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  1. Audioguru

    RC Locomotive Horn fitted to Jaguar XF

    Like the immature little boys who make the engines on their cars and motorcycles as loud as is possible, a 152dB locomotive air horn on a car is silly and will bother thousands of people. Common sense says not to do it. A train horn is loud because a train cannot swerve around an obstacle on...
  2. Audioguru

    Questions about Using LM358

    1) The datasheet of the LM358 shows that the inputs do not work if they are within 1.5V from the positive supply. 2) Your 100k pot does nothing and makes the non-inverting input always +5V because it is not a voltage divider that has your disconnected pin connected to ground. 3) We do not know...
  3. Audioguru

    Ultrasonic Transducer Driver adjust frequency

    The datasheet of the ultrasonic transducer will show a graph of its very narrow range of frequencies. Maybe 38kHz to 42kHz.
  4. Audioguru

    Combining 2 audio outputs into 1

    Your circuit combines signals at the output of an amplifier then the speaker has poor damping of its resonances and then it will sound boomy and maybe screachy. Therefore mixing of the signals with resistors or a mixer circuit should be done at the input of the amplifier. When the signals are...
  5. Audioguru

    Transceiver Circuit

    The switch is simple to see what connects to which of its pins. The RF transformer connects to the antenna and the transformer has a tuneable ferrite core. Does your RF transformer have a ferrite core? Have you tried to tune the transformer? Maybe you should buy a pair of cheap walkie talkies...
  6. Audioguru

    Huskyvarna radio ear defenders

    Which amplifier works well? Adafruit or Neoteck?
  7. Audioguru

    Huskyvarna radio ear defenders

    Headphones are wired with a left signal wire, a right signal wire and a ground wire that is common to both left and right. But the Adafruit amplifier and many more amplifiers that operate from a low supply voltage including most car radios have both wires of each speaker driven with signals...
  8. Audioguru

    Huskyvarna radio ear defenders

    The Adafruit speaker amplifier will not work with headphones unless you replace the entire cable of the headphones because each amplifier is BTL. The headphones cable has a common ground for each channel. The Neoteck headphones amplifier produces fairly low 40mW into 16 ohms but if your...
  9. Audioguru

    Huskyvarna radio ear defenders

    When they designed the headphones they did not know that you phone has a low output level. To modify them we need to know if they have an internal amplifier then we need a schematic of it. Then you need an electronic expert to do the modification because the parts are tiny.
  10. Audioguru

    39v 8a Laboratory Power supply circuit, Need Help

    A laboratory power supply does not have this very simple circuit with a few transistors hanging on a high voltage zener diode with no voltage sensing and no corrections. A zener diode voltage rating higher than about 5V increases its voltage as it heats up. The 39V zener in the schematic...
  11. Audioguru

    39v 8a Laboratory Power supply circuit, Need Help

    It does not regulate the voltage much because it is missing an opamp as an error amplifier with feedback. The base-emitter voltage of the transistors change as they heat and change with load current. The 39V zener diode's voltage changes as it warms up and also changes a little when its load...
  12. Audioguru

    Transceiver Circuit

    The potentiometer adjusts the level of your voice when you transmit. The RF transistor is a crystal oscillator during transmit and is a super-regen circuit (not a mixer) during receive. A simple super-regen circuit is used as the radio receiver in children's radio controlled toys. The very...
  13. Audioguru

    Transceiver Circuit

    A potentiometer is a resistor with a slider (the arrow) that you can slide along the resistance. You can move the slider anywhere from one end to the other end of the resistance or anywhere in between. Take a potentiometer apart to see the resistance and the slider.
  14. Audioguru

    Power bank with bluetooth speaker - power draw issues.

    The woofer from a 2.1 speaker system probably sounds awful by itself which is why it uses a crossover network to prevent the highs from shrieking from the woofer and uses a tweeter for the high frequencies. The stereo PAM8403 IC produces 3 Whats per channel into 4 ohm speakers. Whats are with...
  15. Audioguru

    Transceiver Circuit

    The arrow above the 39nF capacitor is the slider of a 10k ohms potentiometer. It is used only when the switch is in the Transmit mode. What do you think it adjusts?
  16. Audioguru

    Transceiver Circuit

    This is how the switch works:
  17. Audioguru

    Fidget Spinner Generator :)

    A coreless coil captures all of the flux from a nearby VHF radio signal not from the very low frequency of your spinning magnets. A DC motor with a permanent magnet makes an excellent generator and the magnets pull on the cores which "brakes" it when it has no load.
  18. Audioguru

    Fidget Spinner Generator :)

    Why doesn't your coil have a core? With a core it will be much more powerful. Put the fidget in a vacuum with no load on the generator then it will spin a little longer.
  19. Audioguru

    Powering my project with a 7.4v battery

    The 20,000mAh 7.4V Li-PO battery has a protection circuit. Then all you need is a Li-Po battery charger circuit for it.
  20. Audioguru

    9v Guitar Amp w/out LM386

    Aren't electric geetars played at full blast with tons of overdrive distortion? They never turn down the level (they like the awful fuzz sounds). The input of the amplifier has a log volume control.
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