. What is "the intensity variation is broken"?
  12. audioguru2

    question about symetrical swing

    A single transistor with a high voltage gain produces an extremely distorted signal if its output approaches anywhere near cutoff because its transconductance is very non-linear. Here is an example:
  13. audioguru2

    transistor biasing

    A 2N3904 transistor will melt if it has 100mA of current and a collector-emitter voltage higher than only 6.25V. if you want power then use a power transistor mounted on a heatsink. For the 2N3904, the datasheet spec's a minimum hFE of only 30 and a typical hFE of 150 at 100mA. Then it is too...
  14. audioguru2

    0-30V Stabilized Power Supply

    The LM317 reduces its max output current to only 150mA when its input to output voltage is high. An LM317 does not have adjustable current regulation. Instead it has simple abrupt current limiting at 1.5A to 2.2A when the input to output voltage is 15V or less. An LM317's output does not go down...
  15. audioguru2

    0-30V Stabilized Power Supply

    There are many cheap weak little power supply projects on the internet. Some work but many don't.
  16. audioguru2

    transistor biasing

    The 2N3904 can drive a collector resistor (not a load) with a current of 100mA but its current gain is less and it might melt. The range of current gain is guaranteed at a collector current of only 10mA. With a collector current as high as 100mA then its current gain is a minimum of only 30...
  17. audioguru2

    0-30V Stabilized Power Supply

    With a max output of only 300mA and a max voltage of only 25VDC then the two 2N3055 transistors can be a single TIP31 transistor on a heatsink that is not very big.
  18. audioguru2

    Led display Digital Voltmeter question

    I like new LCD not old LED voltmeters. I never use a voltmeter in the dark so the LCD display has good visibility.
  19. audioguru2

    0-30V Stabilized Power Supply

    A 2A transformer is also too small. Then the max current from the project will be only 1.4A DC. I have a graph that shows the amount of p-p ripple in a full-wave rectifier with a 60Hz mains and with various sizes of filter capacitors:
  20. audioguru2

    0-30V Stabilized Power Supply

    I don't know if you are making the original faulty circuit or which improved circuit. Since your transformer is so small then you can make a simpler low power circuit.
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