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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

  2. audioguru2

    help me with this computation

    Maxim and TI make volume control ICs that use MCU control. Then you'll need to make your own A to D converter for the MCU to sense the levels.
  3. audioguru2

    3 way speaker system

    Designing the crossover filtering is your biggestproblem. Are you still going to cascade six 6dB/octave RC bandpass filters without using a Butterworth or Linkwitz-Riley design? Then the response of the filters will be very droopy and the system won't work. For example, look at the bandpass...
  4. audioguru2

    Electronic Stethoscope

    Oh yeah, I forgot to say that I used the headphones that came with my pretty good Kenwood portable CD player. Their bass is awesome. ;D
  5. audioguru2

    Wireless intercom

    If they all operate on the same frequency and they are all trying to talk to each other then each will hear a lot of interference between them. Radios can't receive more than 1 transmitter at a time without interference. If the FM receiver is excellent then its good capture ratio will capture...
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi again Helder, You didn't say so I looked: Farnell in Portugal have lots of OPA445AP opamps. ;D
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    The project has always had a -5.6V negative supply. U2 and U3 won't work properly without it. If you measure only 40V from pin 4 to pin 7 and your positive supply is 39.7V then your negative supply isn't working. Check the polarity of its diodes. Actually, since the opamps get hot then they are...
  8. audioguru2

    Electronic Stethoscope

    Hi Duke, The total gain of my project is 272. U1a has 8.5 which is more than I thought because the impedance of the mic is a little lower than I thought. U1b has 1.6 and U5 has 20. I don't know where your bursts of static noise is coming from. On other circuits you could separate the stages but...
  9. audioguru2

    Wireless intercom

    Then each unit will need 3 radio receivers , wouldn't they? Is that hard? The one that transmits music to the other 3 intercoms would need 3 transmitters, wouldn't it?
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Helder, 2 of the opamps have a positive supply voltage of your 39.7V plus the negative supply of -5.6V = 45.3V. The NE5534D has a tiny surface-mount package (the "D") and has an absolute max supply voltage of only 40V. It has diodes across its inputs and its offset adjustment is completely...
  11. audioguru2

    Electronic Stethoscope

    Hi Duke, I heard my heartbeat loud and clear, too loud. See your doc because maybe you have a weak heart. ;D Did you build the 2nd project? Did you substitute any parts? Please describe the random noise you hear. I heard movement of the mic and my dog barking and a phone ringing in the next...
  12. audioguru2

    Audioguru FM Tx

    I don't trust Spice so I don't use it. You need to understand exactly what it is saying. Some things are for the transistor alone, and other things are for the entire circuit. Sometimes the model of a transistor from a manufacturer is incorrect. A Spice sim on another electronics chat site has a...
  13. audioguru2

    Audioguru FM Tx

    Close enough, who cares? Close enough, who cares? Correct. Impedance and Hfe is for AC, resistance and hFE is for DC. Go to http://www.fairchildsemi.com/ds/2N/2N3904.pdf and download their newest datasheet. A divider to base current ratio of 10:1 is good and a higher ratio is a little better if...
  14. audioguru2

    Simple LED strobe

    Hi Um...Me, Have you seen my chaser projects? They aren't simple because they sequence 10 LEDs. They have a pot for blinking speed and another pot for brightness. Their battery seems to last "forever": http://www.electronics-lab.com/projects/games/003/index.html...
  15. audioguru2

    Electronic Memory!

    It's a can of worms. A huge cap is expensive. A rechargable battery might not fully charge but might work. My new car shuts-off the stereo if I open the door with the engine off. It shuts-off after about 10 minutes with the engine off but if I don't open a door (right in the middle of a...
  16. audioguru2

    help me with this computation

    Hi Nolram, I'm glad you abandoned the obsolete project that is wired wrong. A very good Fast Audio Peak Limiter project is here: http://www.sound.westhost.com/project67.htm
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Your fully loaded transformer produces 26.7VAC which could be 28VAC without much load. Its peak voltage will be 39.6V then is reduced by the rectifier bridge to 38.2VDC without much load and is the positive supply for 2 of the opamps. These opamps also have a negative supply of about -5.6V so...
  18. audioguru2

    Electronic Memory!

    I don't believe that a CD-drive uses a whopping 23W. A huge expensive 10F to 30F capacitor could power it for a second or two through a diode. Or it needs a rechargable battery. Is it connected to something that is powered all the time including during starting the engine? The car battery...
  19. audioguru2

    motion sensor help

    Hi Slapjack, Welcome to our forum. ;D Did you lookup Motion Detector at www.howstuffworks.com ? Or Motion Detector Theory at www.google.com ?
  20. audioguru2

    What does Complementary Means?

    An audio power amplifier needs a push-pull output stage. It can use two identical NPN transistors or a complimentary pair with an NPN for one transistor and a PNP transistor for the other. An NPN is complimentary to the PNP. ;D
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