Search results

Search Forums New Posts
  1. Audioguru

    PNP Transistor to Drive LED

    A transistor normally has its collector-base junction reverse biased. The datasheet lists its maximum allowed voltage that is MUCH higher than the emitter-base maximum allowed reverse voltage. The emitter-base junction has avalanche breakdown (conducting like a zener diode) when its maximum...
  2. Audioguru

    Grow box led light power?

    The ceiling lamp is powered from 220-240VAC but isn't the DC 12V 6A adaptor also powered from 220-240VAC? Then connect both of them to the same AC power cable.
  3. Audioguru

    PNP Transistor to Drive LED

    Vebo is the maximum allowed reverse voltage that will never happen in this circuit. The PNP transistors in your circuit are emitter-followers with a 0.7V voltage loss, not as switches that saturate. When the PIC output goes low then the LED will light. The LED turns off if the PIC output is high...
  4. Audioguru

    9v Guitar Amp w/out LM386

    Multisim is taught by old teachers. Most of us use the modern LTspiceXVII sim program. All my stripboard prototypes worked perfectly and were sold as the final project.
  5. Audioguru

    9v Guitar Amp w/out LM386

    I gave up using solderless breadboard years ago when the many rows of contacts and wires all over the place picked up interference or caused oscillation and the intermittent contacts caused many problems. I use stripboard instead. The copper strips are cut to length with a drill bit so that a...
  6. Audioguru

    9v Guitar Amp w/out LM386

    Solderless breadboards cause so many problems on these forums.
  7. Audioguru

    High pass filter

    I have seen a capacitor in series with a very cheap little cone speaker used as a tweeter. When the capacitor cuts frequencies below 2kHz then the speaker's resonance at 200Hz is at -20dB and is not too obtrusive. But using a capacitor in series with a woofer at 50Hz will not do much. 50Hz will...
  8. Audioguru

    High pass filter

    A single capacitor makes a very poor filter because the slope is very gradual. A speaker crossover filter uses one or two capacitors plus one or two inductors for up to 4 times the slope. The accuracy if the capacitor value can be 5% or 10%. An active filter circuit works better.
  9. Audioguru

    Please help with Kinetic Audio Amp

    The schematic shows where the wires should be connected. The switch on the jack is shown when no plug is inserted thyen the top jack is 8 ohms. When a plug is inserted into the bottom jack then it becomes 4 ohms and the top jack is disconnected.
  10. Audioguru

    Please help with Kinetic Audio Amp

    On the schematic why did they write "f.b." instead of the clear word "feedback"? You need to feed a high current signal into the wires on the output transformer to calculate the impedance which is difficult. Instead simply measure the resistance to ground of each output. 4 ohms will be the...
  11. Audioguru

    9v Guitar Amp w/out LM386

    Bootstrapping strongly reduces distortion, increases maximum output level and increases gain. I show it with the same input level but with and without the bootstrap capacitor. Then I show the distortion caused when the input level is increased but the output is not clipping yet.
  12. Audioguru

    9v Guitar Amp w/out LM386

    You are using weak and old transistors. The solderless breadboard and alligator clips also might not be able to pass the current.
  13. Audioguru

    9v Guitar Amp w/out LM386

    You do not show any transistor part numbers. The 470μF output capacitor reduces the output at 40Hz. Use 2200μF for frequency response down to 40Hz to be almost flat when the speaker is 8 ohms. Maybe your peak input is 500mV, not 500mA. With your schematic in my simulation then the top and...
  14. Audioguru

    Float Charger

    When the charging current causes a voltage of more than about 0.7V across the 1.2 ohm resistor (0.7V/1.2 ohm= 583mA) then the transistor turns on and drops the regulator voltage which limits the current. The horrible circuit does not detect that a battery is fully charged then it over-charges...
  15. Audioguru

    9v Guitar Amp w/out LM386

    R5 and R6 help to match the output transistors. They can be removed if the transistors are matched. The peak output current is 463mA which causes a voltage drop of 0.15V across each 0.33 ohm resistor.
  16. Audioguru

    Question about my android, it's charging but not through the DC plug only through the USB port

    Any 5VDC power supply will charge the tablet if its connector has the correct polarity and enough current.
  17. Audioguru

    9v Guitar Amp w/out LM386

    It is easy to fix the problems:
  18. Audioguru

    Specific IC s used in solar circuit

    None of the solar garden lights sold at Walmart, Home Depot, Dollarama and Canadian Tire has an old LDR. I posted schematics of modern ICs used in them that do not use an old LDR.
  19. Audioguru

    9v Guitar Amp w/out LM386

    The performance of this simple amplifier is horrible:
  20. Audioguru

    9v Guitar Amp w/out LM386

    The loudness is low because the maximum power in the speaker is puny, about 0.25W like a cheap clock radio. It will be a little louder if the output transistors are replaced and the supply voltage is increased. The 3.3 ohm values of the emitter resistors for the output transistors are much too...
Top