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  1. Audioguru

    Op-Amp Help

    Look again. V1, V2 and V3 are not in parallel, they are completely separate from each other and they have different levels. They connect to their own input resistor of the circuit.
  2. Audioguru

    LM358 one opamp fails Please sugest what to do..

    Your schematic is not finished yet since the resistor values are not printed on it. The LM358 cannot be damaged in your circuit because there is no input voltage. The datasheet says the input must never be more negative than -0.3V or more positive than +32V. The datasheets are powered by 8V. Is...
  3. Audioguru

    How Does One "Provide" A Different Level Of Current?

    60W/12V= 5A. but only when the light bulb is at its normal very hot operating temperature because an incandescent light bulb draws a much higher current before its filament is 2000 degrees C. A DC motor's current is also much higher before it is up to its normal speed.
  4. Audioguru

    Op-Amp Help

    I told you already, at V1, V2 or V3 which are the inputs to the circuit.
  5. Audioguru

    A radio from 1920 goes to 2017 !

    You are in France, I am not. I buy good quality products that are available here. I avoid buying cheap Chinese no-name-brand junk from ebay or Amazon. There are other cheap Chinese auction sites I also avoid (Alixxxx).
  6. Audioguru

    Op-Amp Help

    V1, V2 and V3 are the inputs to the entire circuit. You NEVER(!) look at the (-) input of an opamp because its signal is cancelled by the negative feedback when the output is not clipping.
  7. Audioguru

    Can you check over this Circuit?

    On another forum we described this old circuit from India as a nightmare of errors. It even says the mic is a "condensor" type which will not do anything in this circuit. The mic is supposed to be called an electret mic.
  8. Audioguru

    Op-Amp Help

    You calculated that the output should be 27.5V RMS. But the scope shows peak-to-peak (Pk-Pk) that is 2.282 times less. It is a coincidence that the numbers are almost the same. Don't you know about clipping? When the output tries to be 27.5V RMS x 2.828= 77.77V peak-to-peak but the output swing...
  9. Audioguru

    Op-Amp Help

    You are not supposed to look at the (-) input of the opamp because the signal is almost completely cancelled by the negative feedback when the opamp is not clipping. But your opamp is obviously clipping like crazy with such a high input level.You are supposed to look at the input of the entire...
  10. Audioguru

    How Does One "Provide" A Different Level Of Current?

    The person who wrote the wrong things does not know anything about electricity. It should say "do not apply excessive voltage to the motor". Does the manual say the voltage that should be used?
  11. Audioguru

    A radio from 1920 goes to 2017 !

    My good sounding 2.1 stereo DEE-VICE for the beach used National Semi LM2896 bridged amplifier ICs with bootstrapping. They were powered by six C size Ni-Cad battery cells producing about 7.5VDC. I have never used a lead-acid battery for anything except in my car.
  12. Audioguru

    Understanding N-Channel MOSFETs

    All new people are confused with the threshold voltage of a Mosfet. It is when the current in the Mosfet is very low, usually only 0.25mA. I tell the new people that the threshold voltage is when the Mosfet is almost turned off, not almost turned on. The triode or saturation modes of Mosfets...
  13. Audioguru

    A radio from 1920 goes to 2017 !

    The bluetooth speaker uses a cheap single midrange speaker that produces no bass and no sizzling highs but has a normal peak in its response at a shrieking 5kHz. The cheap Chinese amplifier has its TDA7492 stereo IC with a supply of 9V if the battery is brand new and only one channel drives the...
  14. Audioguru

    Wiring together LED lighting for a display

    The original Chinese batteries were probably weak (full of rice) and could not produce more than 20mA. Calculate resistors to limit the current to 20mA, not 50mA.
  15. Audioguru

    Wiring together LED lighting for a display

    I betcha the "6V" AC-DC adapter voltage will be much higher than 6V with the puny load of 50mA. Maybe 9V or 10V? Then the current will be 105mA and the LEDs will fail soon and the resistor will get so hot that it might glow and smoke. 50mA is too high for ordinary LEDs that are rated at 20mA...
  16. Audioguru

    Solar panel.

    The meter is not fast enough to show the dropped voltage when the motor is not running yet so is simply a low resistance of its coils of wire. The dropped voltage causes the motor to stumble when starting. When it is running a few ms later it runs fine at a higher voltage that the meter is...
  17. Audioguru

    A radio from 1920 goes to 2017 !

    Do not buy pieces on the internet at random without knowing the specifications the project needs. It seems that this project needs experience about how to do it that you do not have.
  18. Audioguru

    Op amp unexpected results

    The design of a 741 opamp is 49 years old and it was designed to use a 30V power supply. Some 741 opamps will work when the power supply is as low as 10V but none will work with only 4.5V. Your 4.5V battery will soon drop to 3V or less. You show a transistor with no part number and its pins are...
  19. Audioguru

    RC Low pass filter problems

    A resistor in series then a capacitor to ground at the input of the subwoofer amplifier might be designed to reduce 100Hz a little (-3db). Then 200Hz is reduced a little more and 400Hz is reduced a little more but still can be clearly heard, even though the frequency is much higher than...
  20. Audioguru

    Passive Frequency Filter with Cut-off negative part of the sine wave

    A bandpass filter does not select the band of frequencies you want and block the frequencies you don't want. It selects the middle of the band at full level then reduces the edge frequencies a little. The frequencies above and below are reduced, only when the frequencies are fairly distant from...
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