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  1. audioguru2

    Guitar Aplifier

    Why did you install the filter netwok? Audio amplifiers don't use one because they have a good power supply noise rejection ratio.
  2. audioguru2

    Guitar Aplifier

    C13 is the main filter capacitor for the power supply. You never want to connect anything in series with it. Adding a 47pF capacitor from the collector of Q3 to ground (not to its base because the base is used for negative feedback) will reduce high frequencies which will reduce the possibility...
  3. audioguru2

    0-30V Stabilized Power Supply

    This circuit is not designed for the high voltage you have.
  4. audioguru2

    0-30V Stabilized Power Supply

    Yes, if each power supply circuit is completely separate from each other with separate transformers.
  5. audioguru2

    0-30V Stabilized Power Supply

    Then the pre-regulation circuit will melt trying to dissipate up to 177W.
  6. audioguru2

    circuit distortion

    An opamp has extremely low distortion at low frequencies because its gain is extremely high which results in a lot of negative feedback. A TL07x opamp has 0.003% distortion at 1kHz with a load of 2k ohms or more, a 30V supply and an output of 6V RMS. Its gain is 1. Its open-loop gain at 1kHz is...
  7. audioguru2

    0-30V Stabilized Power Supply

    If the output is set to a low voltage or is shorted then the TIP142 will melt trying to dissipate 195W. Your supply voltage is so high that nearly every other part will also get too hot.
  8. audioguru2

    Guitar Aplifier

    The ground of the preamp can connect to the input ground of the power amplifier because the preamp uses a very low supply current.
  9. audioguru2

    Guitar Aplifier

    I notice that the power amplifier is inverting so capacitive coupling through the air from the output to unshielded wires at the input cause negative feedback, not positive feedback. oscillation occurs with positive feedback so that is not the cause of the oscillation. Since you have the input...
  10. audioguru2

    Guitar Aplifier

    Then the volume control wiring or the input wire are not shielded and are picking up interference from the power supply wiring or from the output wire. Or maybe you did not connect the grounds as a "star".
  11. audioguru2

    Guitar Aplifier

    Screened cable is shielded audio cable that is used to connect stereo components together. It stops interference and feedback. The volume control should be connected with it and the input from the guitar should use it. The power amplifier should be disconnected from the input circuit to see if...
  12. audioguru2

    Fm transmitter

    Electret microphone preamp circuits are on my hard drive but you can find them on Google. Pre-emphasis circuits the same. Voltage regulator circuits the same. Do it.
  13. audioguru2

    Help with lights controlled by audio

    You need an Audio Spectrum Analyser circuit. It is fairly complicated to make by yourself even if it is already designed. Then you must design and make many output driver circuits. I have seen some that are controlled by a micro-controller. It needs to be programmed.
  14. audioguru2

    low cast emergency automatic light

    You are correct, the circuit does not work. Nothing turns on the BD140 transistor. Many circuits posted here from that author do not work.
  15. audioguru2

    Want a 4400uF 50WVDC Capacitor

    For a power supply you want filter capacitors with the highest value you can afford or for a certain physical size. Electrolitic capacitors have a wide tolerance of their value. The minimum value of a 4700uF capacitor might be 3760uF. A 4400uF capacitor might be only 3520uf and have a ripple...
  16. audioguru2

    Fm transmitter

    Simple circuits never work well because important things are missing. This one also needs to have a regulated power supply because it is tuned by voltage. Without a regulated voltage the frequency will change as the battery runs down. With a regulated power supply and a mic preamp with...
  17. audioguru2

    Fm transmitter

    A condenser mic needs a 48V supply. Instead, why not use an inexpensive electret mic that has the 48V built-in? The electret mic meeds to be powered through a 10k resistor from a voltage of 3V to 12V that is filtered. The simple transmitter circuit needs to have an electret mic preamp circuit...
  18. audioguru2

    0-30V Stabilized Power Supply

    The TL081 opamp has the problem called "Opamp Phase Inversion" where its output suddenly goes high when its negative power supply voltage becomes close (within about 3V) to its input voltages which happens in this project when the power is turned off. Q1 shorts the output of U2 to 0V to prevent...
  19. audioguru2

    resonant filtering

    An ordinary power supply is not resonant. It rectifies the 50Hz or 60Hz from the transformer and filters out the low frequency ripple. A high frequency switching power supply is resonant so it can efficiently stepup the voltage or efficiently stepdown the voltage with an inductor.
  20. audioguru2

    circuit distortion

    Very old opamps like the 741 and LM324/LM358 have a high noise level. They also have different but high distortions. The main distortion for the LM324/LM358 is crossover distortion because they are biased for low power. The bias current is so low that it causes crossover distortion. Their...
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