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  1. Audioguru

    Help With Circuit

    Your schematic is completely wrong if an N-channel Mosfet is used as a follower. Even the negative feedback to the opamp from the drain of the Mosfet becomes positive feedback instead of negative feedback.
  2. Audioguru

    Two stage class A amplifier

    Your emitter resistor bypass capacitors C2 and C3 have their value too small so they are attenuating the 27kHz signal but are passing the fast acting higher frequency pop at full amplification. I increased their value from 0.1uF to 1uF and now the pop has less level than the signal. Your C3 is...
  3. Audioguru

    Two stage class A amplifier

    I tried simulating your circuit and it worked perfectly but I cannot read your "tran" on your post. You have a start delay of 0.1m that I have never used. The simulation is not real because its capacitors are already charged when the sim begins.
  4. Audioguru

    Can't identify LED

    The LEDs have or might have (Chinese you know) a voltage of 3.2V to 3.4V and a current of 10mA to 20mA (ebay is just guessing). Then you can use a 5V supply and connect each one in series with a resistor of (5V - 3.2V)/20mA= 90 ohms (use 91 ohms).If the LEDs are actually 3.4V then their current...
  5. Audioguru

    OPA in mic preamp

    I typed my last reply then copied it and went back to page 1 to see the schematic. My copied text "took over and replaced" my reply that I posted yesterday so that reply and its attached schematic is now gone. Weird.
  6. Audioguru

    OPA in mic preamp

    Is your dual opamp an RC5532 or something else? Did you try another RC5532? Did you try another audio dual opamp? Did you build the circuit on a solderless breadboard that has intermittent contacts? tryt soldering everything together on a pcb or a compact stripboard layout. Your input capacitor...
  7. Audioguru

    Two stage class A amplifier

    Why is the value of C4 500 times the values of C2 and C3? Why are all the resistor values so low causing their currents and the transistor currents (and heating) to be so high?
  8. Audioguru

    Can't identify LED

    The first video is titled Red Green LEDs and clearly shows each LED switching from red to green to red to green over and over, no blue. The second video has the LEDs too far away to see what they are doing. I think they are red blue bicolor LEDs.
  9. Audioguru

    Can't identify LED

    An RGB color changing LED has a microprocessor inside to change the 3 colors. Its program is fixed and cannot be changed. Some cheap Chinese tea-lights, solar garden lights and Christmas ornaments use them. They are completely different to the red-green bi-color LED.
  10. Audioguru

    OPA in mic preamp

    I wonder if "raising" is a bad translation of acoustical feedback howling or squealing? It is simple to fix it, turn down the volume or separate the mic from the speaker.
  11. Audioguru

    OPA in mic preamp

    The circuit is a standard amplifier using the opamp with a single polarity supply. It already has a mid rail reference. I have built hundreds of them but I always filter the voltage source of the mid rail reference voltage to prevent the opamp from amplifying noise on the main supply voltage. C3...
  12. Audioguru

    OPA in mic preamp

    I showed you the formula for calculating the value of the coupling capacitors. The capacitors pass AC but block DC. The value of the capacitor depends on the low cutoff frequency you want and the resistance. For example for a 30Hz cutoff frequency into an 8 ohm speaker the coupling capacitor...
  13. Audioguru

    OPA in mic preamp

    The lowest audio frequency is 20Hz but many speakers cannot go that low. We feel lower frequencies as vibrations. The formula for a capacitor that feeds a resistance is 1 divided by 2 x pi x RC so the frequency where the response begins to reduce for your 10uf capacitor feeding the 10k resistor...
  14. Audioguru

    Should I be able to use this battery with these LED's?

    The LEDs spec a maximum allowed voltage of 14.8V but the battery has 4 cells that are each fully charged to 4.2V then the maximum battery voltage is too high at 16.8V. The battery voltage averages 14.8V when it is half-discharged. The battery is lithium rechargeable and it is destroyed if it...
  15. Audioguru

    Can't identify LED

    Most electronic parts distributors list and stock bi-color LEDs. The LEDs are wired back-to-back with reversed polarity on one so the polarity causes the color change. Here is one from Digikey:
  16. Audioguru

    OPA in mic preamp

    The 5532 and many other opamps work perfectly in that circuit that uses a single positive supply (not a dual polarity supply), is biased properly at half the supply voltage and has the input, output and feedback resistor to ground capacitor-coupled. I noticed that the values for the coupling...
  17. Audioguru

    Vibrating Metronome Project

    An ordinary 555 has plenty of output current to drive a vibration motor but its minimum supply is 4.5V. A vibration motor uses a current that is too high for a small battery. A small motor with a weight is listed at using 200mA (!) and a tiny "coin" vibration motor uses 100mA.
  18. Audioguru

    Special Project with led and motors

    The motor spins much too fast. The LEDs do not have any spec's about their brightness and their viewing angle.
  19. Audioguru

    Christmas tree lights

    When the light is dimmer then the current and heating are less and the bulbs should last longer. When does a light bulb usually burn out? When first turned on because of the huge surge of current into the reduced resistance. If you can find a suitable NTC resistance to put in series then they...
  20. Audioguru

    Trouble making high pass filter

    Your input signal level is 60V peak! Try it with 1V peak.
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