Search results

  1. audioguru2

    Speaker buzzing

    Hi Yevgeni, Of course you can eliminate the hum. Just use shielded audio cable to connect the computer to the input of the amplified speakers. All audio amplifier systems use shielded cables to eliminate hum and other interference. ;D
  2. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Maximus, You need a radio circuit with many tuned circuits, transistors and ICs, not this simple untuned single transistor detector circuit.
  3. audioguru2

    newb transistor question

    Hi Kiwi, Before you said the LED stayed on, now you say it doesn't light. Which is it? ??? ??? ??? You say that it lights with 5V on the base, but I think you mean on its 1.8K base resistor, and a 5V supply for its collector's LED. But when you use a 12V supply for the collector's LED, it...
  4. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Jason, Welcome to our forum. The project is just a simple circuit that detects a transmitter by making a tone. When you touch its antenna then you also become its antenna and it picks up more radio and TV stations, taxi cab radios etc. When you move your transmitting cell-phone closer to it...
  5. audioguru2

    newb transistor question

    Hi Kiwi, The LED and its driver transistor don't turn off because the output voltage of the pic doesn't go low enough (0.5V to 0.6V but should be less). You can fix it by adding a resistor from the base to 0V to make a voltage divider with the existing 1.8K resistor, try 1.8K or less. The BC549...
  6. audioguru2

    newb transistor question

    Hi Kiwi, Please post a sketch of your circuit for us to see whether you grounded the transistor's emitter and the LED with its current-limiting resistor is connected to its collector, and a current-limiting resistor is in series with the transistor's base. Instead of switching the LED/resistor...
  7. audioguru2

    Speaker buzzing

    Hi Yevgeni, Goodbye buzz, hello hum! A speaker amplifier's input cable without a shield makes a nice receiving antenna for mains hum, doesn't it? ;D
  8. audioguru2

    Negative charge pump

    Hi Kevin, What are you going to use the negative 13.3V for? ??? Car radio audio amp ICs don't use a negative voltage. ::)
  9. audioguru2

    how to convert AC16V to DC12?

    Hi Gr8, Welcome to our forum. The transformer will produce an output of 16V RMS when it is loaded with 1A, its rating. It will be more with only a 50mA load, maybe as high as 20V or more. You will need to measure its output voltage with a 50mA load. The rectifier's filter capacitor will charge...
  10. audioguru2

    Low noise amplifier

    Hi Srineo, Use an instrumentation amplifier IC from a major semiconductor manufacturer. Their datasheet or application notes should have a good EEG circuit for you.
  11. audioguru2

    2 X 22W Amplifier

    Hi Mukhalled, Your car radio probably already has an amp circuit like this project. Connections: 1) The 4 ohm (full amp power) or 8 ohm (half amp power) speakers for this project must be disconnected from the original radio, and must not be connected to ground (the car's chassis). 2) The input...
  12. audioguru2

    Dome Lamp Dimmer

    Hi Alun, Good, you have made a nice lamp dimmer circuit. Also try it as a DC motor speed control with a reversed diode across the motor.
  13. audioguru2

    Electronic Stethoscope 2

    Hi Hakyman, I recommended a peak detector rectifier circuit to provide only a positive single pulse to your ADC during each heartbeat. The earphones output swings positive and negative and the negative voltage swings will damage your ADC. The direct DC output of the LM386 could swing up to 8V...
  14. audioguru2

    help!

    Yeah, the guitar's processor makes it sound wicked, nasty and baaaaaaaaad!
  15. audioguru2

    Speaker buzzing

    Hi Ante, I covered the entire neck of the CRT in my 'scope with mu-metal to stop nearby transformer and flourescent light ballast interference that showed on its screen. My 'scope is fully enclosed in a grounded steel case and the electro-magnetic interference went right through it! The mu-metal...
  16. audioguru2

    Calculating voltage output of Capacitor in AC Circuit

    Hi Enigna, I also like to operate power transformers lower than their rated current. Have you 'scope'd the secondary of a power transformer that has a rectifier bridge, big filter cap and a fairly heavy load? The peaks of the sine-wave are flat-topped when the rectifier conducts.
  17. audioguru2

    el34

    Yeah, audio fanatics like the 2nd harmonic distortion and the soft clipping from tube amps. Notice the Aopen tubes? Their stamping looks like they were made in Russia in 1969. They will need replacement, what if there are none remaining? Chinese tubes? Remember when even the food store had a...
  18. audioguru2

    LED Chaser 3 x 36

    I gave him these 2 suggestions for what he is looking for.
  19. audioguru2

    Speaker buzzing

    Never mind, Trigger. Your monitor is not causing the buzz. We need to see if Yevgeni's monitor's deflection coils aren't magnetically shielded and therefore is causing his buzz. Yevgeni, Do the speakers still buzz when they are located at least a metre away from your monitor? Do the...
  20. audioguru2

    Calculating voltage output of Capacitor in AC Circuit

    Hi Enigma, Your simple formula for ripple voltage doesn't allow for the source resistance of the transformer. It seems to give an excessive ripple calculation like it is assuming a high resistance transformer. A high-current transformer usually has a pretty good voltage regulation because it...
Top