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  1. Audioguru

    HA13150A Audio Amplifier

    24W with low distortion sounds only a little louder than 12W at low distortion. 120W with low distortion sounds twice as loud as 12W with low distortion. Because our hearing's sensitivity to loudness is logarithmic.
  2. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Please post the schematic with parts values and a photo of the last circuit that did not work.
  3. Audioguru

    HA13150A Audio Amplifier

    Its datasheet shows that it produces low distortion if you keep the output per channel less than about 12W per channel into 4 ohm speakers. Simply turn down the volume until you do not hear any distortion.
  4. Audioguru

    Power Google Home Mini

    If you have 12V at 500mA or more and use a 7805 with capacitors at the google home mini then the google home mini will get 5V and the 7805 will heat with (12V - 0.8V - 5V) x 500mA= 3.1W. The 7805 will need a heatsink that is not enclosed.
  5. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    It will not work. I told you and showed you: 1) L1 must be parallel with its tuning varactor but instead it is wrongly in series with it. 2) The value of C1 is 1 million times too much at 220uF and instead should be 220pF.
  6. Audioguru

    Infrared headphones idea help please

    The signal fed to the tiny speaker in an earpiece is way too small to drive a speaker. It needs a power amplifier.
  7. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Before I wrongly guessed that you are making an FM transmitter. But now I see that you are simulating the oscillator of an FM superheterodyne radio.
  8. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    What do you think is the function of cc and co? Don't you think they must pass signals from 88MHz to 108MHz? Then make their values 220pF. I notice that your capacitor between the base and emitter of the first transistor is extremely high at 220μF which will not pass the VHF signal. Use 220pF...
  9. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    You cannot tune your oscillator because it is completely wrong. Why can't you see and understand the differences?
  10. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Your inductor is series resonant but I think it should be parallel resonant like this:
  11. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    My 88MHz to 108MHz FM transmitter and many others use an ordinary common 2N3904 transistor as its RF oscillator transistor.
  12. Audioguru

    Modify chinese high power LED to emit less light/heat?

    The lifetime rating of the Chinese LEDs is only a little more than 1 year which is a lot less than properly made western LEDs.
  13. Audioguru

    JFET Power Amplifier With Output Transformer

    Your amplifier is very unusual with obsolete Mosfets that have an extremely low threshold voltage and an output transformer.
  14. Audioguru

    The Fathom-Sound Project

    Is the output a rectangular waveform that sounds like a buzzer? Does the frequency change when the temperature of the transistors change?
  15. Audioguru

    Modify chinese high power LED to emit less light/heat?

    Beware. It is a cheap Chinese LED with no datasheet with details about it. Even ebay does not know who makes it.
  16. Audioguru

    Modify chinese high power LED to emit less light/heat?

    The light has 4 power settings but they do not say how to change the power setting.
  17. Audioguru

    JFET Power Amplifier With Output Transformer

    This amplifier uses obsolete Mosfets that have an extremely low gate-source "threshold" voltage. Normal modern Mosfets have a threshold voltage of 2V to 4V for a very low output current of 0.25mA but this 2SK175 Mosfet conducts 100mA for a gate-source voltage of only 0.65V.
  18. Audioguru

    Hi, have anyebody had trouble building the ELENCO 108 AM/FM RADIO KIT

    My cheap clock radio has an output at clipping of about 0.5W into 8 ohms (an LM386 power amp IC with a 9V supply) which is plenty for a bedroom. I never have the amplifier clipping. My 6.5" woofer and dome tweeter are much more efficient and are much louder than the squeaky little 3" speaker...
  19. Audioguru

    JFET Power Amplifier With Output Transformer

    An output transformer that was used 60 years ago should have no DC current in it but have an AC load. Without an AC load then its reflected impedance is close to infinity then the crossover distortion will not show until it is properly loaded.
  20. Audioguru

    Amp for Visaton FR 13 4 ohm speaker

    Half-decent woofer speakers usually have a datasheet with a recommended enclosure design. The "whizzer" cone of your old speaker was used on the cheap speakers of a TV instead of a real dome tweeter and a recommended crossover network design. ebay sells junk. Their amplifiers might use a poor...
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