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  1. Audioguru

    1W audio power amplifier driven by electret ?

    Sound level drops 6dB per doubling of distance. OOps, I see my error. It should be 86dB at 1m, 80dB at 2M, 74db at 4M and 68dB at 8m. 68dB is almost conversation level. A tiny speaker probably has a peak at a few kHz that the sensitivity is based on (a beeper). If your circuit or your hearing...
  2. Audioguru

    EMG amplifier circuit.

    He does not understand how coupling capacitors prevent amplification of DC input offset voltage. He did not read about ECG amplifiers that cancel common-mode interference signals picked up by the patient and produced by his muscles.
  3. Audioguru

    1W audio power amplifier driven by electret ?

    A 2" speaker can barely produce an adult male voice frequencies, maybe a woman's voice. A half decent 3" speaker (clock radio style) has a sensitivity of about 86dB per Watt at a distance of 1m. 80dB at 2m, 74dB at 2m, 68dB at 4m and only 62dB at 8m. The listening location better be dead quiet...
  4. Audioguru

    1W audio power amplifier driven by electret ?

    Fixed high gain will cause the low power amplifier and maybe the preamp to have clipping with a squarewave buzz for an output whenever the input level is higher than average. What is the input signal? A voice (at conversation level about 10cm away from the mic)?
  5. Audioguru

    MOSFET Power Calculation

    The gate draws no DC current (static) because it is a capacitor. Its current is charging and discharging that capacitor (dynamic) so you need to know its capacitance and the speed and frequency it is charged and discharged.
  6. Audioguru

    MOSFET Power Calculation

    The IRFS4010 Mosfet you are using is not rated for the 4.5V gate voltage you have, instead it is rated for a 10V gate voltage so some will work poorly and get very hot. You cannot order one that works with a 4.5V gate voltage but some might work but you might not find one. Use a "logic level"...
  7. Audioguru

    Wiring LEDs to Corresponding Switches?

    Since ebay knows nothing about electricity, the current required by the button LEDs is not stated. I went to the manufacturer's site but there is no part number box there. I think the cheap Chinese switches have a current rating that is much too high at 25A then they will fail (tarnish and...
  8. Audioguru

    1W audio power amplifier driven by electret ?

    The amps you linked to produce higher output power when they are clipping like crazy with 10% and even at 1% distortion. The PAM8302 class-D power amplifier IC even produces non-hifi distortion when its output power is reduced to 0.1W. The amplifier ICs with "class-H boost" have datasheets that...
  9. Audioguru

    1W audio power amplifier driven by electret ?

    A 4V supply can power a single amplifier that could produce an output of 0.1W into 8 ohms just before clipping (one channel of an obsolete TDA2822M). If two channels are bridged then the output is about 0.3W. A little arithmetic shows that for 1W into 8 ohms then the speaker needs 2.828V RMS...
  10. Audioguru

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

    I can "see" the weight of that powerful transformer.
  11. Audioguru

    PWM frequency generator for LED's

    I use some LM3914 and 74HC4017 ICs to do LED patterns like that. Some of them fade a few following LEDs.
  12. Audioguru

    Which other transistors can I use

    An old VU meter showed average signal levels and let clipping and its severe distortion to occur. My circuit uses a very fast responding peak detector instead.
  13. Audioguru

    Which other transistors can I use

    I have a VU meter project that I posted almost 12 years ago at www.electronics-lab.com . It uses a logarithmic LM3915 bar graph IC with a peak detector and AGC that I designed to increase is range to 50dB. Its microphone is very sensitive and it has a rechargeable 9V battery so it can be...
  14. Audioguru

    Need a solution for a sensitive sound sensor

    The Chinese products have horrible Engrish translations. They are very cheeeeep. The VU meter has no audio specifications. The microphone sensor also has no audio specifications but uses an LM393 dual comparator instead of amplifying the very low level mic signal with a transistor or opamp...
  15. Audioguru

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

    When a filter capacitor is connected with a length of cable then the resistance and inductance of the cable causes poor high frequency filtering to the circuit which might cause voltage spikes or oscillation. The 0.1uF ceramic capacitor on the pcb provides excellent high frequency filtering that...
  16. Audioguru

    Which other transistors can I use

    The microphone on my FM transmitter is the small electret one in my daughter's first cell phone about 20 years ago. It still has its rubber boot. Today it is in the VU meter in my family room.
  17. Audioguru

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

    Put a 0.1uF ceramic capacitor on the board then your 12000uF capacitor will be fine with 18AWG wires 100mm long. Imagine how much ripple there was with an output of 3A when the capacitor was the original little 3300uF. A Chinese unbranded 3300uF would be 1500uF or 1000uF? Have you seen the video...
  18. Audioguru

    Need a solution for a sensitive sound sensor

    The photos of your mic and VU-meter boards show no specifications and no schematics so we do not have a clue about sensitivity and how to increase it. Please post links to their datasheets or to the seller's ad.
  19. Audioguru

    Need a solution for a sensitive sound sensor

    Don't some new cars have a "stealth" coating so that they cannot be seen? It replaces having black glass. No, the opposite. I saw a new car with a very shiny gold metal exterior (Beiber has chrome) and it blinds you or a camera. The sound system blasts RAP so loud that you do not know where the...
  20. Audioguru

    Need a solution for a sensitive sound sensor

    You provided no specifications or schematics of the cheap circuits you bought. All cars produce noise from their tires but the noise is almost the same as leaves rustling or rain so filters will not work. It would be easy to increase sensitivity if the schematics and parts layouts are shown.
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