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  1. audioguru2

    Led display Digital Voltmeter question

    You should use the circuit in the datasheet. Circuit (a) is similar to it. It has a max of only a 200mV loss.
  2. audioguru2

    Electronic Stethoscope

    Hi Priyank, Welcome to our forum. ;D I fixed problems with the original Electronic Stethoscope project. My Electronic Stethoscope-2 project uses common cheap parts and is simple to make. Why don't you try it? http://www.electronics-lab.com/projects/science/019/index.html
  3. audioguru2

    Power supply for amps

    The noise from these excellent IC amplifiers is so low that you would hardly hear it, and it would be all the time, not just with signal. The gain is only 23 and is recommended. The pcb layout and supply bypass capacitors are very important to prevent the IC from oscillating, which could occur...
  4. audioguru2

    Led display Digital Voltmeter question

    Hi Vicious, You want the current-measuring resistance to be as low as possible. You don't want to lose too much voltage across it nor ruin voltage regulation. The IC is capable of providing a full-scale voltage of only 200mV but the Smart Kit version has 2.0V. Then if you use the Smart Kit...
  5. audioguru2

    Power supply for amps

    Two 50W amplifiers will need a transformer of at least 143VA so the 160VA transformer will be fine. Two 4700uF capacitors would be the minimum value for 1 amplifier. Use two 10,000uF capacitors for the stereo amplifier. The voltage to the bridge rectifier is the peak of 18V which is only...
  6. audioguru2

    Power supply for amps

    A transformer that is 18-0-18 will make a positive and negative 23.4VDC supply. The LM3886 will give about 50W to a 4 ohm speaker.
  7. audioguru2

    Converter LED to LCD

    I have already said, "An LCD display needs a completely different circuit than an LED display. It might be easier and cheaper to buy a new one." I also said that an LCD multimeter can be purchased for only $10.00CAN. You can see the difference on the datasheet...
  8. audioguru2

    tv signal amplifier

  9. audioguru2

    audioguru fm transmitter

    I don't know what the military or secret police do. Maybe they shoot people or cut off the heads of people who transmit without a licence. ;D
  10. audioguru2

    Converter LED to LCD

    Thanks RDL, that is the same as what I have been saying. Nametc3 started this topic because he can't see his LED display in sunshine, so he wants to convert it to an LCD display that can be seen.
  11. audioguru2

    Power supply for amps

    The datasheet shows an LM3886 with a positive and negative 28VDC supply feeding 68W to a 4 ohm speaker. Amplifier ICs are about 70% efficient, so two amplifiers will draw 194VA from a transformer. A 21-0-21 transformer will make positive and negative 28VDC.
  12. audioguru2

    Power supply for amps

    You won't have anything to limit the power to only 40W. You won't even know when the power reaches only 40W. If the supply voltage is too high for the amplifier's load then the current will also be too high. Voltage times current= power. Power makes the amplifier IC get hot. The heatsink with a...
  13. audioguru2

    Power supply for amps

    Correct. With a positive and negative 28VDC supply, that is made with a 21-0-21 transformer. It would try to protect itself if the volume is high. It might be destroyed or just sound very bad. When it sounds bad then it might blow a tweeter. The transformer would be overloaded if it supplies two...
  14. audioguru2

    Has anybody heard from Staigen?

    How did you make the marquee run backwards?? Now mine also runs backwards. A couple of years ago I think they ran in the other direction.
  15. audioguru2

    Has anybody heard from Staigen?

    I chatted with Staigen on MSN yesterday. His computer was broken but maybe is fixed now and he has been very busy.
  16. audioguru2

    6v charger regulator

    There is your problem.
  17. audioguru2

    Low-pass Filter?

    Transistors work better when they have a power supply, don't they? Yes, the opamp is a voltage follower. With a square-wave input it has a square-wave output. A square-wave is not linear and the level is so high that the output of the opamp saturates with it.
  18. audioguru2

    Power supply for amps

    The LM3876 is designed to drive an 8 ohm speaker, not the 4 ohm speaker you said you will use. An LM3876 is a power amp, not a little opamp. His circuit uses a couple of 680 ohm resistors feeding 15V zener diodes to power a dual opamp for a preamp or something. Yes, the lower is the degrees/W...
  19. audioguru2

    Hi! Has anyone tried this great intercom circuit?

    That is nice and simple. How do you keep the bees out? Did ZomBiE's intercom go 20 Miles or 20 meters? Didn't it pick up a lot of mains hum without him using shielded cable for it?
  20. audioguru2

    Power supply for amps

    The LM3886 with a dual 28V power supply and driving a 4 ohm speaker with 68W is about as easy a circuit as it gets, and works extremely well. I doubt that you will hear any difference in loudness between the 68W amp and a 100W amp. Your hearing's response to loudness is logarithmic, so 10 times...
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