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  1. Audioguru

    Pnp bjt

    Yes, when it turns on.
  2. Audioguru

    FM Pulse Counting Circuit Sounds Bad

    If both C16 and C17 are making de-emphasis then it is too much and cuts highs like your stereo with its treble tone control turned all the way down. Some deaf people like maybe the designer of that circuit cannot hear the difference between 3kHz AM bandwidth and 15kHz FM. But the resistors and...
  3. Audioguru

    FM Pulse Counting Circuit Sounds Bad

    All FM radio stations have first-order pre-emphasis (50μs in the UK) so all FM radios need matching de-emphasis. C16, C17 and maybe others cut high frequencies in that circuit. It looks like the feedback is DC for AGC, not for audio.
  4. Audioguru

    Super capacitor phone battery

    Graphene is used in Li-Po batteries today and it is an improvement over the old kind.
  5. Audioguru

    Pnp bjt

    In this circuit I do not see how the PNP collector voltage can be more positive than the +40V emitter voltage. But if it exceeds about +46V the collector-base junction will be forward biased and the base-emitter junction will be reverse biased and will break down which damages the transistor.
  6. Audioguru

    5v Voltage Regulator Help

    First of all, 9VAC has a peak of 12.7V and the bridge rectifier will drop about 2V when loaded so the input to the regulator will be 10.7V, not 9V. When the circuit is fixed the regulator will heat with 11.5W, overheat, then shutdown. The value of the smoothing capacitor is too low for 1.5A...
  7. Audioguru

    Hartung amplifier project

    This is your thread about the headphones amplifier so put your questions here and they might be answered.
  8. Audioguru

    Hartung amplifier project

    Toob amplifiers muffle the highs a little (but this headphones amp does not have an output transformer that cuts the highs) and makes very low frequencies "loose" instead of tight because they produce poor damping. The "warm" sound is the added even harmonics distortion.
  9. Audioguru

    Hartung amplifier project

    The circuit is probably 100years old. Why make it today?
  10. Audioguru

    Using $1 stereo amp in mono mode

    Usually an amplifier output is one wire with the signal and the other wire is ground. But this little amplifier has bridged outputs so both speaker wires have signal but they are opposing phase so the output voltage swing is doubled which results in almost 4 times the power of a single output...
  11. Audioguru

    Using $1 stereo amp in mono mode

    The PAM8403 datasheet says the speaker can be 4 ohms or 8 ohms. Yours is 3 ohms which is close to a dead short. The amplifier protects itself from a shorted output by disconnecting its output which might happen with your 3 ohm speaker. Or the amplifier might overheat. Connect the two wires...
  12. Audioguru

    Using $1 stereo amp in mono mode

    The amplifier has bridged outputs that already have a "+" amp and a "-" amp. You cannot get more power than it already produces. If you connect a speaker to L+ and R- then the speaker produces half the left channel level mixed with half the right channel level. Half plus half= 1 so you gain...
  13. Audioguru

    3V battery circuit / back lit rocker switches

    The datasheet for the switch has no details: 1) Is the illumination done with a light bulb or with an LED? What color? 2) Is the switch illuminated all the time, or only when it is off, or only when it is on? 3) Are the switch contacts rated for only 12V or is the light bulb 12V? 4) What is the...
  14. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    You need to learn about Ohm's Law. If the output signal voltage to a speaker is 5VAC then when the speaker is 5 ohms the current is 5V/5ohms= 1A and the power is 5V x 1A= 5W. But if the speaker is 10 ohms then the current is half and the power is half at 2.5W. We do not know the output signal...
  15. Audioguru

    Opamp to pic a/d

    Is the A/D on the PIC measuring AC? Does it matter if maximum signal levels of the AC are clipping? Is it OK to rectify the signal so that no signal produces 0V, medium signal produces +2V and maximum signal produces +4V?
  16. Audioguru

    12v bipolar square wave oscillator

    Have you tried a CD4047 oscillator with a digital frequency divider? Its frequency divider produces a perfectly symmetrical 50%-50% squarewave. Its datasheet shows parts values for up to 1MHz. Its frequency accuracy depends on the R and C and a little on the temperature. Its output level...
  17. Audioguru

    What is recommended charger output voltage for a 3V rechargeable AA cell?

    Ni-Cad battery cells are extremely toxic (Cadmium is very poisonous) and are obsolete. They have been replaced by Ni-MH long ago. There is no such thing as a Ni-Cad 3V cell. A cell is 1.4V to 1.5V when fully charged but a discharge averages 1.2V. You must limit the charging current. You also...
  18. Audioguru

    Opamp to pic a/d

    Your opamp output must not exceed the maximum allowed input voltage of the PIC, it must not go negative and it must not go above the positive supply voltage of the PIC. Few opamps operate at such low power supply voltages (maybe 5V powered rail-to-rail opamp will be fine) so you will probably...
  19. Audioguru

    15 v power cord

    Here you said you need 15V but at Digikey you said you want 12V. Why the difference?
  20. Audioguru

    15 v power cord

    Does the mixer need 15VAC or 15VDC? They are completely different and the mixer will probably blow up if the wrong one is used. If it uses DC is the polarity correct? If the polarity (positive wire and negative wire) is backwards then the mixer will probably blow up.
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