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  1. audioguru2

    Difference between rms and PMPO

    Hi Shamin, The power rating of an audio amplifier is supposed to be with its built-in power supply (if it has one, or its supply voltage should be mentioned), all channels operating continuously with a sine-wave from 20Hz to 20kHz and at low distortion below clipping. The power rated will be...
  2. audioguru2

    Need sugestions about virtual ground or symetric supply for OPAMP

    Hi Wellington, The opamp is just a follower of the resistor divider that has a capacitor to ground. Some opamps oscillate if the output has a capacitor load. I hear an odd form of distortion on the ambiance channel of your Troubled Waters clip. It sounds like buzzing when the brass horn...
  3. audioguru2

    Need sugestions about virtual ground or symetric supply for OPAMP

    Hi Wellington, I am glad that you discovered the cause of your distortion. ;D Your circuit doesn't need the very high power virtural ground circuit with the old CA3140 opamp and high current darlington transistors. An ordinary opamp by itself and made into a follower as shown by Analog Devices...
  4. audioguru2

    white led

    Who makes that lens? Does it work? Will it work well with a Luxeon LED? Philips probably make a suitable lens for their Luxeon LEDs.
  5. audioguru2

    Electronic Stethoscope 2

    The circuit uses two 9V batteries One makes the positive supply and the other makes the negative supply. You need to have two separate power supplies to make the two voltages.
  6. audioguru2

    Problem With Ultrasonic Motion Detector

    Use a CD4060oscillator/divider IC. It can't oscillate as high as 4MHz and it divides the frequency in binary instead of by 10, but if you can get a crystal frequency of 2.56MHz,or 1.28MHz it will produce 40kHz.
  7. audioguru2

    Two PCBs off of one power source

    The MC34119 will get very hot with a 6V supply and an 8 ohm speaker. It will waste a lot of battery power. Use an LM386 amplifier IC instead. Connect four diodes in series to drop 6V down to 3.2V.
  8. audioguru2

    0-30volts Lab power supply

    Pots are made only in certain resistance values and their resistance has a tolerance of about 20%. So you won't get one that is 294 ohms. Maybe 200 ohms and 500 ohms are the closest. Use a multi-turn pot instead like Ante uses.
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    The opamp has a typical voltage gain of 200,000 at DC, so any very small change in the output voltage due to load current is reduced to nearly nothing.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    The voltage setting pot has its voltage (0V to 11.2V) amplified by opamp U2. Its only negative feedback path is R12 and R11 which set its voltage gain to 3.074.
  11. audioguru2

    Electronic Stethoscope 2

    Pin 8 of the TL072 is connected to pin 6 of the LM386 on your pcb and is labelled "+9V" correctly. You measured different voltages so maybe the printed copper track is broken. Measure the copper with an ohm-meter to see where it is broken. Measure the voltage of the positive battery while it is...
  12. audioguru2

    0-30volts Lab power supply

    If 10k ohms gives 34V then 10k/34= 294 ohms gives 1V. It won't be accurate since pots have a tolerance of 20%.
  13. audioguru2

    Are datasheets important?

    It might be very intermittent with a load current 100 times its recommended maximum. Yesterday it worked. Today it didn't work and blew its fuse. Tomorrow it might work or it might not work. The CD4047 IC  has an internal resistance that is hundreds of ohms so the oscillator might work without a...
  14. audioguru2

    Are datasheets important?

    The author of the "500W" inverter project selected a 4.7uF capacitor for the oscillator at random. R&D engineers calulate parts values properly. I selected 100nF by calculating it properly, and knowing that a nonpolar and an accurate 5% one is inexpensive. My calculated 47k resistor makes...
  15. audioguru2

    0-30volts Lab power supply

    The 10k resistor provides an output voltage range of from 0V to about 34 (but the project can't go that high). Since 100 ohms is 1/100th of 10k then its fine tuning range is from 0V to only 0.34V. The 10k pot doesn't need to be changed. This is the voltage setting pot which is a voltage...
  16. audioguru2

    Electronic Stethoscope 2

    Hi Soly, Your circuit doesn't have a positive 9V supply: Pin 8 of the TL072 is supposed to be +9V. Yours is nothing. Pin 6 of the LM386 is also supposed to be +9V. Yours is very low at only +2.7V. The above pins are connected together and should measure exactly the same voltage. Yours have...
  17. audioguru2

    Are datasheets important?

    Nobody has posted in a forum here that the original faulty "500W" inverter project works. This forum is for discussing THEORY. This topic discusses the wrong way its oscillator parts were chosen. Texas Instruments recommends a resistor with a minimum value of 10k ohms in their datasheet for the...
  18. audioguru2

    Dual Volument Control (Rotate type) B50K 7-legged

    The manufacturer's datasheet would show what is the 7th pin. I think it might be a ground terminal for its metal parts.
  19. audioguru2

    0-30volts Lab power supply

    Hi Pier, Of course you can add a fine tuning pot. Just add it in series with the existing pot. Make it have a value less than the existing pot. You might need to reduce the value of the existing pot a little.
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Omni, How can your power supply have an output voltage of 30VDC with some current, with a 24VAC transformer that makes rectified only 32VDC? Isn't the output full of ripple if the voltage is higher than 25VDC and the current is more than about only 2A? How can the 24VDC/3A (72VA)...
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