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  1. Audioguru

    4.5 volt to 12volt

    I think the buck converter does not detect enough output current so it goes into burst mode with the output turning on and off.
  2. Audioguru

    4.5 volt to 12volt

    An LED driver is usually constant current then it adjusts its own resistance. Set the LED driver's current for the brightness you want and use as many LEDs in series in each string as their max forward voltage and the minimum output voltage of the LED driver allow.
  3. Audioguru

    Design of multistage audio amplifier

    1W into 12 ohms is (square root of 1W x 12 ohms) =3.464V RMS. The peak voltage is the RMS voltage x the root of 2. Note that the root of 2 is 1.414 and 1.414 x 2= 2.828, not 2.484. 3.464V RMS x (1.414 x 2)= 9.8V peak-to-peak. The total gain needed= 9.8Vp-p / 20mVp-p= 490 times. If the first two...
  4. Audioguru

    Design of multistage audio amplifier

    My typo said 121V but it should be 12V. An amplifier that drives both wires of a speaker (H-bridge) is called Bridged or Bridged-Tied-Load. Most car radio amplifiers (14W into 4 ohms when the battery is 13.2V) are like that.
  5. Audioguru

    Design of multistage audio amplifier

    Since the peak voltage of a sinewave is 1.414 times the RMS then peak-to-peak is 2.848 times, not 2.484 times. The output push-pull emitter followers have a voltage loss and their biasing also has a voltage loss. The output stage would need at least 12VDC, less if bootstrapping is used.
  6. Audioguru

    Design of multistage audio amplifier

    You do not want any DC current in a loudspeaker. Amplifiers usually use a push-pull output and feed audio to the speaker through a coupling capacitor or the output stage uses a power supply with plus ands minus voltages. Most of us would use a power amplifier IC that is fed from an opamp or...
  7. Audioguru

    2-way mic switch with LED channel indicators

    If you are using electret mics then they are powered with DC and will make a POP if disconnected or connected. You could use a circuit to ramp down their signal, switch, then ramp up the signal. Do the opposite to the other mic.
  8. Audioguru

    The Alesis M1 Active Mk2 Problem - capacitors dying from resistors

    The schematic of the amplifier show that R3 and R4 feed the "mute" pins of the amplifier ICs with a low current.
  9. Audioguru

    2-way mic switch with LED channel indicators

    Most switches use high current silver plated contacts that fail soon with the very low signal level from a microphone. Use a switch with gold plated contacts that are designed for low levels. They cost the same as switches with silver plated contacts. Switching electret mics will cause very...
  10. Audioguru

    The Alesis M1 Active Mk2 Problem - capacitors dying from resistors

    The schematic "Cannot be downloaded securely". My pc does not know what kind of file type it has. Maybe it should be a PDF.
  11. Audioguru

    confused about full bridge rectifier

    The resistance of the coil is probably very low since it is simply a piece of wire. Then you can calculate the very high DC current. You also need to measure the resistance of the meter leads so that it can be subtracted from the resistance measurement of the coil.
  12. Audioguru

    confused about full bridge rectifier

    Of course the diodes will burn up when the DC current in the coil is too high. I cropped the schematic and turned it around.
  13. Audioguru

    Subwoofer

    Many Logitech 3 speakers sound systems have a small woofer that has the amplifier built into it. The woofer speaker is too small and too cheap to play deep subwoofer sounds but you can connect it to another amplifier to hear it.
  14. Audioguru

    Identifying correct LED replacement

    Many colored LEDs are in a clear housing that has no color. A white LED usually has a yellow phosphor on top of the LED that looks yellow when it is not turned on.
  15. Audioguru

    Wired power for battery tools

    120V electricity is a sinewave that alternates and goes from 0V to a peak voltage then to 0V again and to the alternate peak polarity. The 18V is an average voltage of half the sinewave that goes from 0V to the peak voltage of 1.414 times the average voltage, over and over. 18V x 1.414= 25.5V...
  16. Audioguru

    need help for my circuit

    The datasheet for every transistor shows Absolute Maximum allowed voltages and currents. The reverse-biased emitter-base of a transistor is always rated at a maximum allowed voltage of 5V or 6V. A series resistor limits the current, not the voltage.
  17. Audioguru

    need help for my circuit

    Since your supply voltage is 12V which is much higher than the 5V maximum allowed Veb breakdown voltage of the transistors as I showed earlier, then maybe the transistors are breaking down and dimly lighting the LEDs. Then the transistors are slowly being destroyed.
  18. Audioguru

    need help for my circuit

    I am showing your wrong circuit again and explaining its errors. I show the correct circuit again. If the resistor and capacitor values are exactly the same, and the transistors have identical specs then the outputs will be perfect squarewaves with on times identical to off times. A CD4047 IC...
  19. Audioguru

    need help for my circuit

    Your Q3 is always turned on which always turns Q1 off, then they both are not needed. I do not see how your circuit works since it is completely different to the normal circuit.
  20. Audioguru

    need help for my circuit

    Your circuit will not work. Here is a common circuit that works, and a warning about damage if the supply voltage is higher than about 6V without using protection diodes.
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