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  1. Audioguru

    Why did connecting this resistor to Jfet gate make the circuit work?

    You are using an opamp with a problem instead of using a real comparator. The TL07x and TL08x have a problem called Opamp Phase Inversion where the output suddenly goes high if an input voltage gets within about 4V from the negative supply. Then the resistor slows this down so maybe it happens...
  2. Audioguru

    Can I use 12 Ohms instead of 8 Ohms speaker?

    Speakers in series sound boomy because their resonance is not damped by the extremely low output impedance of a modern solid state amplifier.
  3. Audioguru

    Components Buyers Guide [for Dummies]

    Your tiny inductor is like the very low current ones in a solar garden light and it will saturate then melt in your circuit.
  4. Audioguru

    Why did connecting this resistor to Jfet gate make the circuit work?

    But you have only -4.5V so the of the Jfet needs -7.5V then it will conduct much more than 200nA. The original circuit that you linked on your other thread about it shows a different Jfet (2N5457) that is cutoff with about 5V max. and has a -10V signal to make sure it is completely turned off...
  5. Audioguru

    LED circuit Heat

    I do not believe that your 5mm LEDs will survive a continuous current of 100mA without melting. Ohms Law says that 1.6V/16 ohms is 100mA. 1.6V/15 ohms is 107mA. There is no 17 ohms but 18 ohms gives a current of 1.6V/18 ohms= 89mA. You said you used 10 ohms so your current was 1.6V/10 ohms=...
  6. Audioguru

    Why did connecting this resistor to Jfet gate make the circuit work?

    The datasheet for a 2N3819 Jfet shows that some of them are still turned on a little (200nA) when the gate-source voltage is -7.5V and yours is only -4.5V. The Jfet has drain-source and drain-gate capacitance that takes time to discharge through a gate resistance as high as 10M ohms.
  7. Audioguru

    Sound module

    Powered by a 3.7V battery, an obsolete TDA2822M dual amplifier IC connected bridged to an 8 ohm speaker provduces only 0.3W which is less than a cheap clock radio. Modern bridged audio amplifiers from Texas Instruments provide 0.6W into an 8 ohm speaker but the IC is so small that you can...
  8. Audioguru

    LED circuit Heat

    What is 100mA? The recommended current or the absolute maximum current if you cool the LED somehow? Do you realize that your 10 ohm resistors are killing the LEDs with 60% more current? How will you cool the LEDs? Please post their datasheet and part number.
  9. Audioguru

    12v car barrery to 6v to run led lighting and 6v radio incorperating a solar pannel

    You di not understand that the trickle charger supplies only a small amount of power. It is designed to supply only the small loss of charge an unused battery loses each day. If you use only a trickle amount of light and only a trickle amount of radio each day then you can use the trickle...
  10. Audioguru

    Testing Piezo Diaphragm fo wristwatch

    A piezo transducer is usually mounted in an enclosure that resonates at the 5kHz resonant frequency of the transducer. It needs a few volts of AC at the resonant frequency, not DC. Your laptop has a microphone input, not a microphone output. A headphones output might drive the transducer if the...
  11. Audioguru

    LED circuit Heat

    No. The LEDs produce the infrared, not the resistors. The IR LEDs are 1.3V each so eight of them in series need 10.4V. The supply is 12V so the LEDs and 10 ohm current-limiting resistor have a current of (12V - 10.4V)/10 ohms= 160mA and the resistor dissipates 160mA squared x 10 ohms= 256mW...
  12. Audioguru

    TV transmitter - picture slides vertically

    I think the video signal into the transmitter must have a high enough level for the diode "DC restorer" to do its job of keeping the video-plus-sync DC level fairly constant as the video contrast changes. Because video-plus-sync is supposed to be DC coupled. If black in the video turns grey...
  13. Audioguru

    Schematic to breadboard

    Some Instructables are designed by kids who are only 10 years old and know nothing about electronics. T1 is turned on and acts like a diode. Since T1 is turned on then T2 is turned off and does nothing. With T1 acting like a diode then the circuit is a very simple "crystal" AM radio. The...
  14. Audioguru

    RGB LEDs dancing on music problem

    A level controller is always a voltage divider. A series potentiometer is called a rheostat and adjusts the current which can be much too high, not the voltage. Maybe you got the original circuit from An Instructable that was designed by a kid 10 years old who knows nothing about electronics...
  15. Audioguru

    RGB LEDs dancing on music problem

    You should do it like this:
  16. Audioguru

    RGB LEDs dancing on music problem

    The LM386 amplifiers are overloaded by the base-emitter diode of the transistors so a series base resistor (try 100 ohms) should be added. The base-emitter diode will charge the input capacitor until the transistor is biased off then it does not work. Add a diode with reversed polarity from...
  17. Audioguru

    Headphones from amp speaker wires

    A soldering iron tip that is too hot incinerates the rosin flux in the solder and builds corrosion on the tip and wires. It makes it difficult for a solder joint to be made. Mine at the correct temperature allows the rosin flux to do its job and each solder joint takes only 1 second.
  18. Audioguru

    5v from 12v is this viable?

    If you make an audio power amplifier you should do it correctly:
  19. Audioguru

    Headphones from amp speaker wires

    I have a Weller soldering iron that is about 52 years old. It has controlled temperature so its tip is always at the correct temperature. It makes soldering very easy and its tip lasts a very long time. They still make it. I tell people who are learning how to solder to "drip" the melted solder...
  20. Audioguru

    Headphones from amp speaker wires

    I am glad to see that you have it working. If your soldering iron melts things then maybe it does not have controlled temperature so it gets too hot, or your solder does not have flux in it.
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