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  1. audioguru2

    Making LEDs turn on at a certain resistance

    Hi Ribrab, Welcome to our forum. ;D It looks like you want the LEDs to light one after the other, like a bargraph. A pot won't do it, and its value of 100k if far too high to provide enough current for a single LED to be seen. You could do it with a multi-position switch. You need a bargraph IC...
  2. audioguru2

    Working of a PLL

    The datasheet for the LM567 explains how it works pretty well. There is an article about PLL's in our Articles section.
  3. audioguru2

    Input signal for LM3915. need help.

    Hi Ryeeson, I don't use special software to make or modify schematics. I just copy and paste stuff using Microsoft Paint. Your circuit will have so much gain that it will come out of its wing-wang! You were using Ron Elliott's mic preamp circuits for FM transmitters that have an awful lot of...
  4. audioguru2

    Please recommend the alternative of this IC

    Take one from a trashed TV.
  5. audioguru2

    want to make an audio amplifier

    Hi Shaiq, Audio power amplifiers use usually complementary power transistors operating as emitter-followers at their output to provide enough current and symmetry. DC negative feedback is used to provide a stable DC operating voltage and AC negative feedback is used to create a certain voltage...
  6. audioguru2

    pramplifier circuit

    Hi Mughal, I'm glad that the preamp works perfectly. ;D The opamp is low noise, wide bandwidth and very low distortion for an audio preamp. It operates as a non-inverting opamp circuit with the ratio of the resistance of the pot and R4 providing negative feedback determining its AC voltage gain...
  7. audioguru2

    Switching idea

    Yes, I see the latching effect of the Schmitt-trigger now. On the very 1st day of my engineering job at Philips I was shown the datasheet of a silicon transistor that showed its Absolute Maximum Ratings. The emitter-base junction was rated at 5V. I was told NOT TO GO THERE! The emitter-base...
  8. audioguru2

    0-30V Power Supply - doesn't work

    Can't you see a PNG file type? Here it is as a GIF:
  9. audioguru2

    0-30V Power Supply - doesn't work

    A copy of a copy isn't the same as the original, is it? Check all parts values with the parts list in our projects section. Then your project will probably work as poorly as others that were built. Then look at the topic about fixing it and making it more reliable in our forum. I recommend this...
  10. audioguru2

    Switching idea

    Hi Mr. Heckles, Your Schmitt Trigger comparator isn't doing anything. It just repeats the output of the window comparator. The comparators don't have any connection to the PNP transistor. The PNP transistor will have its base-emitter junction blown if the Signal voltage exceeds 12.7V (forward...
  11. audioguru2

    0-30V Power Supply - doesn't work

    Hi Rubick, Disconnecting Q1 made the output voltage high so the negative 5.6V supply must not be working. This sketch shows its parts and how they work with each half-wave from the transformer.
  12. audioguru2

    Want to make Auto Range Power Supply.

    If you want to make the 0-30V power supply on this site to work with different AC input voltages then you will need to add a high-power switching AC-DC power supply to provide it with about 40V at 3A to replace the project's transformer and rectifier.
  13. audioguru2

    0-30V Power Supply - doesn't work

    Hi Rubick, Welcome to our forum. ;D U2 would get hot if Q1 is conducting when it shouldn't. Also, if Q1 is conducting then the output voltage will be very low like your project. Check Q1, R13, R14 and the parts that make the negative 5.6V supply.
  14. audioguru2

    Want to make Auto Range Power Supply.

    Many electronic products have a switching power supply that works with AC input from 85V to 250V.
  15. audioguru2

    Input signal for LM3915. need help.

  16. audioguru2

    interesting little project

  17. audioguru2

    KA7500B

    All details are in its datasheet. Go to www.datasheetarchive.com and enter its part number.
  18. audioguru2

    Working on 7-Seg Up/Down Counter. Bounce problem with push button.

    It sounds like the PLD needs a 0.1uF ceramic disc and a 10uF or 100uF electrolytic supply bypass capacitors connected right at its supply pins.
  19. audioguru2

    increasing the sensitvity of cell phone mic

    It's an ordinary mic preamp circuit with adjustable gain. 2 or 3 transistors would also work but its circuit would be bigger. How can a short circuit amplify a microphone? Wouldn't a very sensitive mic pickup all kinds of background noises, overload very easily with "normal" sounds and amplify...
  20. audioguru2

    increasing the sensitvity of cell phone mic

    If your cell phone has a jack for a headset mic, then make a preamp for your own separate mic. My cell phone detects if I have an external earphone plugged in 'cause it uses its cord as an FM radio antenna that doesn't work without the cord plugged in.
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