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  1. audioguru2

    RC time constant

    Kevin, Your 2nd link doesn't work. The linearity of an AC signal isn't affected by an RC time constant. A highpass RC time constant reduces the level of low frequencies and a lowpass RC time constant reduces the level of high frequencies. The frequencies reduced in level remain linear.
  2. audioguru2

    transistors

    Hi Kevin, Have you seen the distortion of a transistor with a pure voltage input on a 'scope? It's really awful. Sounds worse than it looks. You must use negative feedback to improve it or reduce the input level.
  3. audioguru2

    Fet driving question

    Of course, the input of a Mosfet is a fairly high value capacitor. Divide the input voltage or the input frequency? Why? Why not just use a driver with a high output current rating so it can charge and discharge the Mosfet's input capacitance quickly? If you make a signal attenuator with...
  4. audioguru2

    transistors

    Hi Prateek, No conflict. With a very high gain, an amplifier can use more negative feedback to reduce the distortion and allow increased input. Negative feedback can be from an emitter resistor or from feedback directly to the input. ;D
  5. audioguru2

    tan-timers wanted to buy

    RED has informed me that only Motorola IC's worked in his Plants Watering Project. He didn't say what happens when the 3V battery's voltage drops over its life, but their guaranteed minimum is 3V. My project works with anybody's IC and its oscillators still work (but of course not the LED) when...
  6. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, Don't buy special stuff in local stores, order nearly anything online. I'm painting my plane the colour "Red Hot" right now, to make it extra ugly. It's styrofoam with bamboo spars, so I hope the paint (deluxe acrylic) will make it stronger. ;D I'll have an empty phoney "radio...
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ta, He, he. ;D ;D I knew you would ask what size. I could crunch some numbers, select a suitable one, then you'll say you can't get that one. Use a fan with two of your existing heatsink (no mica, use grease) like Thomas says. Make it variable speed like my pc and like some hi-end audio amps...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ta, OOps, your output transistors melted! :( Just think how hot the original project's single output transistor would get. Your heatsink (only one?) is way too small for such a powerful project like this one. I would use your 15x10cm heatsink for about 15 to 20W. Since your faulty project...
  9. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, Why? They are completely different animals: 1) The BZX79C5V6 is rated at 5.6V, while the 1N4735A is rated at 6.2V. 2) The BZX79C5V6 is rated and tested at 5mA, while the 1N4735A is rated and tested at 41mA. 3) The BZX79C5V6 has a low differential resistance at low currents for good...
  10. audioguru2

    Don’t over rev your Intel!

    The variable speed fan in my new pc will blow away any smoke. ;D
  11. audioguru2

    Keys finder circuit

    Hi Lapsap, Like I said before, the circuit is designed to respond to a fizzle sound, not a whistle sound. I can't make a whistle sound anywhere near as high as the 4kHz resonant frequency of my piezo transducer. I don't know what is a fizzle sound, but it needs to be at the resonant frequency of...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ta, Since the current regulator's LED turns on, then the output pin 6 of U3 must be going low like it should, therefore D9 should be pulling down the input pin 3 of U2, therefore U2's output should also pull down to reduce the output current by reducing the voltage. Maybe Q2 doesn't have a...
  13. audioguru2

    Don’t over rev your Intel!

    It's for overclockers, and their liquid nitrogen cooling. My new PC operates fast enough the way it was made. ;D
  14. audioguru2

    transistors

    Hi Prateek, I don't think a high beta (current gain) makes a transistor amplifier have a high voltage gain. A darlington transistor has an extremely high beta, and its gain is about the same as an ordinary transistor. A high beta transistor in a common-emitter stage has a higher input impedance...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ta, You can use your sound card as a 'scope to see hum on the project's output when you turn-up its voltage with full load. With your 24V transformer I think its max output with full load is about 26V and you will see ripple at higher voltages. I would like to know how good is its voltage...
  16. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Sorry to be off-topic for a minute: :-[ I am making a very ugly looking plane that I expect will fly very well. Instead of using a radio control system, I'm going to use adjustable timers and PWM for its electric engine's speed and elevator control: 1) Full power for about 15 seconds for its...
  17. audioguru2

    LED questions

  18. audioguru2

    LED questions

    Hi Nikolas, Your circuit feeds the LED very little current. The 555 has an output voltage loss of about 1.4V and the IR LED has a forward voltage drop of about 1.2V, so the resulting voltage across the 1k current-limiting resistor is 3.4V and the current is 3.4mA with a 6V supply, and 9.4mA with...
  19. audioguru2

    OFFSET NULL ADJUSTMENT

    Hi Bjorn, A 741 could have an input offset voltage as high as 10mV. If it is used as a DC amplifier with a gain of 1000 for a sensor or something then its output voltage could be 10V without a signal. You could null the offset voltage with a pot or you could replace the old 741 with a modern...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Horray Ta, I'm glad you fixed it and it is working well. ;D Do you have a 'scope and an accurate dmm? I hope you don't mind thoroughly measuring its performance and posting it.
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