Search results

Search Forums New Posts
  1. Audioguru

    Simple Low Frequency Sound Generator

    Why do you think the 3.5mm jack on your phone has enough output power to drive a low impedance loudspeaker? Instead it has low output power to drive higher impedance earphones. Are you trying to make the entire scull vibrate back and forth? Maybe you need a small transducer that is designed to...
  2. Audioguru

    Simple Low Frequency Sound Generator

    Most small 3-4 in. diameter speakers are 8 ohms. 10W into 8 ohms is 9V RMS which is 25.6V peak-to-peak. An amplifier can produce it when its power supply is about 28.5V and its current is about 0.6A. Not a disposable battery. A bridged amplifier needs a 14.4V at 1.2A supply to produce 10W into 8...
  3. Audioguru

    Problem with usb mp3 kid player project

    A resistor does not simply reduce the voltage. The resistor reduces the current that the amplifier needs then the reduced current reduces the voltage. Please post a schematic of how you connected everything together. Maybe your PAM amplifier is missing input coupling capacitors or resistors.
  4. Audioguru

    Hello, varactor(varicap) formula help

    Why do you want to try measuring such a tiny amount of capacitance? It is 0.00000000001 micro-farads.
  5. Audioguru

    Microphone and camera using same power sounds like crap

    Ask the manufacturer of the mic how it can be powered with an LM317 that has its - common to the audio ground.
  6. Audioguru

    Microphone and camera using same power sounds like crap

    The electret mic that is powered from an AA battery cell is different from an ordinary 2-wires electret mic that needs a resistor from its output to a positive voltage so that the Jfet can draw about 0.5mA. the battery powered mic probably uses a 3-wires electret mic with its Jfet as a...
  7. Audioguru

    Microphone and camera using same power sounds like crap

    You cannot make the output of a 7805 go less than 5V. Use an LM317 to make 1.5V.
  8. Audioguru

    Simple Passive Stereo Mixer

    Each input (resistor) on a passive mixer reduces the output volume. Also each input has the other inputs mixed with it. Also the volume changes if an input or more is disconnected. Changing the resistor value makes no difference. If you use one opamp as an inverting mixer then the gain is the...
  9. Audioguru

    Problem with usb mp3 kid player project

    The 7805 with proper input and output capacitors is fine. Where and why did you add "some resistor"?
  10. Audioguru

    Microphone and camera using same power sounds like crap

    You can't hear the 150kHz noise from the switching regulator but it might beat with the frequency of the second or third regulator or any digital encoder or decoder you are using.
  11. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    A tap on the transformer is still connected to the power supply so it is not isolated.
  12. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The OLED power meter seems to be complicated to use. If you use a separate power supply to power it then you must guess how much current it needs.
  13. Audioguru

    Powering a wireless door chime transmitter.

    What is "a power pack"? A battery lets the transmitter be portable. A wall wart power supply must be plugged in and does not have a regulated output voltage that might be 18V with the small amount of power used by the transmitter. 18V is much too high. We don't know if your transmitter will...
  14. Audioguru

    Microphone and camera using same power sounds like crap

    You never said the part number of the voltage regulator, its input and output voltages and the input and output capacitor values. You say there is more than one voltage regulator. Why? When posting, there is a button that says, "Upload a file" which is where you browse the schematic on your...
  15. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    An LCD display draws very little current (used in a watch powered continuously for months from a button battery) but it has a few LEDs that use some current. The Banggood display is powered from the voltage it is measuring so its minimum supply is 6.5V. Banggood, ebay and Amazon all had their...
  16. Audioguru

    Problem with usb mp3 kid player project

    The absolute maximum power supply voltage for the PAM8403 is 6.0V. Your 230V to 6VAC transformer output might be 7V or 8V AC when not at its full load then the peak is 8V x 1.414= 11.3V and the rectifier bridge reduces it to 9.5V which might destroy the PAM8403 amplifier.
  17. Audioguru

    Forum Category Feedback

    The catagories listing is very different today. It will take some time for me to get used to it.
  18. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    One 2N3055 is mounted beside the bridge rectifier and the BD139 making it hotter than the 2N3055 transistor by itself? Measure the resistance of the leads on your multimeter and subtract its resistance from the 0.6 ohms you measure for each resistor. I had a meter that did that calculation when...
  19. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Both 2N3055 transistors should be doing the same amount of work passing the same amount of current and having the same voltage across them. So of course they should be at almost the same warmth. Your cold one ain't doing anything.
  20. Audioguru

    30W LED amplifier from 12V

    The 12V pulses feeding the LED strips can be attenuated to 10V then used to turn a Mosfet on and off that turns on and off the about 25V power supply that feeds a current limiting circuit for each color in each LED. You burned out an LED because Ali-express sells cheap Chinese junk.
Top