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  1. audioguru2

    Input signal for LM3915. need help.

    The opamp that feeds the average detector is a half-wave rectifier because without signal its output is at 0V. The average detector has its rise and fall times the same and its response is slow so its output is the average of sounds picked up by the microphone. Peak sound levels must be allowed...
  2. audioguru2

    Wattage lowering

    Its ad says, "72 watts x 4 peak power". Peak power is double the normal power which is 36 Watts x 4. But they don't say how much the amps are overdriven since they don't say the distortion so the power per channel at clipping could be only 14 Watts. Most car amps produce 14 Watts per channel at...
  3. audioguru2

    Wattage lowering

    I doubt that your stereo puts out 72 Watts per channel. It is probably 72 Whats per channel. Audio-video stores sell cheap L-Pad attenuators for speakers that soon burn out, and pretty good stepped transformers for adjusting the volume of speakers far from the amplifier. Use a stepped...
  4. audioguru2

    Electronic Stethoscope

  5. audioguru2

    best voltage and current regulator

    Why do you need 6 LEDs? A single ultra-bright white, blue or green LED will shine down the street or across the street at night. If you reduce the current then the battery will last a long time but the light won't be bright. You can use a Cmos gate IC to make a fast oscillator to blink an LED...
  6. audioguru2

    best voltage and current regulator

    The MAX660 is a high current voltage doubler. With a brand new 3V battery powering three 3.6V white LEDs through the three 1N4148 diodes, the light will be extremely bright and the battery's current will be very high for a few minutes if the LEDs don't fail due to over-current. Then the...
  7. audioguru2

    Electronic Stethoscope

    Do your headphones sound like the low frequencies are missing like your recording does? I made part of the circuit and my headphones made my heart sound like thump-thump, thump-thump etc, with a very low frequency.
  8. audioguru2

    best voltage and current regulator

    Use bigger battery cells, C or D cells instead of little AA cells.
  9. audioguru2

    Electronic Stethoscope

    Solder and a shield won't fix low frequencies that are missing. Did you make this one?
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    No. Your transformer will provide only 3.4AAC, so the supply will provide only 2.4ADC instead of 3A. Yes. Not yet. Your transformer doesn't have enough output current so the current setting pot should have a trimpot added in series with it and adjusted so that this project can supply a max...
  11. audioguru2

    Low-pass Filter?

    Connect parts to protect the CD4047 like this:
  12. audioguru2

    Electronic Stethoscope

    Hi TriGerminal, Welcome to our forum. ;D I couldn't make your video play but the sound file is very strange, it is missing the very low frequencies that are produced by heartbeats. The original project has errors on its schematic and in its parts list and might sound something like yours...
  13. audioguru2

    Low-pass Filter?

    A CD4047 is destroyed much quicker than a fuse can blow. It is a supply voltage spike that causes the damage. A fuse slowly protects against current overload. The very low impedance of a car battery as a supply for the project has proven to keep supply voltage spikes down. The addition of a...
  14. audioguru2

    Transistor BF 494

  15. audioguru2

    Transistor BF 494

    I think Mettula needs an entire Veronica FM transmitter kit, if it is still available.
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    A parallel R is an AC load on the transformer and will drop the voltage only when the current and heating is so high that the transformer is grossly overloaded. You need to parallel the secondary windings to get 3.4A AC. A 20VAC transformer will give about 22VAC without a load and about 29.7VDC...
  17. audioguru2

    best voltage and current regulator

    Each LED might draw 20mA to 25mA. Therefore 6 will draw up to 150mA which is a lot of current for AA cells. The current would be less if the LEDs were in series or if they are blinking like in my Ultra-bright Chaser projects.
  18. audioguru2

    Electronic Stethoscope

    A heartbeat is a DC pulse of energy. Sometimes something is caused to vibrate at a very low frequency by the pulse. I don't know what vibrates, the skin maybe?
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Unregulated will be 40.0VDC at 2.3A at full load to about 44VDC without a load. The negative 5.6V supply is additional for the supply to the opamps. Your opamp's supply is 44V + 5.6V=49.6V. It is way too high for ordinary opamps with a 36V max rating and also too high for opamps with a 44V...
  20. audioguru2

    Low-pass Filter?

    On the datasheet it shows that it must be wired that way to oscillate. The LM358 is a dual current amplifier. The output current from Cmos logic devices like a CD4047 is very low. They are current amplifiers. The transformer is used push-pull.
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